Post on 25-Jun-2022
Draft version October 30, 2018Preprint typeset using LATEX style emulateapj v. 12/16/11
MID-INFRARED PROPERTIES OF NEARBY LUMINOUS INFRARED GALAXIES I: SPITZER IRS SPECTRAFOR THE GOALS SAMPLE
S. Stierwalt1,2, L. Armus1, J.A. Surace1, H. Inami1,3, A.O. Petric1,4, T. Diaz-Santos1, S. Haan1,5, V.Charmandaris6,7, J. Howell1, D.C. Kim8, J. Marshall1, J.M. Mazzarella9, H.W.W. Spoon10, S. Veilleux11, A.Evans2,8, D. B. Sanders12, P. Appleton13, G. Bothun14, C.R. Bridge4, B. Chan9, D. Frayer15, K. Iwasawa16, L.J.Kewley12, S. Lord9, B.F. Madore17, J.E. Melbourne4, E.J. Murphy17, J.A. Rich12, B. Schulz13, E. Sturm18, V.
U12, T. Vavilkin19, K. Xu9
Draft version October 30, 2018
ABSTRACT
The Great Observatories All-Sky LIRG Survey (GOALS) is a comprehensive, multiwavelength studyof luminous infrared galaxies (LIRGs) in the local universe. Here we present low resolution SpitzerIRS spectra covering 5-38µm and provide a basic analysis of the mid-IR spectral properties observedfor nearby LIRGs. In a companion paper, we discuss detailed fits to the spectra and compare theLIRGs to other classes of galaxies. The GOALS sample of 244 nuclei in 180 luminous (1011 ≤LIR/L� < 1012) and 22 ultraluminous (LIR/L� ≥ 1012) IR galaxies represents a complete subsetof the IRAS Revised Bright Galaxy Sample and covers a range of merger stages, morphologies andspectral types. The majority (>60%) of the GOALS LIRGs have high 6.2µm PAH equivalent widths(EQW6.2µm > 0.4µm) and low levels of silicate absorption (s9.7µm > -1.0). There is a general trendamong the U/LIRGs for both silicate depth and mid-infrared (MIR) slope to increase with increasingLIR. U/LIRGs in the late to final stages of a merger also have, on average, steeper MIR slopes andhigher levels of dust obscuration. Together, these trends suggest that as gas & dust is funneled towardsthe center of a coalescing merger, the nuclei become more compact and more obscured. As a result,the dust temperature increases leading also to a steeper MIR slope. The sources that depart fromthese correlations have very low PAH equivalent width (EQW6.2µm < 0.1µm) consistent with theiremission being dominated by an AGN in the MIR. These extremely low PAH equivalent width sourcesseparate into two distinct types: relatively unobscured sources with a very hot dust component (andthus very shallow MIR slopes) and heavily dust obscured nuclei with a steep temperature gradient.The most heavily dust obscured sources are also the most compact in their MIR emission, suggestingthat the obscuring (cool) dust is associated with the outer regions of the starburst and not simply ameasure of the dust along the line of sight through a large, dusty disk. A marked decline is seen forthe fraction of high EQW (star formation dominated) sources as the merger progresses. The decline isaccompanied by an increase in the fraction of composite sources while the fraction of sources where anAGN dominates the MIR emission remains low. When compared to the MIR spectra of submillimetergalaxies (SMGs) at z∼2, both the average GOALS LIRG and ULIRG spectra are more absorbed at9.7µm and the average GOALS LIRG has more PAH emission. However, when the AGN contributionsto both the local GOALS LIRGs and the high-z SMGs are removed, the average local starburstingLIRG closely resembles the starburst-dominated SMGs.
1 Spitzer Science Center, California Institute of Technology,1200 E. California Blvd., Pasadena, CA 91125. e-mail: sabri-nas@virginia.edu
2 Department of Astronomy, University of Virginia, P.O. Box400325, Charlottesville, VA 22904.
3 National Optical Astronomy Observatory, 950 N. CherryAve, Tucson, AZ 85719.
4 Department of Astronomy, California Institute of Technol-ogy, 1200 E. California Blvd., Pasadena, CA 91125.
5 CSIRO Astronomy & Space Science, Marsfield NSW 2122,Australia.
6 Department of Physics and ITCP, University of Crete, GR-71003 Heraklion, Greece.
7 IESL/Foundation for Research and Technology - Hellas, GR-71110, Heraklion, Greece and Chercheur Associe, Observatoirede Paris, F-75014, Paris, France.
8 National Radio Astronomy Observatory, 520 EdgemontRoad, Charlottesville, VA 22903.
9 Infrared Processing & Analysis Center, MS 100-22, Califor-nia Institute of Technology, Pasadena, CA 91125.
10 Department of Astronomy, Cornell University, Ithaca, NY,14853.
11 Astronomy Department, University of Maryland, CollegePark, MD 20742.
12 Institute for Astronomy, University of Hawaii, 2680 Wood-lawn Drive, Honolulu, HI 96825.
13 NASA Herschel Science Center, 770 S. Wilson Ave.,Pasadena, CA 91125.
14 Physics Department, University of Oregon, Eugene, OR97402.
15 National Radio Astronomy Observatory, P.O. Box 2, GreenBank, WV 24944.
16 INAF-Observatorio Astronomico di Bologna, Via Ranzani1, Bologna, Italy.
17 The Observatories, Carnegie Institute of Washington, 813Santa Barbara Street, Pasadena, CA 91101.
18 MPE, Postfach 1312, 85741 Garching Germany.19 Department of Physics and Astronomy, SUNY Stony Brook,
Stony Brook, NY, 11794.
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1. INTRODUCTION
A principal achievement of the Infrared AstronomicalSatellite (IRAS) was the discovery of a large popula-tion of galaxies whose bolometric luminosities were dom-inated by emission in the infrared. At the highest lumi-nosities, local ultraluminous infrared galaxies (ULIRGs;LIR ≥ 1012L�) have been heavily studied (Armus et al.2007; Sanders et al. 1988; Murphy et al. 1996; Spoonet al. 2006; Desai et al. 2007; Rigopoulou et al. 1999;Genzel et al. 1998), and a clear formation picture hasbeen pieced together to explain their extreme emissionin the infrared: more than 90% of local ULIRGs are theproducts of major mergers between molecular gas-richgalaxies. The large amounts of gas that are funneledinto the centers of these mergers lead to intense star for-mation, the feeding of a central AGN, extremely compactreservoirs of molecular gas, and infrared luminosities onthe order of ten times their optical luminosities.
While ULIRGs constitute only 3% of the IRAS RevisedBright Galaxy Sample (RBGS; Sanders et al. 2003), atjust slightly lower luminosities, luminous infrared galax-ies (LIRGs; 1011M� ≤ LIR < 1012M�) make up almost1/3 of the IR sources and have formation histories thatare far less straightforward. In the local universe, thereis evidence that galaxy-galaxy interactions and mergersdrive the large IR luminosities in some LIRGs (Sanders& Mirabel 1996) and many high-z submillimeter galaxies(SMGs) show hints of disturbed optical and radio mor-phologies (Blain et al. 2002; Dasyra et al. 2008). How-ever, at least 20% and as many as 40% of local LIRGsmay have no history of major tidal interactions (How-ell et al., in prep). LIRGs are also represented acrossthe full range of merger stages, unlike ULIRGs which arealmost always at the very end stages of coalescing.
Although LIRGs are relatively rare in the local uni-verse, their comoving number density increases by morethan 100 times from the current epoch to z∼1, (Le Floc’het al. 2005; Magnelli et al. 2009) until LIRGs dominatethe total IR energy density at redshifts of z∼1-2 whenstar formation in the universe was at its peak (Caputiet al. 2007). Piecing together the formation mechanismsand subsequent evolution of these LIRG systems is thusvital to understanding the processes governing star for-mation and black hole accretion, the main sources ofemitting power in the IR.
The Great Observatories All-sky LIRG Survey(GOALS; Armus et al. 2009) represents a complete sub-set of the RBGS comprising 180 LIRGs and 22 ULIRGsand aims to provide a multiwavelength understanding ofthe formation and evolution of local LIRGs as a class ofgalaxy. As part of the Spitzer Legacy survey, a completeset of IR imaging (Infrared Array Camera (IRAC) at3.6, 4.5, 5, and 8µm, and Multiband Imaging Photome-ter (MIPS) at 24, 70, and 160µm) and IR spectroscopyat both high and low resolution (Infrared Spectrograph(IRS) from 5-38µm) is available for the entire sample. Inaddition, imaging in the near-IR/optical (Hubble SpaceTelescope NICMOS and ACS; Haan et al. 2011, Kim etal., in prep), the UV (Galaxy Evolution Explorer near-and far-UV; Howell et al. 2010), and the X-Ray (Chan-dra; Iwasawa et al. 2011) are available for large subsetsof the sample.
In this paper, we present the mid-infrared (MIR) spec-
tra for 244 galaxy nuclei in the 202 nearby GOALSU/LIRG systems taken with the low resolution moduleon the Spitzer Infrared Spectrograph (IRS; Houck et al.2004). The MIR properties derived directly from sucha large, complete sample of LIRG spectra will allow usto place these intermediate-luminosity systems into thecontext of both the extensive previous local ULIRG stud-ies as well as those for lower luminosity, star-forming orstarbursting systems (Brandl et al. 2006; Smith et al.2007b; O’Dowd et al. 2009; Wu et al. 2010).
Full spectral decompositions, including fits to the gasand dust features as well as the SEDs covered by the IRSdata, for the entire sample along with the comparisonof MIR galaxy properties to those at other wavelengthswill be presented in Stierwalt et al. (2013b). The analy-sis presented here focuses on properties derived directlyfrom the MIR spectra. In Section 2, we present the lowresolution MIR spectra observed with the Spitzer IRSShort-Low and Long-Low modules and describe our datareduction methods. In Section 3 we give the distribu-tions of the MIR properties and investigate correlationswith LIR and compactness. In Section 4, we follow eachMIR property through the merging process, and we placeour results into a high redshift context through compar-isons to MIR spectra of submillimeter galaxies at z∼2in Section 5. Finally, our summary and conclusions arepresented in Section 6.
2. OBSERVATIONS & DATA REDUCTION
2.1. The Sample
The GOALS sample consists of 244 galaxy nuclei in180 luminous and 22 ultraluminous nearby IR galaxies.New spectra were obtained using the staring mode for theIRS Short-Low (SL: 5.5-14.5µm) and Long-Low (LL: 14-38µm) modules for 157 galaxies (PID 30323; PI L. Ar-mus). Integration times were determined from nuclearflux densities measured from IRAC and MIPS imagesand range from 45-120 seconds in SL and 30-120 sec-onds in LL. Secondary nuclei were targeted when theMIPS 24µm flux ratio of primary to secondary was ≤5. Archival spectroscopic observations were used for theremaining 45 systems and borrowed most heavily fromstaring program PIDs 105, 3247, & 20549 and mappingprogram PIDs 73, 3269, & 30577.
All 202 systems are nearby but cover a range of dis-tances (15 Mpc < D < 400 Mpc) and so the resultingprojected IRS slit size varies from source to source. Atthe median galaxy distance of 100 Mpc, the nuclear spec-trum covers the central 1.8 kpc in SL and the central 5.2kpc in LL.
2.2. Data Reduction
Staring mode spectroscopic data were reduced usingthe S17 and S18.7 IRS pipelines from the Spitzer ScienceCenter20. For most sources, off-source nods were usedto perform background sky subtraction. In the cases ofmore extended objects, dedicated background pointingswere used to determine the sky surface brightness. Onedimensional spectra were extracted using the standardextraction aperture and point source calibration modesin SPICE21 which employs a tapered extraction aperture
20 http://ssc.spitzer.caltech.edu/irs/features.html21 http://ssc.spitzer.caltech.edu/postbcd/doc/spice.pdf
MIR Properties of Nearby LIRGs 3
that averages roughly to a size of 10.′′6× 36.′′6 in LL and3.′′7× 9.′′5 in SL. After masking bad pixels, multiple nodswere averaged to produce the final spectrum.
Of the archival data, 27 spectra were taken in staringmode and were reduced as described above. For the re-maining 18 systems, spectra were extracted from low res-olution mapping mode data using CUBISM (Smith et al.2007a). Two-dimensional BCDs were assembled, obvi-ous bad pixels were removed and nuclear spectra wereextracted. In two cases (CGCG011-076 and IC1623B),smaller apertures were necessary to avoid other sourcesin the Long-Low maps, but for most sources 2×5 pixelextraction apertures centered on the galaxy’s nucleuswere used to resemble as closely as possible the resultsthat would have been achieved with staring mode ob-servations. However, since the tapered aperture used bySPICE cannot be completely reproduced by the squareapertures in CUBISM, a further mapping-to-staring-mode correction was applied to all spectra derived fromlow resolution archival maps. The correction, a mul-tiplicative factor that is a function of wavelength, wasderived from NGC6240, a star-forming merger remnanttypical of the GOALS sample for which both staring andmapping data were obtained. The correction functionvaries from 1.3 to 2.7 over SL wavelengths and from 1.7to 2.3 over LL wavelengths.
The IRAC 8µm (Channel 4) images for six exam-ple GOALS galaxy nuclei are shown in Figure 1 withthe SL and LL extraction aperture projections overlaid(in the case of staring mode data) or with the CU-BISM extraction windows overlaid (in the case of map-ping mode data). The low resolution IRS spectrum foreach source is also presented along with each MIR image.Spectra for the remainder of the galaxy nuclei, orderedby right ascension, are available as online material andcan also be found at http://goals.ipac.caltech.edu/. Forfive galaxies (IIIZw035, IRASF03359+1523, MCG+08-18-013, IRASF17132+5313, and MCG-01-60-022), thearchival SL staring mode observations were not cen-tered on the galaxy nucleus, so the SL slit overlaysare not shown and the extracted spectra were not usedin our analysis. Complete IRS observations were notavailable for an additional 6 galaxies (no LL spec-tra: NGC2388, NGC4922, and VV705; no SL spectra:IRASF08339+6517; no IRS data: ESO550-IG025 andIC4518). One galaxy (NGC1068; Howell et al. 2007) sat-urates the spectrograph and so is also not shown.
2.3. Scale Factors
For each spectrum a break occurs between the SL andLL modules near 14µm due to the larger LL slit, whichcovers nine times the area covered by the SL slit. Thescale factors required to match the SL flux to the LL fluxare not applied to the spectra in Figures 1 and A1 but arecalculated from the overlap in the SL1 and LL2 modulesand presented in Table 1. Scale factors are not given forany source missing either SL or LL data. For a small mi-nority of cases (CGCG448-020, ESO077-IG014, ESO173-G015, ESO255-IG007, ESO343-IG013, ESO440-IG058(northern nuclei only), IRAS03582+6012, IRASF06076-2139, NGC5653, NGC6090, NGC3690 (western nucleionly), and NGC5256), the scale factor is not given be-cause the placement of the LL slit covered multiple nucleiwhile the smaller SL slit covered only one.
The median scale factors are 1.22 and 1.70 for the star-ing and mapping mode data respectively. The larger me-dian scale factor for mapping data most likely reflects aselection bias toward mapping more extended sources.Twelve scale factors are < 1 (i.e. more flux is recov-ered from SL than from LL), but for all twelve, the scalefactors are also >0.9 and thus represent normal statisti-cal scatter for sources with scale factors near unity. Noclear correlation is observed between the scale factorsand galaxy distance, but at distances > 300 Mpc, a cut-off that includes 6 sources, the scale factors are all <1.2. Similarly, at distances closer than 30 Mpc, there arethree GOALS sources that all have scale factors > 1.6.
The scale factors are applied as a uniform multiplica-tive factor across the entirety of the SL spectra and thusboost equally the PAH fluxes, the continuum, and theabsorption features. Since calculations of the equivalentwidth of the 6.2µm PAH and the depth of the silicatefeature at 9.7µm (EQW6.2µm and s9.7µm; see next sec-tion) both use measurements of feature flux relative tothe continuum, neither are affected by the scaling of theSL spectrum at these low redshifts. The MIR slopes(Fν [30µm]/Fν [15µm]) are also unaffected as they onlyrely on data from the (unscaled) LL portion of the spec-trum.
2.4. s9.7µm, MIR Slope, & EQW6.2µm
Silicate depths at 9.7µm (s9.7µm) were measured di-rectly from the MIR spectra via: sλ = log(fλ/Cλ) wherefλ is the measured flux at the central wavelength of theabsorption feature and Cλ is where the level of the con-tinuum flux would be in the absence of the absorptionfeature, based on an extrapolation to the surroundingcontinuum. Thus, a positive value, sλ > 0, suggestsemission at that wavelength and the deeper the absorp-tion, the lower the s9.7µm value.
The fluxes Fν at 15µm and at 30µm were determinedfrom the average of eight data points surrounding eachwavelength and were then used to calculate the MIRslope. The wavelength regions used fell within ∼14.7-15.4µm for Fν [15µm] and ∼29.5-30.8µm for Fν [30µm].
Equivalent widths for the 6.2µm PAH feature(EQW6.2µm) were measured for each spectrum using themethod outlined in Brandl et al. (2006). Briefly, a splinefit was used to estimate the continuum surrounding the6.2µm PAH feature, and the continuum fit was sub-tracted from the spectrum. In most cases, anchor pointsin determining the continuum were set at 5.15µm <λ <5.31µm, 5.8µm < λ < 5.9µm, 6.5µm < λ < 6.8µm,and 7.1µm< λ < 7.2µm, but each spectrum was visuallyinspected to make sure no features or bad points occurredin these ranges. The PAH flux was then measured usingdirect integration. The 6.2µm feature was selected forthe EQW calculation because, of the five brightest PAHfeatures, it is the least affected by silicate absorption at9.7µm and 18.5µm, and it is not blended with other PAHfeatures. However, in some cases the 6.2µm PAH featurepartially overlaps with the absorption feature due to wa-ter ice at 6.0µm. For those sources found by the spec-tral fitting to have τice >0 (see Stierwalt et al. 2013b),the ice absorption was assumed to affect the underly-ing continuum but not the PAH emission, and the EQWwas calculated accordingly. Four galaxies have only up-per limits placed on their EQW6.2µm: IRAS05223+1908,
4 Stierwalt et al.
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MIR Properties of Nearby LIRGs 5
MCG-03-34-064, NGC4418, and IRAS08572+3015.
2.5. Merger Stages
Merger stages for the entire sample were determinedvia visual inspection of the IRAC 3.6µm (Channel 1) im-ages. Each galaxy was assigned one of the following fivedesignations: ‘N’ for nonmergers (no sign of merger ac-tivity or massive neighbors), ‘a’ for pre-mergers (galaxypairs prior to a first encounter), ‘b’ for early-stage merg-ers (post-first encounter with galaxy disks still symmetricand in tact but with signs of tidal tails), ‘c’ for mid-stage mergers (showing amorphous disks, tidal tails, andother signs of merger activity), or ‘d’ for late-stage merg-ers (two nuclei in a common envelope). Given the res-olution of the IRAC images (∼2′′), late stage mergerscan be easily mistaken for nonmergers in the 3.6-µm im-ages. To alleviate this problem, any galaxies classified asnonmergers or early stage mergers in the IRAC imageswith available higher resolution imaging in the literaturethat clearly showed signs of a late stage major mergerwere changed accordingly. We also use the literature toidentify spectroscopic pairs which resulted in reclassify-ing some nonmergers as pre-mergers.
For a subset of 78 GOALS galaxies (all withlog(LIR/L�) >11.4), we have additional merger classifi-cations based on available HST B, I, and H-band images.The higher resolution of this imaging enables a more de-tailed classification system with more finely tuned mergerstage designations (stages 0 through 6). These mergerstages were already described and presented in Haanet al. (2011), but we reproduce and discuss them here toaid with cross-referencing the two classification schemes.
3. MID-INFRARED PROPERTIES OF NEARBY LIRGS
3.1. LIRG vs ULIRG Distributions
Silicate depths, MIR slopes, PAH equivalent widths,and all associated uncertainties for the GOALS sample,in addition to the SL-to-LL scale factors and mergerstages, are presented in Table 1, and the distributionsof EQW6.2µm,s9.7µm, and MIR slope are shown in Fig-ure 2. The EQW6.2µm and s9.7µm parameters are notgiven for the five sources with off-centered SL spectra,and MIR slopes are not presented for the four sourceswithout available either SL or LL spectra or for the 12sources for which multiple nuclei are observed within theLL slit.
As shown in Figure 2, the majority of LIRGs (63%)are dominated by PAH emission (EQW6.2µm >0.4µm),show little to no silicate absorption (s9.7µm > -1),and have MIR slopes of 4 < Fν [30µm]/Fν [15µm] <10. Only six LIRGs have deep silicate absorptionwith s9.7µm < -1.75 (NGC4418, IRAS03582+6012 E,ESO203-IG001, IRASF10038-3338, IRASF12224-0624,and ESO60-IG016). The remainder of the LIRGs showweak to no silicate absorption with a significant fraction(23%) of LIRGs showing silicates in emission at 9.7µm,including 11% with s9.7µm > 0.15. A few of the LIRGswith s9.7µm > 0 are likely AGN-dominated (EQW6.2µm
< 0.27µm) and thus any absorption at 9.7µm is filledin by an excess of hot dust. However, most are lowerluminosity galaxies with 90% having log(LIR/L�) <11.25. These LIRGs are likely analagous to the unob-scured starburst NGC 7714, a galaxy whose IR emis-
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Fig. 2.— Distributions of MIR spectral parameters (upper pan-els). Top: silicate strength at 9.7µm, Middle: logarithm of MIRslope, and Bottom: equivalent width of the 6.2µm PAH feature.On average, GOALS ULIRGs (filled red histograms) have deepersilicate absorption depths, steeper MIR slopes, andlower equivalentwidths than the GOALS sample as a whole (white histograms).The lower panel on each plot shows the same GOALS ULIRG dis-tributions with a smaller y-scale. The filled solid black portionof the lowest bin of the EQW6.2µm histogram represents the foursources for which only upper limits are measured.
sion is fueled almost entirely by star formation (Mar-shall et al. 2007). The silicate strengths in the LIRGshave a median of s9.7µm = -0.25 ± 0.58 and rangefrom the heavily obscured NGC4418 at s9.7µm = -3.51± 0.09 to NGC5395, the southern component of theLIRG system Arp84, which shows silicates in emission
6 Stierwalt et al.
(s9.7µm = 0.52 ± 0.07). Five LIRGs are continuum dom-inated and show at most only weak PAH or line fea-tures (EQW6.2µm < 0.04µm and s9.7µm > -0.2; MCG-03-34-064, IRAS05223+1908, NGC1275, NGC7674, andAM0702-601 N).
While the majority of LIRGs favor the high endof the distribution in both EQW6.2µm and s9.7µm,they are found clustered in an intermediate range ofMIR slopes with a median of Fν [30µm]/Fν [15µm] =7.11±4.74. The MIR slopes measured for the LIRGsrange from Fν [30µm]/Fν [15µm] = 2.00 ± 0.01 inIRAS05223+1908 which shows a near power-law spec-trum in the MIR to Fν [30µm]/Fν [15µm] = 35.40 ± 1.38in IRAS10173+0828.
For those LIRGs with measurable 6.2µm PAH EQWs,the values range from EQW6.2µm = 0.005µm ±0.003µm for the northeastern component of the LIRGpair IRAS03582+6012 to EQW6.2µm = 0.78µm ±0.01µm for the most southeastern of the three galax-ies composing the LIRG system IRAS17578-0400. Thedistribution for all of the GOALS LIRGs has a medianof EQW6.2µm = 0.55µm ±0.18µm. The same medianvalue was found for a sample of lower luminosity star-bursting galaxies (Brandl et al. 2006). Tight limits areplaced on the EQW for the three LIRGs and one ULIRGwithout a 6.2µm PAH detection: IRAS05223+1908 at<0.043µm, MCG-03-34-064 at <0.044µm, NGC4418 at<0.066µm, and IRAS08572+3915 at <0.081µm.
The GOALS ULIRGs, represented by the solid red his-tograms in Figure 2, show a clear offset from the LIRGsin their distributions for all three fundamental proper-ties. The ULIRGs have a higher median flux density ra-tio (Fν [30µm]/Fν [15µm] = 12.54±5.41), a lower medianPAH equivalent width (EQW6.2µm = 0.30µm±0.17µm),and deeper median silicate absorption (s9.7µm = -1.05 ±0.85). The GOALS ULIRGs span nearly the full rangeof MIR slopes covered by LIRGs but are not found withEQW6.2µm >0.52µm or with s9.7µm >-0.15. Comparingthe derived values for the 22 ULIRGs in GOALS with thelarger samples from Spoon et al. (2007) (104 ULIRGs)and Veilleux et al. (2009) (QUEST; 50 ULIRGs), we findthat the larger numbers of ULIRGs in these samples re-sult in a larger spread in MIR properties (i.e. 6.2µmPAH EQWs up to 0.8µm and silicate depths up to 0.2;Spoon et al. (2007)). However, the median values areconsistent with ULIRGs having lower EQW6.2µm, deepers9.7µm, and steeper MIR slope than LIRGs: medianEQW6.2µm = 0.15µm & s9.7µm = -1.47 (Spoon et al.2007) and median Fν [30µm]/Fν [15µm] = 11.6 (Veilleuxet al. 2009).
The results of a Kolmogorov-Smirnov (KS) test giveprobabilities of <0.01% that the chance deviations be-tween the distributions of EQW6.2µm, s9.7µm, and MIRslope for GOALS LIRGs vs ULIRGs are expected to belarger assuming they are derived from the same parentsample. In other words, the two samples are significantlydifferent. These probabilities decrease by several ordersof magnitude when the QUEST and Spoon et al. (2007)ULIRGs are included. When the GOALS ULIRGs arecompared to the larger ULIRG samples, the KS testsuggests the chance deviations in their distributions inMIR slope, EQW6.2µm, and s9.7µm are expected to belarger with probabilities of 80%, 40%, and 30%, i.e. it islikely the GOALS ULIRGs and the Spoon et al. (2007) &
Veilleux et al. (2009) samples are derived from the sameparent sample.
3.2. Correlations with LIR
Figure 3 shows the distributions of s9.7µm, MIR slope,and EQW6.2µm as a function of IR luminosity, LIR. TheIR luminosities for all 202 U/LIRG systems were pre-sented in Armus et al. (2009) and derived using the defi-nitions of Sanders & Mirabel (1996)22. In cases of multi-ple nuclei, the total LIR for the system is divided accord-ing to the ratio of the fluxes at 70µm for each nuclei. Ina small number of cases, 70µm images are not availableand so 24µm flux ratios are used instead.
There is a general trend among the U/LIRGs for bothsilicate depth and MIR slope to increase with increas-ing LIR. The sources that depart from these correla-tions at deep levels of silicate obscuration (top panel) orshallow MIR slopes (middle panel) have, in both cases,very low PAH equivalent width (EQW6.2µm < 0.27µm)and are thus likely dominated by emission from an AGN.Increasingly luminous systems become increasingly dustobscured until a turnover occurs at s9.7µm∼ -1.5, abovewhich the buried AGN candidates show no further cor-relation between s9.7µm and LIR. As LIR decreases, theMIR slopes flatten until Fν [30µm]/Fν [15µm]. 0.5, be-low which the relatively unobscured AGN have high LIRgiven their slopes. ULIRGs have an average EQW6.2µm
that is lower than that for LIRGs, but sources with alarge range of luminosities are found at each equivalentwidth (lower panel) so there is not a tight correlationbetween LIR and EQW6.2µm.
3.3. Disentangling s9.7µm, MIR Slope, & EQW6.2µm
To further disentangle the relationship between the3 main MIR parameters, we examine the s9.7µm andEQW6.2µm versus MIR slope parameter spaces in Figure4. The distribution of s9.7µm with MIR slope is color-coded by EQW6.2µm (panel a) while the distributionof EQW6.2µm with MIR slope is color-coded by s9.7µm(panel b).
In the majority of LIRGs, star formation dominatesthe intense MIR emission and the similar conditions inthe photodissociation regions resulting in this (PAH-dominated) emission lead to similar MIR propertiesamong the bulk of the GOALS sample. In Figure 4a,the majority of GOALS galaxies, those with EQW6.2µm
> 0.27µm (green squares and blue stars), show a roughcorrelation between increasing MIR slope and increasingsilicate depth (lower s9.7µm). The starburst galaxies ofBrandl et al. (2006) which span mostly luminosities be-low 1011L� exhibit a similar relationship between τ9.7µmand Fν [30µm]/Fν [15µm] with the same slope. The trendin Figure 4a suggests that the average dust temperaturerises as a consequence of the nuclei becoming more ob-scured and compact. As the dust temperature increases,the rising portion of the blackbody emission spectrumshifts to shorter wavelengths, and warmer sources haveincreasingly more flux at 30µm as seen for the GOALSU/LIRGs with s9.7µm >-1.5.
22 LIR/L� = 4π(DL[m])2(FIR[Wm−2])/3.826 × 1026[Wm−2]and FIR = 1.8 × 10−14(13.48f12µm + 5.16f25µm + 2.58f60µm +f100µm[Wm−2])
MIR Properties of Nearby LIRGs 7
−4 −3 −2 −1 0 1Silicate Strength (s9.7µ m)
10.0
10.5
11.0
11.5
12.0
12.5
13.0lo
g(L
IR/L
sun)
EQW< 0.27µm
0.27µm<EQW< 0.54µm
EQW >0.54µm
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6log (F
ν[30µm]/F
ν[15µm])
10.0
10.5
11.0
11.5
12.0
12.5
13.0
log
(LIR
/Lsu
n)
EQW< 0.27µm
0.27µm<EQW< 0.54µm
EQW >0.54µm
0.0 0.2 0.4 0.6 0.86.2µm PAH EW (µm)
10.0
10.5
11.0
11.5
12.0
12.5
13.0
log(L
IR/L
sun)
EQW< 0.27µm
0.27µm<EQW< 0.54µm
EQW >0.54µm
Fig. 3.— Distribution of MIR spectral parameters with LIRcolor-coded by EQW6.2µm. Top: silicate strength at 9.7µm, Mid-dle: logarithm of MIR slope, and Bottom: equivalent width ofthe 6.2µm PAH feature. There is a loose trend among LIRGs forincreasing silicate depth and MIR slope with increasing LIR. How-ever, LIRGs span nearly the full range of EQW6.2µm at any givenluminosity.
Most of the sources with low PAH equivalent width,however, do not follow these simple trends in MIR prop-erties. In Figure 4a, these low-EQW sources (red cir-cles) are split roughly into two populations: those thatare relatively unobscured with shallow MIR slopes and
those heavily obscured sources (s9.7µm<-1.5) with steepMIR slopes. A similar split is observed in Figure 4b:for EQW6.2µm <0.27µm, the heavily obscured sources(purple circles) are found at steeper MIR slopes whilethe relatively unobscured sources (magenta circles) arefound at the shallowest flux density ratios.
An increasingly significant hot dust component froman AGN leads both to a decrease in EQW6.2µm andto a flatter MIR slope. For the GOALS sources withthe strongest, relatively unobscured AGN (s9.7µm&-0.6;EQW6.2µm.0.05µm), an upper limit to the MIR slopecan be set at Fν [30µm]/Fν [15µm]<4 from both panelsin Figure 4. These galaxies (including IRAS05223+1908and UGC08058) are represented by the red circles in thelower right corner of panel a and the magenta circles inthe lower left corner of panel b. No other sources arefound with flatter MIR slopes. This limit agrees withthat observed for the starbursts of Brandl et al. (2006)and for the QUEST ULIRGs of Veilleux et al. (2009).Relatively unobscured AGN can thus be identified basedon their low MIR flux density ratio alone.
In the most heavily obscured, low EQW galaxies, how-ever, the MIR continuum slopes are steeper due to theburied, hot source. These galaxies (red circles in theleft half of Figure 4a and purple circles in Figure 4b)have steep MIR slopes for the same reason sources withs9.7µm∼-1.5 in Figure 4a have steep MIR slopes: most ofthe warm dust emission is hidden behind a large amountof cooler dust. A comparison to the 5 mJy UnbiasedSpitzer Extragalactic Survey (5MUSES; Wu et al. 2010)highlights the difference between the low and high s9.7µmsources at low EQW6.2µm. The 5MUSES sample is 24-µm selected (indicating the presence of hot dust) butlacks the heavily obscured sources found in GOALS. Thedistributions for the two samples in Figure 4b are roughlythe same (5MUSES is represented by the dashed line al-though there is significant scatter about this line; see Wuet al. (2010)) - both show the lowest EQW6.2µm sourceshave the shallowest MIR slopes - except 5MUSES lacksthe obscured low EQW6.2µm galaxies (purple circles inFigure 4b).
The apparent strength of the 9.7µm silicate feature(i.e. the depth of the absorption feature that does notaccount for any silicate emission, s9.7µm) is shown versusEQW6.2µm in Figure 5 for GOALS LIRGs (open circles)and ULIRGs (red triangles). No galaxies are observedwith both high equivalent widths and large levels of sili-cate absorption. However, at low equivalent widths, twodistinct branches, similar to those seen by Spoon et al.(2007), emerge that clearly distinguish the lower equiva-lent width (EQW6.2µm < 0.1µm) sources with minimalto no silicate absorption (s9.7µm > -0.5) from those dom-inated by silicate absorption (heavily obscured sources;s9.7µm <-1.75). Sources with intermediate levels of sili-cate absorption are not found at low equivalent widths.
As shown in Figure 5, the highly absorbed sources arenot limited to ULIRGs. At values of s9.7µm < -1.75, theGOALS sample includes five ULIRGs (labeled in Fig-ure 5) as well as the dense, compact nascent starburstLIRG NGC4418 (Spoon et al. 2001; Roussel et al. 2003;Evans et al. 2006) and five additional LIRGs that spana large range of LIRG luminosities: IRASF12224-0624(log(LIR/L�) = 11.36), IRAS03582+6012 (log(LIR/L�)= 11.42), IRASF10038-3338 (log(LIR/L�) = 11.78),
8 Stierwalt et al.
−4 −3 −2 −1 0 Silicate Strength (s9.7µ m)
1
10
100F
ν[3
0µ
m]/
Fν[1
5µ
m]
a)
EQW< 0.27µm0.27µm< EQW< 0.54µmEQW >0.54µm
0.0 0.2 0.4 0.6 0.86.2µm PAH EW (µm)
s9.7µm < −1.5
−0.6 < s9.7µm
−1.5 < s9.7µm < −0.6
b)
Fig. 4.— Distribution of MIR slope (Fν [30µm]/Fν [15µm]) versus a) silicate absorption at 9.7µm color-coded by EQW6.2µm and b)EQW6.2µm color-coded by s9.7µm. GOALS sources with EQW6.2µm >0.27µm (green squares + blue stars in panel a, right side of panelb) show a rough correlation between increasing silicate depth and increasing MIR slope (a) and follow the correlation between EQW6.2µmand MIR slope observed in the 24-µm selected 5MUSES sample (dashed line, b; Wu et al. (2010)). At low EQW (EQW6.2µm <0.27µm;red circles in panel a, left side of panel b), relatively unobscured AGN-dominated sources all have MIR slopes below ∼4. However, atthe deepest levels of silicate absorption (left side of panel a, purple circles in panel b), the MIR slope is no longer a clear indicator oftemperature and so the heavily obscured sources do not follow the trend in panel a, and the location of the 15-µm continuum between the9.7µm and 18.5µm absorption features lead to elevated MIR slopes in panel b. Although far less numerous (only 18% of GOALS nucleihave EQW6.2µm < 0.27µm), the lowest equivalent width sources cover a wider range of LIR, MIR slope, and s9.7µm than those sources ofhigher EQW6.2µm that make up the majority of the sample.
0.01 0.10 1.006.2µm PAH EW (µm)
1
0
−1
−2
−3
−4
Sil
icate
Str
en
gth
(s 9
.7µ
m)
IRAS03582+6012
IRAS08572+3915NGC4418
Mrk231
NGC1275
Arp220
LIRG
ULIRG
Fig. 5.— Equivalent width of the 6.2µm PAH versus silicate strength for the LIRGs (open circles) and ULIRGs (red triangles) of theGOALS sample. The majority (>60%) of the LIRGs are found at EQW6.2µm > 0.4µm and s9.7µm > -1.0, while nearly all ULIRGshave EQW6.2µm < 0.5µm and s9.7µm < -0.5. Sources at low EQW are divided into two distinct branches (silicate-dominated versuscontinuum-dominated).
MIR Properties of Nearby LIRGs 9
ESO60-IG016 (log(LIR/L�) = 11.82), and ESO203-IG001 (log(LIR/L�) = 11.86).
3.4. Compactness
The most heavily obscured nuclei among the GOALSgalaxies are also the most compact: they all show little-to-no MIR emission extending outside of the IRS slit.In Figure 6, the silicate strength is plotted against η, aparameter that represents the fraction of the emission at24µm intercepted by the IRS slit:
η = log(FMIPStot [24µm]/F IRSslit [24µm]) (1)
where FMIPStot [24µm] is the total flux of a source as mea-
sured from its MIPS 24µm image (Mazzarella et al.,in prep) and F IRSslit [24µm] is the flux within the IRS slitderived by convolving the MIPS-24µm filter with thelow resolution IRS spectrum. The most obscured sources(s9.7µm < -1.75) all have η ∼ 0 (i.e. all of the flux mea-sured by the larger MIPS field of view at 24µm is alsorecovered within the much smaller IRS slit).
Although distance effects could act to disguise an ex-tended component in comparisons of total versus intra-slit fluxes if all of the obscured sources were the most dis-tant, the median distance for the heavily obscured, lowη nuclei is only 60% larger than the median distance forthe less obscured sources (190 Mpc vs 115 Mpc) suggest-ing distance alone cannot be driving the difference in η.Even more importantly, the heavily obscured, low η tailof the distribution in Figure 6 includes the two closest,obscured LIRGs, NGC4418 at 36.5 Mpc and s9.7µm =-3.51 ± 0.09 and NGC3690 at 50.7 Mpc and s9.7µm =-1.65± 0.02. Both of these LIRGs would have been easilyresolved had they shown any extended MIR emission.Additionally, the existence of galaxies with high η andlow s9.7µm with distances well above 100 Mpc indicatethat extended sources can still be resolved even at largerdistances.
The fraction of resolved emission within the IRS slit isalso much lower for the obscured sources. The fraction ofextended emission (FEE13.2µm) is defined by Dıaz-Santoset al. (2010) as the fraction of emission within the IRSslit originating outside of the unresolved component (i.e.a point source at that distance). For the most obscuredGOALS nuclei, the average 〈FEE13.2µm〉 = 0.07 com-pared to 〈FEE13.2µm〉 = 0.39 for the remaining (weaklyobscured or unobscured) LIRGs. As discussed in detailin Dıaz-Santos et al. (2010), such a dramatic differencein FEE between obscured and unobscured nuclei cannotbe the result of distance effects alone.
Together the low η, the low FEE13.2µm, and their in-clusion of nearby sources suggest the nuclei in these heav-ily obscured sources dominate the 24-µm emission fromtheir parent galaxies, and so the most heavily obscuredLIRGs and ULIRGs also have the most compact MIRcontinuum emission. Given their low EQW6.2µm, if ex-treme levels of obscuration are not simply masking thePAH emission, the higher densities in these nuclei maycreate an environment where PAH dust grains are notpresent or the conditions are not appropriate for excitingthem (i.e. lacking in photodissociation regions). Alter-natively, the low EQW6.2µm may indicate an increase inthe continuum flux at 6µm due to a rise in dust temper-ature. None of the low η, high s9.7µm nuclei are observed
to be [NeV] emitters (Petric et al. 2011), most likely be-cause their large optical depths obscure any line emissionthat would be present at 14.3µm.
−4 −3 −2 −1 0 1Silicate Strength (s9.7µ m)
0.0
0.5
1.0
1.5
η =
lo
g(F
tot[
24
µm
]/F
sli
t[2
4µ
m])
EQW6.2µm < 0.27µm
0.27µm < EQW6.2µm < 0.54µm
EQW6.2µm > 0.54µm
Fig. 6.— Silicate strength versus η, a measure of the total-to-slitflux ratio at 24µm. GOALS LIRGs and ULIRGs are color codedby 6.2µm PAH equivalent width with low equivalent width (AGN-dominated) sources (EQW6.2µm < 0.27µm) represented by redcircles and high equivalent width (starburst-dominated) sources(EQW6.2µm > 0.54µm) represented by blue stars. Intermedi-ate EQW (composite) sources are shown by orange (0.27µm <EQW6.2µm < 0.41µm) and green (0.41µm < EQW6.2µm <0.54µm) squares. Heavily obscures sources have no extended com-ponent to their 24µm emission (η ∼0).
4. TRACING MIR PROPERTIES THROUGH MERGERSTAGE
In Figure 7, silicate strength, MIR slope, and PAHequivalent width are traced through merger stage forGOALS galaxies. To look for subtle differences in MIRproperties throughout the merging process, we focus ononly those sources that have HST classifications (column11 in Table 1). Since this subset contains only six galax-ies with no indication of a merger (stage 0), we includeall of the nonmergers (Stage N) from the IRAC-basedclassifications (column 10 in Table 1) to derive a moresecure median for each spectral property. Although theHST data samples only LIRGs with log(LIR/L�)>11.4,the dense sampling of merger stages made possible bythe deep, high spatial resolution optical and NIR imagesprovides a much finer look at the spectral changes alongthe merger sequence. Mean values for each merger stageclipped at 3σ are shown in red with their associated stan-dard deviations.
As the mergers progress and gas & dust is funneledtowards the center, galaxies become on average moreobscured with steeper MIR slopes. Silicate depths ofs9.7µm. -1 are only reached at merger stages of 3and later. No LIRG systems in merger stage 1 haveFν [30µm]/Fν [15µm]> 1, while the average MIR slope is>1 for the later stages 4-6. These two results agree withseveral studies finding higher LIR at later merger stagessince, as shown in Figure 3, increasing MIR slope andsilicate depth are also linked to higher LIR in LIRGs.As merging galaxies coalesce, the nuclei become more
10 Stierwalt et al.
compact and more obscured, and, as a result, the dusttemperature increases leading to a steeper MIR slope asdiscussed in Section 3.
N 1 2 3 4 5+6Merger Stage
−3
−2
−1
0
1
Sil
icat
e S
tren
gth
−3
−2
−1
0
1
Sil
icat
e S
tren
gth
N 1 2 3 4 5+6Merger Stage
0.2
0.4
0.6
0.8
1.0
1.2
1.4
log(F
30µ
m/F
15µ
m)
0.2
0.4
0.6
0.8
1.0
1.2
1.4
log(F
30µ
m/F
15µ
m)
N 1 2 3 4 5+6Merger Stage
0.0
0.2
0.4
0.6
0.8
6.2
µm
PA
H E
QW
[µ
m]
0.0
0.2
0.4
0.6
0.8
6.2
µm
PA
H E
QW
[µ
m]
Fig. 7.— MIR properties of GOALS galaxies traced throughmerger stage. Top: silicate strength (s9.7µm), Middle: MIR slope(log(Fν [30µm]/Fν [15µm]), and Bottom: EQW6.2µm. Mergers(Stages 1-6) are represented by the 78 GOALS galaxies for whichhigh resolution HST imaging is available (Haan et al. 2011, ; seeColumn (11) in Table 1). Nonmergers (StageN) are classified usingIRAC 3.6µm images and the literature (see Section 2.5 for details).Mean values for each merger stage clipped at 3σ are shown in redwith their associated standard deviations.
There is some indication that lower PAH equiva-lent widths are favored at later merger stages but thisis mostly dominated by the fact that only starburst-dominated galaxies (EQW6.2µm>0.54µm) are observedin stage 1. (The one exception is southern componentof the LIRG system AM0702-601.) For all other mergerstages, the full range of EQW6.2µm is observed.
A clearer link between PAH equivalent width andmerger stage is observed when galaxies are binned bytheir EQW6.2µm(and thus the likely AGN contributionto the MIR). In Figure 8 the LIRGs are divided intothree EQW6.2µm bins indicating AGN dominated sources(red circles), composite sources (green squares), and star-bursts (blue stars). Starbursts clearly play a dominantrole at early merger stages as was also shown by Pet-ric et al. (2011) and Haan et al. (2011), but the de-cline in the starburst contribution is not balanced by anincrease in AGN-dominated sources. The contributionfrom LIRGs with an AGN dominating in the MIR staysat a roughly constant fraction throughout the mergerprocess, but composite sources (i.e. the weaker AGNthat are not yet entirely dominant over star formation inthe MIR) show a marked increase at later merger stages.This may indicate that the timescales for the AGN tobegin to dominate the MIR emission are longer than themerger timescale (a few hundred million years). In bothFigures 7 and 8, the nonmerging LIRGs cover nearly thefull range of every MIR property investigated.
N 1 2 3 4 5+6Merger Stage
0.0
0.2
0.4
0.6
0.8
1.0
Nu
mb
er F
ract
ion
N 1 2 3 4 5+6
0.0
0.2
0.4
0.6
0.8
1.0EQW < 0.27µm0.27µm < EQW < 0.54µmEQW > 0.54µm
Fig. 8.— Overall AGN fraction (as determined by EQW of the6.2µm PAH) traced through merger stage for the GOALS sample.Merger stages are classified as described in Figure 7. A markeddecline is seen for the fraction of high EQW (star formation domi-nated; blue stars) sources as the merger progresses. This decline isaccompanied by an increased contribution not from the strongestAGN (red circles) which remain low but from the composite sources(i.e. weaker AGN that are not yet entirely dominant over star for-mation in the MIR; green squares).
5. COMPARISONS TO SUBMILLIMETER GALAXIES
The dust-enshrouded, strongly starbursting nature ofLIRGs makes them obvious candidates for possible lo-cal analogs to the dusty submillimeter galaxies (SMGs)that make a significant contribution to the global starformation rate density at higher redshifts. In Figure 9,we compare different subsets of the GOALS MIR spectrawith the average SMG spectra from Menendez-Delmestreet al. (2009) (hereafter M09) derived from a sample of 24SMGs at redshifts of 0.65 < z <3.2. All average spec-tra for both the LIRGs and the SMGs are normalized at6.8µm. In agreement with the conclusions of Desai et al.(2007) and M09, the average local ULIRG spectrum (redline in Figure 9a) is more absorbed than the average SMGspectrum (black line) but has weaker PAH emission. Al-though GOALS LIRGs are less obscured than ULIRGson average, the average LIRG spectrum (dashed line)
MIR Properties of Nearby LIRGs 11
is still more absorbed than the average SMG while alsoshowing stronger PAH emission at 6.2µm, 7.7µm, and11.3µm. Even when the nuclear emission of galaxies isremoved, the spectrum of the extended component ofLIRGs does not resemble that of the total SMG com-posite (Dıaz-Santos et al. 2011). The average local star-burst (blue line; Brandl et al. 2006) shows a similar levelof silicate absorption but much stronger PAH emissioncompared to the average SMG.
0
2
4
6
8
Fν/F
ν[6
.8µ
m]
(Norm
ali
zed) ULIRGs
Starbursts (Brandl+06)
LIRGsSMGs (M09)
a)
6 8 10 12 14λ (µm)
0.51.01.5
Fν/F
ν[S
MG
]
0
2
4
6
8
Fν/F
ν[6
.8µ
m]
(Norm
ali
zed)
AGN LIRGsStarburst LIRGsStarburst SMG (M09)
b)
6 8 10 12 14λ (µm)
0.51.01.5
Fν/F
ν[S
MG
]
Fig. 9.— Comparison of GOALS average LIRG and ULIRGspectra to average submillimeter galaxy spectra from Menendez-Delmestre et al. (2009): a) the composite SMG spectrum (black)is less obscured than the average ULIRG (red) and the averageLIRG (dashed) but has weaker PAH emission than local starbursts(blue). b) after removing the AGN-dominated systems from boththe average SMG and the average LIRG, the average starburstSMG spectrum (black) is well-represented by the starburst LIRGs(EQW6.2µm >0.54µm; blue) but not the AGN-dominated LIRGs(EQW6.2µm <0.27µm; red) with the exception of a feature at∼10.5µm. All average spectra are normalized at λ = 6.8µm andthe shaded gray area represents the 1-σ standard deviation to theaveraged SMG spectrum. Residuals are shown in the bottom pan-els.
The fraction of MIR emission attributed to AGN over-all for the GOALS LIRGs is only 12% (Petric et al. 2011),and M09 observed a contribution of <32% from AGN tothe total bolometric luminosity in SMGs. However, asseen in Figures 1 and A1, those sources dominated byAGN have MIR spectra that are vastly different from
those with strong PAH emission. The low equivalentwidth sources (i.e. those with MIR emission that is mostlikely AGN-dominated) also show a larger scatter in theirMIR properties, as discussed in Section 3. To reduce pos-sible confusion caused by this AGN contribution, we alsocompare the average SMG spectrum for only those SMGswithout AGN indicators in the MIR (i.e starburst SMGswith EQW7.7µm >1µm & αMIR <0.5; M09) to averageLIRG spectra with and without an AGN contribution inFigure 9b.
The average AGN-dominated LIRG spectrum (LIRGswith EQW6.2µm <0.27µm; red line) clearly does notresemble the average starburst SMG (solid black line).However the average starburst-dominated LIRG spectra(EQW6.2µm >0.54µm; blue line) is a better match to theaverage starburst SMG. All three average spectra agreewithin 15% below 10µm (see the residuals in the lowerpanel).
Between 10-11µm, all three average LIRG spectra inFigure 9b agree closely, but no subset of the GOALSLIRGs or ULIRGs reproduces the emission feature ob-served in the average starburst SMG spectrum near10.5µm. Although the feature is also not detected inthe average (low resolution) local starburst spectrum (seeFigure 9a), both the [SIV] emission line at 10.51µm anda PAH feature at 10.60µm are clearly seen in the aver-age of the high resolution IRS spectra of the same star-burst sample (see Figure 4 of Bernard-Salas et al. 2009).The feature detected in the low resolution SMG spec-tra is likely a blend of these two features (Sturm et al.2000; Bernard-Salas et al. 2009; Smith et al. 2007b),but may be dominated by the PAH feature emissionsince it remains faint and unresolved at low resolution.Bernard-Salas et al. (2009) also detect a third feature at10.75µm that they associate with PAH emission due toits close correlation with the 11.3µm PAH which maycontribute to the emission in the SMGs.
6. SUMMARY & CONCLUSIONS
We presented low resolution IRS spectra for 244 galaxynuclei in the GOALS sample of 180 LIRGs and 22ULIRGs. The GOALS galaxies cover a range of spec-tral types, silicate strengths, and merger stages, and rep-resent a complete subset of the IRAS Revised BrightGalaxy Sample. We investigated the MIR propertiesdirectly measured from the spectra and discovered thefollowing:1) Local LIRGs cover a large range of MIR properties andany single LIRG cannot represent the class as a whole.LIRGs span 0.005µm < EQW6.2µm <0.78µm (withnondetections of the 6.2µm PAH reachingEQW6.2µm <0.043µm), -3.51 < s9.7µm < 0.052(with 23% of LIRGs showing silicate emission), and 2.00< Fν [30µm]/Fν [15µm] < 35.40. However, the majority(63%) of LIRGs have EQW6.2µm > 0.4, s9.7µm > -1.0,and MIR slopes in the range of 4 < Fν [30µm]/Fν [15µm]< 10.2) The GOALS ULIRGs span a narrower range of MIRproperties than those covered by the LIRGs. When com-pared to LIRGs, the ULIRGs (LIR > 1012L�) havea steeper median slope (Fν [30µm]/Fν [15µm] = 12.54for the ULIRGs compared to Fν [30µm]/Fν [15µm] =7.11 for the LIRGs), a lower mean equivalent width(EQW6.2µm = 0.30µm versus EQW6.2µm = 0.55µm),
12 Stierwalt et al.
and deeper average silicate absorption (s9.7µm = -1.05versus s9.7µm = -0.25).3) There is a general trend among the U/LIRGs for bothsilicate depth and MIR slope to increase with increasingLIR. As LIR increases, the temperature may rise as aconsequence of the nuclei becoming more obscured andcompact. As the dust temperature increases, the ris-ing portion of the blackbody emission spectrum shifts toshorter wavelengths, and warmer sources have increas-ingly more flux at 30µm, and thus steeper MIR slopes.The sources that depart from these correlations, in bothcases, have very low PAH equivalent width (EQW6.2µm
< 0.1µm) consistent with their MIR emission being dom-inated by an AGN.4) Although less numerous (only 18% of the sample),LIRGs with the largest contributions from AGN (thosewith EQW6.2µm < 0.27µm) cover a wider range of MIRslopes and silicate strengths than those sources of higherequivalent width that make up the majority of the sam-ple. The sources with extremely low PAH equivalentwidths (EQW6.2µm<0.1µm) separate into two distincttypes: relatively unobscured sources with a very hot dustcomponent (and thus very shallow MIR slopes) and heav-ily dust obscured nuclei with a steep temperature gradi-ent. For the AGN-dominated LIRGs with low apparentobscuration, an upper limit to the MIR slope can be setat Fν [30µm]/Fν [15µm]∼4. The most obscured nuclei,however, have steeper MIR slopes due to most of theirwarm dust emission being hidden behind a large amountof cooler dust.
suggesting 5) The LIRGs most likely harboring buriedAGN (the obscured nuclei with s9.7µm<-1.75) all haveEQW6.2µm <0.2µm and lack any extended componentto their MIR emission at 24µm. Extreme levels of dustobscuration may simply be blocking PAH emission, orthe higher densities in these nuclei may create an environ-ment where PAH dust grains are not present or the con-ditions are not appropriate for exciting them (i.e. lackingin photodissociation regions). Their compact nature sug-gests that their obscuring (cool) dust is associated withthe outer regions of the starburst and not simply a mea-
sure of the dust along the line of sight through a large,dusty disk.6) U/LIRGs in the late to final stages of a merger have,on average, steeper MIR slopes and higher levels of dustobscuration. As merging galaxies coalesce and gas & dustis funneled towards the center, the nuclei become morecompact and more obscured. As a result, the dust tem-perature increases leading also to a steeper MIR slope. Amarked decline is seen for the fraction of high EQW (starformation dominated) sources as the merger progresses.The decline is accompanied by an increase in the fractionof composite sources while the fraction of sources wherean AGN dominates the MIR emission remains low.7) Despite their dusty and starbursty nature, the aver-age nearby LIRG spectrum does not resemble the averagecomposite (starburst + AGN) MIR spectrum from sub-millimeter galaxies at z∼2. Both the average LIRG andULIRG spectra are more absorbed at 9.7µm and the av-erage LIRG has more PAH emission. However, once theAGN contributions are removed from the average LIRGand from the average SMG spectra, the PAH emissionand level of silicate absorption of the average spectrumfor starburst-dominated SMGs (i.e. those without AGNspectral signatures; Menendez-Delmestre et al. 2009) arefit well by the average starburst-dominated local LIRG.
The Spitzer Space Telescope is operated by the JetPropulsion Laboratory, California Institute of Technol-ogy, under NASA contract 1407. This research has madeuse of the NASA/IPAC Extragalactic Database (NED)which is operated by the Jet Propulsion Laboratory,California Institute of Technology, under contract withthe National Aeronautics and Space Administration.This research has made use of the NASA/IPAC InfraredScience Archive, which is operated by the Jet Propul-sion Laboratory, California Institute of Technology,under contract with the National Aeronautics SpaceAdministration. We would like to thank M. Cluver formany helpful discussions and K. Menendez-Delmestrefor sharing her average SMG spectra.
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14 Stierwalt et al.
TABLE
1Mid-IR
SpectralParametersfortheGOALSSample
Sou
rceS
hort-L
ow
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ)
Sca
leM
erger
MS
Nam
e[J
2000]
[ ◦]
[J2000]
[ ◦]
[µm
]F
acto
rS
tage
(HS
T)
NG
C0023
00h
09m
53.4
s+
25d
55m
26.3
s(-3
2.8
)00h
09m
53.4
s+
25d
55m
26.3
s(-1
16.6
)0.5
8(0
.01)
0.1
8(0
.04)
6.8
1(0
.04)
1.4
9b
NG
C0034
00h
11m
06.4
s-1
2d
06m
28.7
s(3
5.3
)∗00h
11m
06.5
s-1
2d
06m
29.2
s(1
17.7
)∗0.4
5(0
.02)
-0.7
9(0
.03)
9.9
4(0
.09)
1.7
0d
5A
rp256
00h
18m
50.9
s-1
0d
22m
36.6
s(-3
6.1
)00h
18m
50.9
s-1
0d
22m
36.6
s(-1
19.8
)0.7
2(0
.01)
-0.2
6(0
.03)
6.7
3(0
.07)
1.2
2b
3E
SO
350-IG
038
00h
36m
52.5
s-3
3d
33m
17.1
s(1
63.1
)00h
36m
52.5
s-3
3d
33m
17.0
s(7
9.4
)0.1
5(0
.004)
-0.3
4(0
.02)
4.7
3(0
.01)
1.1
5c
NG
C0232
W00h
42m
45.8
s-2
3d
33m
40.7
s(-4
4.6
)00h
42m
45.8
s-2
3d
33m
40.7
s(-1
28.3
)0.5
5(0
.01)
-0.3
8(0
.03)
7.3
3(0
.03)
1.2
1b
NG
C0232
E00h
42m
52.8
s-2
3d
32m
27.5
s(-4
4.6
)00h
42m
52.8
s-2
3d
32m
27.5
s(-1
28.3
)0.1
6(0
.005)
-0.2
6(0
.03)
3.6
3(0
.03)
1.1
6b
MC
G+
12-0
2-0
01
00h
54m
03.9
s+
73d
05m
06.0
s(7
1.1
)00h
54m
03.9
s+
73d
05m
05.9
s(-1
2.7
)0.6
5(0
.01)
-0.2
4(0
.02)
7.1
9(0
.04)
1.0
8c
3N
GC
0317B
00h
57m
40.4
s+
43d
47m
32.1
s(-2
9.6
)00h
57m
40.4
s+
43d
47m
32.1
s(-1
13.4
)0.5
7(0
.01)
-0.8
6(0
.05)
8.2
3(0
.09)
1.1
5a
IC1623B
01h
07m
47.6
s-1
7d
30m
25.4
s(2
5.4
)∗01h
07m
47.3
s-1
7d
30m
28.4
s(1
9.1
)∗0.3
0(0
.004)
-0.9
8(0
.02)
7.7
1(0
.01)
1.7
3c
3M
CG
-03-0
4-0
14
01h
10m
09.0
s-1
6d
51m
09.6
s(1
50.7
)01h
10m
08.9
s-1
6d
51m
10.6
s(-1
26.8
)0.6
7(0
.01)
-0.0
4(0
.02)
6.9
8(0
.09)
1.1
6N
0E
SO
244-G
012
01h
18m
08.3
s-4
4d
27m
43.5
s(-7
9.0
)01h
18m
08.3
s-4
4d
27m
43.6
s(-1
62.7
)0.6
6(0
.01)
-0.3
2(0
.13)
7.3
9(0
.06)
1.1
9b
CG
CG
436-0
30
01h
20m
02.6
s+
14d
21m
42.7
s(-2
7.1
)01h
20m
02.6
s+
14d
21m
42.7
s(-1
10.9
)0.3
5(0
.01)
-1.1
0(0
.10)
8.9
4(0
.09)
1.1
0b
2E
SO
353-G
020
01h
34m
51.2
s-3
6d
08m
14.5
s(-5
8.4
)01h
34m
51.2
s-3
6d
08m
14.5
s(-1
42.1
)0.5
4(0
.01)
-0.5
8(0
.04)
7.2
6(0
.10)
1.4
2N
RR
032
N01h
36m
23.4
s-3
7d
19m
18.0
s(-5
9.0
)01h
36m
23.4
s-3
7d
19m
18.1
s(-1
42.7
)0.5
2(0
.01)
0.0
9(0
.03)
6.1
9(0
.10)
1.2
8a
RR
032
S01h
36m
24.1
s-3
7d
20m
25.9
s(-5
8.9
)01h
36m
24.1
s-3
7d
20m
25.9
s(-1
42.7
)0.7
0(0
.01)
-0.3
8(0
.04)
6.7
4(0
.09)
1.1
4a
IRA
SF
01364-1
042
01h
38m
52.9
s-1
0d
27m
11.2
s(1
49.2
)01h
38m
52.8
s-1
0d
27m
12.0
s(-1
10.8
)0.3
9(0
.01)
-1.2
7(0
.08)
32.7
2(1
.04)
1.4
1d
5IIIZ
w035
—01h
44m
30.5
s+
17d
06m
08.7
s(-1
09.1
)—
—23.5
2(0
.24)
—a
3N
GC
0695
01h
51m
14.2
s+
22d
34m
56.4
s(-2
3.5
)01h
51m
14.3
s+
22d
34m
55.4
s(-1
07.3
)0.6
5(0
.01)
0.3
1(0
.02)
6.1
7(0
.09)
1.8
6N
UG
C01385
01h
54m
53.8
s+
36d
55m
04.0
s(-2
2.0
)01h
54m
53.8
s+
36d
55m
04.1
s(-1
05.7
)0.6
4(0
.01)
-0.0
0(0
.11)
6.7
3(0
.08)
1.1
2a
NG
C0838
W02h
09m
24.7
s-1
0d
08m
09.6
s(1
62.7
)02h
09m
24.7
s-1
0d
08m
09.5
s(7
8.9
)0.4
5(0
.01)
0.2
7(0
.03)
4.7
6(0
.10)
1.6
3a
NG
C0838
E02h
09m
38.7
s-1
0d
08m
47.5
s(1
62.6
)02h
09m
38.7
s-1
0d
08m
47.5
s(7
8.9
)0.7
4(0
.01)
0.2
3(0
.03)
7.5
9(0
.06)
2.0
0a
NG
C0838
S02h
09m
42.8
s-1
0d
11m
02.3
s(1
62.6
)02h
09m
42.8
s-1
0d
11m
02.3
s(7
8.9
)0.5
0(0
.01)
-0.8
3(0
.03)
6.7
2(0
.04)
1.1
8a
NG
C0828
02h
10m
09.5
s+
39d
11m
24.6
s(-1
9.3
)02h
10m
09.5
s+
39d
11m
24.7
s(-1
03.0
)0.6
1(0
.01)
-0.0
9(0
.03)
5.0
4(0
.05)
1.6
4d
IC0214
02h
14m
05.5
s+
05d
10m
25.4
s(-2
6.2
)02h
14m
05.4
s+
05d
10m
25.4
s(-1
10.0
)0.6
4(0
.01)
-0.0
5(0
.02)
6.5
1(0
.10)
1.3
4d
NG
C0877
S02h
17m
53.2
s+
14d
31m
18.1
s(-2
4.5
)02h
17m
53.2
s+
14d
31m
18.2
s(-1
08.3
)0.4
6(0
.01)
-1.1
6(0
.10)
7.1
1(0
.17)
1.3
6a
NG
C0877
N02h17m
59.7
s+
14d
32m
38.0
s(-2
4.5
)02h
17m
59.6
s+
14d
32m
38.0
s(-1
08.3
)0.3
5(0
.03)
0.1
6(0
.03)
6.1
4(0
.14)
2.1
0a
MC
G+
05-0
6-0
36
S02h
23m
19.0
s+
32d
11m
18.1
s(1
55.4
)02h
23m
19.0
s+
32d
11m
18.2
s(7
1.7
)0.5
4(0
.01)
0.1
9(0
.03)
6.1
2(0
.22)
1.4
6a
2M
CG
+05-0
6-0
36
N02h
23m
22.0
s+
32d
11m
48.4
s(1
55.4
)02h
23m
22.0
s+
32d
11m
48.5
s(7
1.7
)0.4
8(0
.01)
-0.2
5(0
.02)
6.2
3(0
.07)
1.2
9a
2U
GC
01845
02h
24m
08.0
s+
47d
58m
11.8
s(-3
1.2
)02h
24m
08.0
s+
47d
58m
11.9
s(-1
15.0
)0.5
8(0
.01)
-0.4
0(0
.03)
7.7
1(0
.09)
1.1
8N
NG
C0958
02h
30m
42.9
s-0
2d
56m
20.4
s(-2
7.6
)02h
30m
42.9
s-0
2d
56m
20.4
s(-1
11.3
)0.2
9(0
.01)
0.0
0(0
.08)
4.9
6(0
.15)
1.7
7N
MIR Properties of Nearby LIRGs 15
Sou
rce
Sh
ort
-Low
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s 9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ
)S
cale
Mer
ger
MS
Nam
e[J
2000]
[◦]
[J2000]
[◦]
[µm
]F
act
or
Sta
ge
(HS
T)
NG
C0992
02h
37m
25.5
s+
21d
06m
04.4
s(-
21.8
)02h
37m
25.5
s+
21d
06m
04.4
s(-
105.5
)0.7
2(0
.01)
0.0
5(0
.04)
6.4
1(0
.09)
1.2
8c
UG
C02238
02h
46m
17.5
s+
13d
05m
44.3
s(-
24.7
)02h
46m
17.5
s+
13d
05m
44.9
s(-
108.2
)0.6
3(0
.01)
-0.3
7(0
.04)
5.6
6(0
.07)
1.1
4d
IRA
SF
02437+
2122
02h
46m
39.1
s+
21d
35m
10.1
s(-
22.3
)02h
46m
39.1
s+
21d
35m
10.3
s(-
104.0
)0.1
6(0
.01)
-1.2
5(0
.06)
8.8
1(0
.16)
1.0
6c
UG
C02369
02h
54m
01.8
s+
14d
58m
15.4
s(-
22.9
)02h
54m
01.8
s+
14d
58m
15.5
s(-
106.7
)0.5
7(0
.01)
-0.1
1(0
.07)
6.4
8(0
.03)
1.3
0b
3U
GC
02608
N03h
15m
01.5
s+
42d
02m
08.5
s(-
21.8
)03h
15m
01.5
s+
42d
02m
08.6
s(-
105.6
)0.2
0(0
.003)
-0.2
2(0
.02)
5.0
4(0
.02)
1.1
5N
UG
C02608
S03h
15m
14.6
s+
41d
58m
49.9
s(-
21.8
)03h15m
14.6
s+
41d
58m
49.9
s(-
105.5
)0.2
5(0
.14)
0.5
2(0
.32)
4.5
9(1
.60)
1.7
2N
NG
C1275
03h
19m
48.2
s+
41d
30m
41.9
s(1
57.6
)03h
19m
48.2
s+
41d
30m
41.7
s(7
3.8
)0.0
2(0
.003)
0.2
6(0
.02)
2.7
3(0
.01)
1.0
1N
IRA
SF
03217+
4022
03h
25m
05.4
s+
40d
33m
32.3
s(-
22.2
)03h
25m
05.4
s+
40d
33m
32.3
s(-
105.9
)0.5
5(0
.01)
-0.4
7(0
.03)
8.3
4(0
.07)
1.1
7d
NG
C1365
03h
33m
36.4
s-3
6d
08m
26.0
s(-
51.0
)03h
33m
36.4
s-3
6d
08m
25.5
s(7
4.4
)0.1
3(0
.002)
0.1
0(0
.05)
5.6
5(0
.03)
1.6
7N
IRA
SF
03359+
1523
—03h
38m
47.1
s+
15d
32m
53.2
s(-
102.3
)—
—12.4
5(0
.16)
—d
CG
CG
465-0
12
N03h
54m
07.8
s+
15d
59m
24.1
s(-
17.6
)03h
54m
07.8
s+
15d59m
24.2
s(-
101.3
)0.6
7(0
.02)
0.4
3(0
.03)
4.3
3(0
.16)
1.8
3a
CG
CG
465-0
12
S03h
54m
16.1
s+
15d
55m
43.2
s(-
17.6
)03h
54m
16.1
s+
15d
55m
43.3
s(-
101.3
)0.6
0(0
.01)
-0.0
2(0
.03)
6.6
4(0
.66)
1.6
5c
IRA
S03582+
6012
W04h
02m
32.0
s+
60d
20m
38.3
s(-
12.6
)04h
02m
32.0
s+
60d
20m
38.3
s(-
96.3
)0.6
4(0
.01)
0.0
8(0
.04)
8.8
0(0
.08)
—c
IRA
S03582+
6012
E04h
02m
33.0
s+
60d
20m
41.8
s(-
12.6
)04h
02m
33.0
s+
60d
20m
41.8
s(-
96.3
)0.0
1(0
.003)
-3.0
4(0
.03)
6.3
9(0
.02)
—c
UG
C02982
04h
12m
22.6
s+
05d
32m
50.5
s(-
15.8
)04h
12m
22.6
s+
05d
32m
50.5
s(-
99.6
)0.6
8(0
.01)
0.1
8(0
.03)
5.1
1(0
.06)
2.0
2d
ES
O420-G
013
04h
13m
49.7
s-3
2d
00m
25.5
s(-
49.4
)04h
13m
49.7
s-3
2d
00m
25.5
s(-
133.2
)0.3
0(0
.003)
-0.2
7(0
.03)
5.4
3(0
.04)
1.2
1N
NG
C1572
04h
22m
42.8
s-4
0d
36m
03.6
s(-
131.6
)04h
22m
42.8
s-4
0d
36m
03.6
s(1
44.7
)0.4
6(0
.01)
-0.1
6(0
.03)
6.7
6(0
.08)
1.2
0N
IRA
S04271+
3849
04h
30m
33.1
s+
38d
55m
48.0
s(-
10.8
)04h
30m
33.1
s+
38d
55m
48.0
s(-
94.5
)0.6
1(0
.01)
-0.2
9(0
.04)
7.8
5(0
.12)
1.2
5d
NG
C1614
04h
33m
59.8
s-0
8d
34m
43.1
s(-
26.7
)04h
33m
59.8
s-0
8d
34m
40.8
s(-
110.4
)0.6
1(0
.01)
-0.4
1(0
.02)
4.8
1(0
.01)
1.4
0d
5U
GC
03094
04h
35m
33.9
s+
19d
10m
18.3
s(1
67.0
)04h
35m
33.8
s+
19d
10m
17.5
s(-
97.5
)0.4
3(0
.005)
-0.3
2(0
.02)
5.0
5(0
.06)
1.1
6N
ES
O203-I
G001
04h
46m
49.5
s-4
8d
33m
30.1
s(-
106.3
)04h
46m
49.5
s-4
8d
33m
30.1
s(1
70.0
)0.0
3(0
.01)
-3.2
0(0
.17)
15.0
5(0
.33)
0.9
8d
3M
CG
-05-1
2-0
06
04h
52m
05.0
s-3
2d
59m
27.1
s(-
141.0
)04h
52m
05.0
s-3
2d
59m
27.0
s(1
35.3
)0.5
3(0
.01)
-0.0
2(0
.03)
7.2
5(0
.07)
1.1
1N
NG
C1797
05h
07m
44.8
s-0
8d
01m
08.7
s(-
18.8
)05h
07m
44.8
s-0
8d
01m
08.7
s(-
102.5
)0.6
2(0
.01)
-0.2
0(0
.03)
7.7
2(0
.08)
1.3
0a
CG
CG
468-0
02
W05h08m
19.7
s+
17d
21m
47.5
s(1
73.1
)05h
08m
19.7
s+
17d
21m
47.5
s(8
9.3
)0.1
2(0
.005)
-0.0
1(0
.03)
3.7
5(0
.05)
1.0
4b
CG
CG
468-0
02
E05h
08m
21.2
s+
17d
22m
07.7
s(1
73.1
)05h
08m
21.2
s+
17d
22m
07.7
s(8
9.3
)0.5
4(0
.01)
-0.9
5(0
.04)
10.3
8(0
.19)
1.0
3b
IRA
S05083+
2441
S05h
11m
25.9
s+
24d
45m
18.0
s(1
70.4
)05h
11m
25.9
s+
24d
45m
18.0
s(8
6.6
)0.7
2(0
.01)
-0.1
6(0
.04)
7.9
9(0
.11)
1.1
7N
VII
Zw
031
05h
16m
46.4
s+
79d
40m
12.7
s(1
55.0
)05h
16m
46.3
s+
79d
40m
12.7
s(7
1.3
)0.6
4(0
.01)
-0.2
2(0
.04)
7.3
7(0
.11)
1.2
7N
0IR
AS
05129+
5128
05h
16m
56.0
s+
51d
31m
57.3
s(2
.3)
05h
16m
56.0
s+
51d
31m
57.3
s(-
81.5
)0.5
4(0
.01)
-0.6
1(0
.04)
8.7
5(0
.11)
1.2
7d
IRA
SF
05189-2
524
05h
21m
01.3
s-2
5d
21m
45.6
s(-
2.5
)05h
21m
01.4
s-2
5d
21m
46.1
s(-
86.2
)0.0
3(0
.002)
-0.2
9(0
.02)
5.0
4(0
.01)
0.9
8d
IRA
SF
05187-1
017
05h
21m
06.5
s-1
0d
14m
46.8
s(-
13.7
)05h
21m
06.5
s-1
0d
14m
46.2
s(-
108.7
)0.5
3(0
.03)
-0.6
4(0
.14)
14.9
0(0
.51)
1.0
6N
16 Stierwalt et al.
Sou
rceS
hort-L
ow
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ)
Sca
leM
erger
MS
Nam
e[J
2000]
[ ◦]
[J2000]
[ ◦]
[µm
]F
acto
rS
tage
(HS
T)
IRA
S05223+
1908
05h
25m
16.7
s+
19d
10m
48.0
s(-1
0.1
)05h
25m
16.7
s+
19d
10m
48.0
s(-9
3.8
)<
0.0
1(—
)0.1
2(0
.02)
2.0
0(0
.01)
0.9
9N
MC
G+
08-1
1-0
02
05h
40m
43.7
s+
49d
41m
41.3
s(1
69.6
)05h
40m
43.7
s+
49d
41m
41.3
s(8
5.9
)0.5
6(0
.01)
-0.8
9(0
.03)
9.4
7(0
.08)
1.2
2d
NG
C1961
05h
42m
04.7
s+
69d
22m
43.1
s(1
62.9
)05h
42m
04.7
s+
69d
22m
43.2
s(7
9.2
)0.2
4(0
.01)
0.0
3(0
.09)
4.1
8(0
.05)
1.9
3d
UG
C03351
05h
45m
48.2
s+
58d
42m
03.1
s(1
55.1
)05h
45m
48.1
s+
58d
42m
03.2
s(7
1.4
)0.5
3(0
.01)
-0.6
8(0
.04)
6.8
8(0
.10)
1.0
7a
IRA
S05442+
1732
05h
47m
11.2
s+
17d
33m
46.5
s(-9
.3)
05h
47m
11.2
s+
17d
33m
46.6
s(-9
3.0
)0.6
6(0
.01)
-0.3
8(0
.02)
7.5
2(0
.03)
1.1
6a
IRA
SF
06076-2
139
06h
09m
45.8
s-2
1d
40m
23.9
s(1
66.3
)06h
09m
45.8
s-2
1d
40m
23.8
s(1
10.0
)0.3
3(0
.02)
-1.3
9(0
.09)
7.9
8(0
.10)
—c
UG
C03410
W06h
13m
58.8
s+
80d
28m
35.2
s(1
54.7
)06h
13m
58.8
s+
80d
28m
35.2
s(7
0.8
)0.6
2(0
.01)
0.1
5(0
.04)
3.3
8(0
.06)
1.6
0a
UG
C03410
E06h
14m
30.5
s+
80d
26m
59.9
s(1
54.6
)06h
14m
30.5
s+
80d
26m
59.9
s(7
1.0
)0.6
3(0
.01)
0.1
4(0
.05)
5.1
9(0
.03)
1.7
9a
NG
C2146
06h
18m
37.5
s+
78d
21m
24.3
s(1
7.7
)06h
18m
37.7
s+
78d
21m
25.8
s(-6
2.4
)0.6
7(0
.01)
-0.4
3(0
.02)
9.9
6(0
.01)
2.4
3d
ES
O255-IG
007
W06h
27m
21.7
s-4
7d
10m
36.5
s(-1
28.8
)06h
27m
21.7
s-4
7d
10m
36.4
s(1
47.4
)0.6
2(0
.01)
-0.2
6(0
.02)
8.3
1(0
.03)
—b
3E
SO
255-IG
007
E06h
27m
22.5
s-4
7d
10m
47.6
s(-1
28.8
)06h
27m
22.5
s-4
7d
10m
47.5
s(1
47.4
)0.6
5(0
.02)
0.2
6(0
.02)
8.0
5(0
.04)
—b
3E
SO
255-IG
007
S06h
27m
23.1
s-4
7d
11m
02.9
s(-1
28.8
)06h
27m
23.1
s-4
7d
11m
02.9
s(1
47.4
)0.6
9(0
.02)
-0.1
0(0
.02)
7.2
7(0
.04)
—b
3E
SO
557-G
002
S06h
31m
45.7
s-1
7d
38m
44.8
s(-1
67.6
)06h
31m
45.7
s-1
7d
38m
44.7
s(1
08.7
)0.7
0(0
.07)
0.3
4(0
.06)
6.4
2(0
.64)
1.0
9a
ES
O557-G
002
N06h
31m
47.2
s-1
7d
37m
16.5
s(-1
67.6
)06h
31m
47.2
s-1
7d
37m
16.4
s(1
08.7
)0.6
0(0
.01)
-0.7
3(0
.04)
12.1
8(0
.09)
1.0
4a
UG
C03608
06h
57m
34.4
s+
46d
24m
10.7
s(1
74.4
)06h
57m
34.4
s+
46d
24m
10.7
s(9
0.6
)0.5
3(0
.01)
-0.3
2(0
.03)
7.4
0(0
.07)
1.1
3b
IRA
SF
06592-6
313
06h
59m
40.3
s-6
3d
17m
52.5
s(-1
64.8
)06h
59m
40.3
s-6
3d
17m
52.5
s(1
11.5
)0.4
8(0
.01)
-0.3
1(0
.04)
6.9
8(0
.08)
1.1
0N
AM
0702-6
01
N07h
03m
24.1
s-6
0d
15m
21.8
s(-1
63.8
)07h03m
24.1
s-6
0d
15m
21.8
s(1
12.4
)0.0
4(0
.002)
-0.1
0(0
.02)
3.1
1(0
.01)
1.2
4a
1A
M0702-6
01
S07h
03m
28.5
s-6
0d
16m
43.6
s(-1
63.8
)07h
03m
28.5
s-6
0d
16m
43.6
s(1
12.4
)0.6
8(0
.01)
-0.0
5(0
.03)
7.2
1(0
.72)
1.3
7a
1N
GC
2342
07h
09m
18.1
s+
20d
38m
09.5
s(2
.6)
07h
09m
18.1
s+
20d
38m
09.9
s(9
9.4
)0.6
7(0
.01)
-0.0
6(0
.03)
8.0
7(0
.11)
1.2
8a
NG
C2369
07h
16m
37.9
s-6
2d
20m
36.4
s(5
0.9
)∗07h
16m
37.8
s-6
2d
20m
34.2
s(4
3.2
)∗0.4
8(0
.01)
-0.6
0(0
.02)
5.8
8(0
.02)
1.6
5N
IRA
S07251-0
248
07h
27m
37.6
s-0
2d
54m
54.2
s(-1
70.4
)07h
27m
37.6
s-0
2d
54m
54.2
s(1
05.9
)0.0
9(0
.01)
-2.3
5(0
.14)
13.3
8(0
.12)
1.1
0d
NG
C2388
07h
28m
53.4
s+
33d
49m
08.9
s—
0.5
3(0
.005)
0.0
7(0
.06)
——
aM
CG
+02-2
0-0
03
S07h
35m
41.5
s+
11d
36m
42.0
s(-1
73.9
)07h
35m
41.5
s+
11d
36m
42.0
s(1
02.3
)0.5
8(0
.05)
0.4
7(0
.18)
4.6
2(0
.66)
1.7
4a
MC
G+
02-2
0-0
03
N07h
35m
43.5
s+
11d
42m
34.7
s(-1
73.9
)07h
35m
43.4
s+
11d
42m
34.7
s(1
02.3
)0.1
7(0
.003)
-0.4
9(0
.04)
10.0
8(0
.14)
1.2
6a
IRA
S08355-4
944
08h
37m
01.8
s-4
9d
54m
30.3
s(-1
55.8
)08h
37m
01.8
s-4
9d
54m
30.2
s(1
20.5
)0.1
9(0
.003)
-0.3
2(0
.02)
6.5
9(0
.04)
1.1
6d
3IR
AS
F08339+
6517
—08h
38m
23.2
s+
65d
07m
14.5
s(1
09.0
)—
—7.3
7(0
.05)
—N
NG
C2623
08h
38m
24.1
s+
25d
45m
17.4
s(1
1.9
)08h
38m
24.1
s+
25d
45m
17.2
s(-7
1.8
)0.2
7(0
.01)
-1.1
2(0
.05)
14.6
6(0
.13)
1.0
5d
5E
SO
432-IG
006
W08h
44m
27.2
s-3
1d
41m
50.9
s(-1
55.6
)08h
44m
27.2
s-3
1d
41m
50.8
s(1
20.7
)0.6
4(0
.01)
0.0
2(0
.04)
6.2
3(0
.11)
1.2
9b
ES
O432-IG
006
E08h
44m
28.9
s-3
1d
41m
30.4
s(-1
55.6
)08h
44m
28.9
s-3
1d
41m
30.3
s(1
20.7
)0.4
1(0
.01)
-0.0
1(0
.07)
6.9
1(0
.14)
1.0
5b
ES
O60-IG
016
08h
52m
31.8
s-6
9d
01m
55.8
s(-8
4.5
)08h
52m
31.8
s-6
9d
01m
55.7
s(-1
68.2
)0.1
1(0
.004)
-1.7
6(0
.04)
7.7
1(0
.04)
1.0
9b
3
MIR Properties of Nearby LIRGs 17
Sou
rce
Sh
ort
-Low
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s 9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ
)S
cale
Mer
ger
MS
Nam
e[J
2000]
[◦]
[J2000]
[◦]
[µm
]F
act
or
Sta
ge
(HS
T)
IRA
SF
08572+
3915
09h
00m
25.4
s+
39d
03m
54.6
s(1
9.0
)09h
00m
25.4
s+
39d
03m
55.1
s(-
64.7
)<
0.0
3(—
)-3
.58
(0.0
4)
5.2
4(0
.01)
1.0
1d
3IR
AS
09022-3
615
09h
04m
12.7
s-3
6d
27m
01.6
s(2
3.2
)09h
04m
12.7
s-3
6d
27m
01.7
s(-
60.5
)0.1
4(0
.004)
-0.8
8(0
.03)
7.9
7(0
.05)
1.0
5d
IRA
SF
09111-1
007
W09h
13m
36.5
s-1
0d
19m
30.0
s(-
160.9
)09h
13m
36.5
s-1
0d
19m
29.9
s(1
15.4
)0.4
7(0
.02)
-0.7
3(0
.10)
12.5
4(0
.39)
1.1
3b
IRA
SF
09111-1
007
E09h
13m
38.9
s-1
0d
19m
19.9
s(-
160.9
)09h
13m
38.9
s-1
0d
19m
19.9
s(1
15.4
)0.5
2(0
.03)
-0.1
5(0
.07)
5.9
1(0
.26)
1.3
0b
UG
C04881
W09h
15m
54.7
s+
44d
19m
50.7
s(-
161.0
)09h
15m
54.7
s+
44d
19m
50.7
s(1
15.3
)0.6
1(0
.01)
-0.2
7(0
.04)
9.1
7(0
.31)
1.1
0c
UG
C04881
E09h
15m
55.5
s+
44d
19m
57.2
s(-
161.0
)09h
15m
55.5
s+
44d
19m
57.3
s(1
15.3
)0.4
0(0
.01)
-0.8
1(0
.04)
10.2
2(0
.17)
1.0
1c
UG
C05101
09h
35m
51.6
s+
61d
21m
11.7
s(4
7.4
)09h
35m
51.7
s+
61d
21m
12.0
s(-
36.4
)0.1
3(0
.005)
-0.7
8(0
.05)
7.6
9(0
.05)
0.9
9d
MC
G+
08-1
8-0
13
—09h
36m
37.2
s+
48d
28m
27.9
s(1
19.2
)—
—7.4
8(0
.05)
—a
Arp
303
S09h
46m
20.3
s+
03d02m
44.3
s(-
163.3
)09h
46m
20.3
s+
03d
02m
44.4
s(1
12.9
)0.6
0(0
.02)
0.0
6(0
.04)
6.0
6(0
.11)
2.5
5a
Arp
303
N09h
46m
21.1
s+
03d
04m
15.9
s(-
163.3
)09h
46m
21.1
s+
03d
04m
16.0
s(1
12.9
)0.5
7(0
.06)
0.0
8(0
.09)
4.5
6(0
.10)
1.5
8a
NG
C3110
10h
04m
02.0
s-0
6d
28m
29.5
s(1
61.6
)∗10h
04m
02.2
s-0
6d
28m
31.9
s(6
5.7
)∗0.6
4(0
.01)
0.1
9(0
.03)
5.9
1(0
.04)
2.1
0a
ES
O374-I
G032
10h
06m
04.7
s-3
3d
53m
06.3
s(-
128.3
)10h
06m
04.7
s-3
3d
53m
06.2
s(1
48.0
)0.0
3(0
.002)
-2.7
4(0
.04)
9.3
6(0
.03)
1.1
3d
IRA
SF
10173+
0828
10h
20m
00.2
s+
08d
13m
33.8
s(-
162.9
)10h
20m
00.2
s+
08d
13m
33.6
s(1
13.3
)0.3
5(0
.04)
-1.2
0(0
.12)
35.4
0(1
.38)
1.0
7a
NG
C3221
10h
22m
20.3
s+
21d
34m
22.1
s(-
162.9
)10h
22m
20.3
s+
21d
34m
22.1
s(1
13.3
)0.7
5(0
.01)
-0.1
2(0
.04)
5.9
4(0
.05)
1.4
4N
NG
C3256
10h
27m
51.2
s-4
3d
54m
13.8
s(-
5.5
)10h
27m
51.3
s-4
3d
54m
13.9
s(-
57.4
)0.6
1(0
.01)
-0.2
8(0
.02)
8.1
6(0
.04)
1.3
3d
5E
SO
264-G
036
10h
43m
07.5
s-4
6d
12m
44.3
s(-
111.2
)10h
43m
07.5
s-4
6d
12m
44.3
s(1
65.0
)0.4
4(0
.01)
-0.0
4(0
.02)
5.4
9(0
.03)
1.8
7N
ES
O264-G
057
10h
59m
01.8
s-4
3d
26m
25.8
s(-
137.5
)10h
59m
01.8
s-4
3d
26m
25.8
s(1
38.8
)0.6
0(0
.01)
-0.1
9(0
.04)
7.4
6(0
.10)
1.3
4d
IRA
SF
10565+
2448
10h
59m
18.1
s+
24d
32m
34.9
s(2
5.3
)10h
59m
18.1
s+
24d
32m
35.4
s(-
58.4
)0.5
1(0
.01)
-0.7
5(0
.04)
9.5
1(0
.07)
1.0
8d
2M
CG
+07-2
3-0
19
11h
03m
54.0
s+
40d
51m
00.7
s(-
159.7
)11h
03m
54.0
s+
40d
51m
00.7
s(1
16.6
)0.6
4(0
.01)
-0.5
5(0
.03)
12.4
0(1
.24)
1.1
4d
CG
CG
011-0
76
11h
21m
12.2
s-0
2d
59m
02.4
s(1
64.4
)∗11h
21m
12.3
s-0
2d
59m
03.0
s(1
57.9
)∗0.3
2(0
.02)
-0.4
2(0
.03)
4.3
5(0
.05)
1.3
0a
IRA
SF
11231+
1456
11h
25m
45.1
s+
14d
40m
35.8
s(-
166.8
)11h
25m
45.1
s+
14d
40m
36.4
s(1
17.0
)0.6
0(0
.01)
-0.2
2(0
.03)
8.9
0(0
.20)
0.9
3a
1E
SO
319-G
022
11h
27m
54.1
s-4
1d
36m
52.4
s(-
126.3
)11h
27m
54.1
s-4
1d
36m
52.4
s(1
50.0
)0.4
2(0
.02)
-0.3
0(0
.05)
10.8
1(0
.17)
1.1
1d
NG
C3690
W11h
28m
31.1
s+
58d
33m
41.6
s(1
08.8
)∗11h
28m
31.1
s+
58d
33m
43.6
s(4
4.3
)∗0.1
2(0
.002)
-0.7
7(0
.02)
4.4
8(0
.00)
—c
3N
GC
3690
E11h
28m
33.8
s+
58d
33m
47.0
s(5
1.5
)∗11h
28m
33.7
s+
58d
33m
48.3
s(4
4.3
)∗0.3
8(0
.003)
-1.6
5(0
.02)
12.1
2(0
.01)
1.4
4c
3E
SO
320-G
030
11h
53m
11.6
s-3
9d
07m
47.3
s(1
66.3
)∗11h
53m
11.6
s-3
9d
07m
45.6
s(1
58.2
)∗0.5
8(0
.01)
-0.2
2(0
.02)
13.2
4(0
.05)
1.4
4N
ES
O440-I
G058
N12h
06m
51.7
s-3
1d
56m
46.4
s(-
152.0
)12h
06m
51.7
s-3
1d
56m
46.3
s(1
24.3
)0.5
6(0
.02)
0.3
7(0
.04)
9.8
0(0
.98)
—b
ES
O440-I
G058
S12h
06m
51.9
s-3
1d
56m
59.2
s(-
152.0
)12h
06m
51.9
s-3
1d
56m
59.1
s(1
24.3
)0.6
6(0
.01)
-0.4
5(0
.03)
7.5
6(0
.06)
1.2
1b
IRA
SF
12112+
0305
12h
13m
46.0
s+
02d
48m
40.8
s(-
161.5
)12h
13m
46.0
s+
02d
48m
40.6
s(1
14.8
)0.3
0(0
.03)
-1.2
4(0
.14)
16.6
5(0
.34)
1.1
3d
4E
SO
267-G
030
W12h
13m
52.3
s-4
7d
16m
25.9
s(-
132.3
)12h
13m
52.3
s-4
7d
16m
25.8
s(1
44.0
)0.6
8(0
.01)
-0.0
8(0
.04)
7.3
9(0
.10)
1.1
5a
NG
C4194
12h
14m
09.6
s+
54d
31m
34.3
s(1
79.7
)12h
14m
09.5
s+
54d
31m
33.8
s(9
6.0
)0.5
5(0
.005)
-0.2
9(0
.02)
7.6
5(0
.05)
1.3
7d
18 Stierwalt et al.
Sou
rceS
hort-L
ow
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ)
Sca
leM
erger
MS
Nam
e[J
2000]
[ ◦]
[J2000]
[ ◦]
[µm
]F
acto
rS
tage
(HS
T)
ES
O267-G
030
E12h
14m
12.8
s-4
7d
13m
43.0
s(-1
32.4
)12h
14m
12.8
s-4
7d
13m
42.9
s(1
43.9
)0.5
0(0
.01)
-0.0
1(0
.03)
4.8
6(0
.06)
1.6
1a
IRA
S12116-5
615
12h
14m
22.1
s-5
6d
32m
32.9
s(-1
32.4
)12h
14m
22.1
s-5
6d
32m
32.8
s(1
43.9
)0.3
6(0
.01)
-0.8
5(0
.03)
7.9
3(0
.07)
1.1
1N
0IR
AS
F12224-0
624
12h
25m
03.9
s-0
6d
40m
52.2
s(1
7.5
)12h25m
03.9
s-0
6d
40m
52.1
s(-6
6.3
)0.0
7(0
.02)
-2.1
2(0
.15)
28.3
4(1
.46)
0.9
5N
NG
C4418
12h
26m
54.6
s-0
0d
52m
40.0
s(1
8.9
)12h
26m
54.6
s-0
0d
52m
40.1
s(-6
4.8
)<
0.0
2(—
)-3
.51
(0.0
9)
7.8
3(0
.01)
1.0
4N
UG
C08058
12h
56m
14.3
s+
56d
52m
25.4
s(8
0.3
)12h
56m
14.4
s+
56d
52m
24.7
s(-3
.4)
0.0
1(0
.001)
-0.4
8(0
.02)
3.6
7(0
.01)
1.0
2d
NG
C4922
13h
01m
25.3
s+
29d
18m
50.0
s—
0.1
6(0
.003)
-0.6
0(0
.24)
——
cC
GC
G043-0
99
13h
01m
50.3
s+
04d
20m
00.1
s(-1
64.9
)13h
01m
50.3
s+
04d
20m
00.2
s(1
11.4
)0.5
5(0
.01)
-0.8
1(0
.03)
9.1
2(0
.17)
1.1
4d
MC
G-0
2-3
3-0
98
W13h
02m
19.7
s-1
5d
46m
04.0
s(-1
60.9
)13h
02m
19.7
s-1
5d
46m
03.9
s(1
15.3
)0.5
5(0
.01)
-0.0
4(0
.03)
5.7
7(0
.07)
1.1
5b
MC
G-0
2-3
3-0
98
E13h
02m
20.4
s-1
5d
45m
59.4
s(-1
60.9
)13h
02m
20.4
s-1
5d
45m
59.3
s(1
15.3
)0.7
0(0
.02)
0.0
4(0
.05)
8.4
7(0
.21)
1.2
9b
ES
O507-G
070
13h
02m
52.4
s-2
3d
55m
18.3
s(-1
53.1
)13h02m
52.4
s-2
3d
55m
18.2
s(1
23.2
)0.5
6(0
.01)
-1.2
4(0
.10)
13.5
8(0
.19)
1.1
0d
IRA
S13052-5
711
13h
08m
18.7
s-5
7d
27m
29.9
s(-1
44.6
)13h
08m
18.7
s-5
7d
27m
29.9
s(1
31.7
)0.6
1(0
.01)
-0.5
1(0
.03)
12.0
9(0
.21)
1.1
2a
IC0860
13h
15m
03.5
s+
24d
37m
08.0
s(-1
77.8
)13h
15m
03.5
s+
24d
37m
08.1
s(9
8.4
)0.4
3(0
.01)
-0.9
8(0
.11)
33.1
5(0
.29)
1.1
4N
IRA
S13120-5
453
13h
15m
06.5
s-5
5d
09m
23.6
s(-1
37.2
)13h
15m
06.5
s-5
5d
09m
23.8
s(1
39.1
)0.4
5(0
.01)
-0.9
1(0
.03)
12.5
4(0
.07)
1.2
6d
5V
V250a
W13h
15m
30.7
s+
62d
07m
45.7
s(-1
37.5
)13h
15m
30.7
s+
62d
07m
45.7
s(1
38.8
)0.7
6(0
.03)
-0.2
3(0
.11)
8.0
9(0
.33)
1.3
5b
2V
V250a
E13h
15m
35.0
s+
62d
07m
29.1
s(-1
37.5
)13h
15m
35.0
s+
62d
07m
29.1
s(1
38.8
)0.6
3(0
.01)
-0.6
7(0
.03)
7.6
5(0
.05)
1.0
3b
2U
GC
08387
13h
20m
35.4
s+
34d
08m
22.1
s(-1
69.5
)13h
20m
35.4
s+
34d
08m
22.2
s(1
05.6
)0.6
2(0
.01)
-1.0
1(0
.03)
10.8
0(0
.10)
1.0
7d
4N
GC
5104
13h
21m
23.1
s+
00d
20m
32.6
s(-1
67.4
)13h
21m
23.2
s+
00d
20m
33.2
s(1
13.7
)0.5
1(0
.01)
-0.4
7(0
.04)
6.6
7(0
.11)
1.2
1N
MC
G-0
3-3
4-0
64
13h
22m
24.5
s-1
6d
43m
42.7
s(-1
59.5
)13h
22m
24.5
s-1
6d
43m
42.6
s(1
16.8
)<
0.0
1(—
)-0
.18
(0.0
2)
2.1
3(0
.00)
0.9
6a
NG
C5135
13h
25m
44.1
s-2
9d
50m
00.7
s(1
5.0
)13h
25m
44.2
s-2
9d
50m
00.4
s(-6
8.7
)0.4
9(0
.01)
-0.2
4(0
.02)
5.7
8(0
.03)
1.5
3N
ES
O173-G
015
13h
27m
23.8
s-5
7d
29m
21.7
s(-1
48.7
)13h27m
23.8
s-5
7d
29m
21.6
s(1
27.5
)0.5
3(0
.01)
-1.3
1(0
.08)
15.0
4(0
.07)
—N
IC4280
13h
32m
53.4
s-2
4d
12m
25.3
s(-1
57.6
)13h
32m
53.4
s-2
4d
12m
25.2
s(1
18.6
)0.5
9(0
.01)
0.1
3(0
.04)
5.2
4(0
.09)
1.5
6N
NG
C5256
13h
38m
17.7
s+
48d
16m
32.9
s(-1
62.4
)13h
38m
17.6
s+
48d
16m
33.9
s(1
13.9
)0.4
4(0
.02)
-0.4
7(0
.03)
6.4
1(0
.03)
—b
3A
rp240
W13h
39m
53.0
s+
00d
50m
25.3
s(1
9.1
)13h
39m
53.0
s+
00d
50m
25.3
s(-6
4.6
)0.6
3(0
.01)
-0.0
1(0
.03)
7.1
8(0
.19)
1.6
6b
2A
rp240
E13h
39m
57.7
s+
00d
49m
51.0
s(1
9.1
)13h
39m
57.7
s+
00d
49m
51.0
s(-6
4.6
)0.5
4(0
.01)
0.1
2(0
.03)
6.3
1(0
.19)
1.6
9b
UG
C08696
13h
44m
42.2
s+
55d
53m
13.2
s(9
3.5
)13h
44m
42.3
s+
55d
53m
12.6
s(9
.8)
0.1
2(0
.01)
-1.3
7(0
.05)
12.3
6(0
.07)
1.0
6d
4U
GC
08739
13h
49m
13.9
s+
35d
15m
26.6
s(-1
69.7
)13h
49m
13.9
s+
35d
15m
26.6
s(1
06.5
)0.5
1(0
.01)
-0.5
9(0
.03)
6.7
4(0
.12)
2.1
4N
ES
O221-IG
010
13h
50m
56.9
s-4
9d
03m
19.2
s(-1
53.3
)13h
50m
56.9
s-4
9d
03m
19.1
s(1
23.0
)0.6
9(0
.01)
0.0
3(0
.03)
7.2
6(0
.08)
1.4
8N
NG
C5331
S13h
52m
16.2
s+
02d
06m
05.5
s(-1
71.0
)13h
52m
16.2
s+
02d
06m
05.5
s(1
05.2
)0.6
1(0
.01)
-0.4
3(0
.03)
7.0
6(0
.10)
1.1
9c
3N
GC
5331
N13h
52m
16.5
s+
02d
06m
31.3
s(-1
71.0
)13h
52m
16.4
s+
02d
06m
31.3
s(1
05.2
)0.6
0(0
.01)
0.1
3(0
.03)
5.2
4(0
.24)
1.1
1c
3A
rp84
N13h
58m
33.6
s+
37d
27m
13.2
s(-1
78.0
)13h
58m
33.6
s+
37d
27m
13.2
s(9
8.2
)0.6
2(0
.01)
-0.0
8(0
.03)
6.8
4(0
.03)
1.0
9c
MIR Properties of Nearby LIRGs 19
Sou
rce
Sh
ort
-Low
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s 9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ
)S
cale
Mer
ger
MS
Nam
e[J
2000]
[◦]
[J2000]
[◦]
[µm
]F
act
or
Sta
ge
(HS
T)
Arp
84
S13h
58m
37.9
s+
37d
25m
28.2
s(-
178.0
)13h
58m
37.9
s+
37d
25m
28.2
s(9
8.2
)0.1
7(0
.02)
0.5
2(0
.07)
3.8
2(0
.24)
2.1
0c
CG
CG
247-0
20
14h
19m
43.3
s+
49d
14m
11.5
s(-
152.2
)14h
19m
43.3
s+
49d
14m
11.6
s(1
15.2
)0.5
6(0
.01)
-0.2
0(0
.03)
7.6
4(0
.10)
1.1
3N
NG
C5653
14h
30m
10.4
s+
31d
12m
56.1
s(1
72.7
)14h
30m
10.4
s+
31d
12m
56.1
s(8
9.0
)0.5
4(0
.01)
0.2
5(0
.03)
7.3
5(0
.04)
—N
IRA
SF
14348-1
447
14h
37m
38.4
s-1
5d
00m
24.0
s(-
167.2
)14h
37m
38.3
s-1
5d
00m
24.6
s(1
09.1
)0.2
5(0
.01)
-1.3
6(0
.16)
16.7
6(0
.36)
1.1
4d
4IR
AS
F14378-3
651
14h
40m
59.0
s-3
7d
04m
33.1
s(-
160.3
)14h
40m
58.9
s-3
7d
04m
33.0
s(1
16.0
)0.3
9(0
.03)
-1.1
4(0
.16)
15.7
1(0
.30)
1.0
8d
6N
GC
5734
N14h
45m
09.0
s-2
0d
52m
13.2
s(-
167.1
)14h
45m
09.0
s-2
0d
52m
13.2
s(1
09.1
)0.4
7(0
.01)
0.1
2(0
.03)
5.0
1(0
.14)
1.6
6a
NG
C5734
S14h
45m
11.0
s-2
0d
54m
48.7
s(-
167.1
)14h
45m
11.0
s-2
0d
54m
48.5
s(1
09.1
)0.4
9(0
.01)
-0.0
4(0
.04)
5.0
7(0
.08)
2.1
5a
VV
340a
S14h
57m
00.3
s+
24d
36m
24.2
s(1
77.8
)14h
57m
00.3
s+
24d
36m
24.3
s(9
4.1
)0.5
8(0
.02)
0.3
3(0
.04)
4.8
2(0
.31)
1.3
7b
1V
V340a
N14h
57m
00.7
s+
24d
37m
05.4
s(1
77.8
)14h
57m
00.7
s+
24d
37m
05.5
s(9
4.1
)0.5
8(0
.01)
-0.6
3(0
.03)
6.2
1(0
.10)
0.8
2b
1C
GC
G049-0
57
15h
13m
13.1
s+
07d
13m
33.1
s(1
55.9
)∗15h
13m
13.0
s+
07d
13m
35.2
s(5
9.8
)∗0.5
1(0
.04)
-0.8
3(0
.03)
31.4
0(0
.39)
1.0
5N
VV
705
15h
18m
06.4
s+
42d
44m
36.6
s(-
145.5
)—
0.7
5(0
.06)
0.3
2(0
.06)
——
bE
SO
099-G
004
15h
24m
58.0
s-6
3d
07m
29.2
s(-
169.3
)15h
24m
58.0
s-6
3d
07m
29.1
s(1
06.9
)0.5
3(0
.01)
-0.7
8(0
.04)
7.7
4(0
.06)
1.0
4d
3IR
AS
F15250+
3608
15h
26m
59.4
s+
35d
58m
37.7
s(1
70.1
)15h
26m
59.4
s+
35d
58m
37.2
s(8
6.3
)0.0
3(0
.01)
-2.6
9(0
.07)
10.5
2(0
.03)
0.9
7d
5N
GC
5936
15h
30m
00.8
s+
12d
59m
22.3
s(-
172.2
)15h
30m
00.8
s+
12d
59m
22.4
s(1
04.0
)0.6
2(0
.01)
-0.1
3(0
.03)
6.4
1(0
.07)
1.2
5N
Arp
220
15h
34m
57.3
s+
23d
30m
11.7
s(1
78.0
)15h
34m
57.2
s+
23d
30m
11.1
s(9
4.2
)0.1
7(0
.004)
-2.2
6(0
.06)
20.3
8(1
.67)
1.0
8d
4N
GC
5990
15h
46m
16.4
s+
02d
24m
55.7
s(-
171.3
)15h
46m
16.4
s+
02d
24m
55.8
s(1
04.9
)0.1
5(0
.002)
-0.1
1(0
.03)
4.7
4(0
.02)
1.2
2a
NG
C6052
16h
05m
13.1
s+
20d
32m
35.6
s(5
9.0
)∗16h
05m
12.9
s+
20d
32m
35.5
s(5
1.7
)∗0.6
9(0
.03)
-0.0
6(0
.03)
6.6
3(0
.04)
3.0
8c
NG
C6090
16h
11m
40.2
s+
52d
27m
24.9
s(2
6.8
)16h
11m
40.3
s+
52d
27m
24.7
s(-
57.0
)0.7
3(0
.02)
-0.0
4(0
.03)
7.5
4(0
.03)
—c
4IR
AS
F16164-0
746
16h
19m
11.8
s-0
7d
54m
02.7
s(-
177.8
)16h
19m
11.8
s-0
7d
54m
02.7
s(1
02.1
)0.6
1(0
.01)
-1.1
8(0
.07)
11.5
8(0
.20)
1.0
3d
5C
GC
G052-0
37
16h
30m
56.5
s+
04d
04m
58.5
s(1
6.1
)16h
30m
56.5
s+
04d
04m
58.8
s(1
01.2
)0.6
2(0
.01)
-0.2
1(0
.02)
7.0
7(0
.09)
1.1
6N
NG
C6156
16h
34m
52.5
s-6
0d
37m
07.5
s(-
179.8
)16h
34m
52.5
s-6
0d
37m
07.5
s(9
6.4
)0.3
7(0
.01)
0.4
7(0
.02)
5.8
9(0
.02)
1.2
3N
ES
O069-I
G006
16h
38m
11.8
s-6
8d
26m
08.0
s(1
78.6
)16h
38m
11.8
s-6
8d
26m
07.9
s(9
4.8
)0.6
4(0
.01)
-0.4
0(0
.04)
7.9
1(0
.10)
1.1
7b
2IR
AS
F16399-0
937
16h
42m
40.1
s-0
9d
43m
13.5
s(-
176.4
)16h
42m
40.1
s-0
9d
43m
13.4
s(9
9.9
)0.4
3(0
.01)
-1.1
2(0
.04)
9.0
9(0
.09)
1.1
4d
3E
SO
453-G
005
N16h
47m
29.4
s-2
9d
19m
06.8
s(-
175.6
)16h
47m
29.4
s-2
9d
19m
06.7
s(1
00.7
)0.7
4(0
.07)
0.4
7(0
.05)
5.2
1(0
.14)
1.5
1N
ES
O453-G
005
S16h
47m
31.1
s-2
9d
21m
21.6
s(-
175.6
)16h
47m
31.1
s-2
9d
21m
21.5
s(1
00.6
)0.4
2(0
.01)
-0.4
7(0
.09)
27.1
1(2
.71)
1.2
2N
NG
C6240
16h
52m
58.9
s+
02d
24m
03.7
s(-
177.4
)16h
52m
58.9
s+
02d
24m
03.0
s(9
8.9
)0.3
5(0
.01)
-0.9
2(0
.07)
7.7
2(0
.04)
1.0
5d
4IR
AS
F16516-0
948
16h
54m
23.9
s-0
9d
53m
20.6
s(-
177.9
)16h
54m
23.9
s-0
9d
53m
20.5
s(9
8.4
)0.6
9(0
.01)
0.1
8(0
.03)
7.0
2(0
.15)
1.6
7d
NG
C6286
N16h
58m
24.0
s+
58d
57m
21.4
s(-
117.4
)16h
58m
24.0
s+
58d
57m
21.9
s(1
16.3
)0.6
6(0
.02)
0.0
8(0
.03)
6.8
1(0
.07)
1.1
4b
NG
C6286
S16h
58m
31.3
s+
58d
56m
10.7
s(2
7.8
)16h
58m
31.7
s+
58d
56m
13.5
s(1
16.3
)0.5
9(0
.01)
-0.4
0(0
.03)
5.9
7(0
.04)
0.9
1b
IRA
SF
17132+
5313
—17h
14m
20.2
s+
53d
10m
30.4
s(-
102.2
)—
—9.6
7(0
.97)
—b
20 Stierwalt et al.
Sou
rceS
hort-L
ow
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ)
Sca
leM
erger
MS
Nam
e[J
2000]
[ ◦]
[J2000]
[ ◦]
[µm
]F
acto
rS
tage
(HS
T)
IRA
SF
17138-1
017
17h
16m
35.6
s-1
0d
20m
37.9
s(1
73.8
)17h
16m
36.0
s-1
0d
20m
41.2
s(1
.2)∗
0.6
8(0
.01)
-0.3
7(0
.04)
7.1
7(1
.51)
4.1
2d
6IR
AS
F17207-0
014
17h
23m
22.0
s-0
0d
17m
00.8
s(1
73.2
)17h
23m
22.0
s-0
0d
17m
01.0
s(8
9.5
)0.3
1(0
.01)
-1.2
6(0
.07)
26.3
9(0
.24)
1.2
2d
5E
SO
138-G
027
17h
26m
43.4
s-5
9d
55m
54.8
s(-1
77.1
)17h
26m
43.3
s-5
9d
55m
54.7
s(9
9.1
)0.5
2(0
.01)
-0.3
5(0
.06)
8.1
3(0
.03)
1.1
4N
UG
C11041
17h
54m
51.9
s+
34d
46m
34.0
s(-1
4.4
)17h
54m
51.9
s+
34d
46m
34.0
s(-9
8.2
)0.5
8(0
.01)
0.0
7(0
.03)
5.2
7(0
.04)
2.2
6N
CG
CG
141-0
34
17h
56m
56.6
s+
24d
01m
01.8
s(-1
1.9
)17h
56m
56.6
s+
24d
01m
01.8
s(-9
5.6
)0.4
8(0
.01)
-0.6
4(0
.06)
9.3
5(0
.16)
1.1
8N
IRA
S17578-0
400
W18h
00m
24.3
s-0
4d
01m
04.2
s(1
71.6
)18h
00m
24.3
s-0
4d
01m
04.1
s(8
7.9
)0.6
2(0
.02)
0.1
6(0
.09)
8.5
6(0
.25)
2.2
8b
IRA
S17578-0
400
N18h
00m
31.8
s-0
4d
00m
53.8
s(1
71.6
)18h
00m
31.8
s-0
4d
00m
53.7
s(8
7.9
)0.6
8(0
.01)
-0.6
7(0
.05)
21.1
8(0
.24)
1.4
5b
IRA
S17578-0
400
S18h
00m
34.1
s-0
4d
01m
44.3
s(1
71.6
)18h
00m
34.1
s-0
4d
01m
44.2
s(8
7.9
)0.7
8(0
.01)
0.1
5(0
.07)
6.3
8(0
.21)
1.8
3a
IRA
S18090+
0130
W18h
11m
33.4
s+
01d
31m
42.3
s(1
69.3
)18h
11m
33.4
s+
01d
31m
42.4
s(8
5.5
)0.5
2(0
.03)
-0.7
2(0
.10)
8.0
4(0
.26)
1.1
9b
IRA
S18090+
0130
E18h
11m
38.4
s+
01d
31m
40.2
s(1
69.3
)18h
11m
38.4
s+
01d
31m
40.3
s(8
5.5
)0.6
1(0
.01)
-0.2
8(0
.04)
7.1
6(0
.06)
1.2
2b
2N
GC
6621
18h
12m
55.2
s+
68d
21m
48.4
s(2
1.6
)∗18h
12m
54.8
s+
68d
21m
48.7
s(5
.2)∗
0.5
6(0
.01)
-0.1
6(0
.02)
5.8
3(0
.01)
1.2
6b
IC4687
18h
13m
39.7
s-5
7d
43m
30.5
s(1
3.6
)∗18h
13m
40.2
s-5
7d
43m
33.5
s(2
.1)∗
0.7
3(0
.02)
0.1
2(0
.02)
6.5
0(0
.02)
1.5
6b
CG
CG
142-0
34
W18h16m
33.8
s+
22d
06m
38.9
s(1
72.9
)18h
16m
33.8
s+
22d
06m
39.0
s(8
9.1
)0.4
8(0
.01)
-0.2
4(0
.03)
5.6
2(0
.21)
1.0
3a
CG
CG
142-0
34
E18h
16m
40.7
s+
22d
06m
46.4
s(1
72.9
)18h
16m
40.7
s+
22d
06m
46.5
s(8
9.1
)0.5
1(0
.01)
-0.4
8(0
.03)
7.3
4(0
.11)
1.9
5a
IRA
SF
18293-3
413
18h
32m
41.1
s-3
4d
11m
27.1
s(-8
.8)
18h
32m
41.1
s-3
4d
11m
27.1
s(-9
2.5
)0.6
3(0
.01)
-0.5
1(0
.02)
7.6
6(0
.05)
1.3
8c
1N
GC
6670
W18h
33m
34.3
s+
59d
53m
17.9
s(-7
.3)
18h33m
34.3
s+
59d
53m
17.9
s(-9
1.0
)0.6
3(0
.01)
-0.2
2(0
.03)
8.8
2(0
.11)
1.8
5b
2N
GC
6670
E18h
33m
37.8
s+
59d
53m
22.8
s(-7
.3)
18h
33m
37.8
s+
59d
53m
22.8
s(-9
1.0
)0.6
1(0
.01)
-0.3
4(0
.03)
8.7
8(0
.10)
1.2
6b
2IC
4734
18h
38m
25.8
s-5
7d
29m
25.4
s(1
67.4
)18h
38m
25.8
s-5
7d
29m
25.3
s(8
3.7
)0.5
1(0
.01)
-0.6
0(0
.04)
8.2
6(0
.09)
1.3
5N
NG
C6701
18h
43m
12.5
s+
60d
39m
11.9
s(-6
.0)
18h
43m
12.5
s+
60d
39m
11.9
s(-8
9.8
)0.5
5(0
.01)
-0.1
5(0
.09)
7.1
0(0
.07)
1.2
7N
VV
414
W19h
10m
53.9
s+
73d
24m
36.1
s(0
.6)
19h
10m
53.9
s+
73d
24m
36.1
s(-8
3.2
)0.6
4(0
.01)
0.1
0(0
.03)
7.2
4(0
.06)
1.4
1c
2V
V414
E19h
11m
04.3
s+
73d
25m
32.6
s(0
.6)
19h
11m
04.3
s+
73d
25m
32.6
s(-8
3.1
)0.2
9(0
.01)
-0.0
8(0
.02)
5.4
6(0
.02)
1.0
8c
2E
SO
593-IG
008
19h
14m
31.2
s-2
1d
19m
06.4
s(-1
3.2
)19h
14m
31.2
s-2
1d
19m
06.3
s(-9
6.9
)0.5
6(0
.01)
-0.5
9(0
.03)
8.9
2(0
.12)
1.3
8d
4IR
AS
F19297-0
406
19h
32m
22.3
s-0
4d
00m
00.2
s(1
56.3
)19h
32m
22.3
s-0
4d
00m
00.2
s(7
2.6
)0.3
0(0
.02)
-1.0
5(0
.13)
15.0
7(0
.25)
1.1
6d
4IR
AS
19542+
1110
19h
56m
35.8
s+
11d
19m
05.4
s(-6
.4)
19h
56m
35.8
s+
11d
19m
05.4
s(-9
0.1
)0.2
9(0
.02)
-0.7
4(0
.08)
14.5
3(0
.31)
1.0
7N
0E
SO
339-G
011
19h
57m
37.6
s-3
7d
56m
08.4
s(-2
2.0
)19h
57m
37.6
s-3
7d
56m
08.4
s(-1
05.8
)0.2
7(0
.01)
-0.3
1(0
.03)
4.6
4(0
.04)
1.2
2N
NG
C6907
20h
25m
06.5
s-2
4d
48m
32.6
s(-2
2.2
)20h
25m
06.5
s-2
4d
48m
32.5
s(-1
05.9
)0.5
7(0
.01)
0.1
0(0
.03)
6.6
7(0
.04)
1.6
2N
MC
G+
04-4
8-0
02
20h
28m
35.1
s+
25d
44m
00.2
s(2
.8)
20h
28m
35.1
s+
25d
44m
00.2
s(-8
0.9
)0.5
7(0
.01)
-0.4
7(0
.03)
5.2
2(0
.05)
1.7
3a
NG
C6926
20h
33m
06.1
s-0
2d
01m
38.8
s(-1
2.0
)20h
33m
06.1
s-0
2d
01m
38.7
s(-9
5.7
)0.3
7(0
.01)
-0.4
9(0
.03)
5.0
7(0
.05)
1.4
5d
IRA
S20351+
2521
20h
37m
17.7
s+
25d
31m
39.1
s(3
.8)
20h
37m
17.7
s+
25d
31m
39.1
s(-7
9.9
)0.5
7(0
.01)
-0.2
4(0
.04)
7.5
0(0
.10)
1.6
8N
0C
GC
G448-0
20
W20h57m
24.0
s+
17d
07m
35.1
s(-1
1.9
)20h
57m
24.0
s+
17d
07m
35.2
s(-9
5.6
)0.4
8(0
.01)
-0.4
2(0
.02)
9.1
4(0
.04)
—c
3
MIR Properties of Nearby LIRGs 21
Sou
rce
Sh
ort
-Low
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s 9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ
)S
cale
Mer
ger
MS
Nam
e[J
2000]
[◦]
[J2000]
[◦]
[µm
]F
act
or
Sta
ge
(HS
T)
CG
CG
448-0
20
E20h
57m
24.3
s+
17d
07m
39.1
s(-
11.9
)20h
57m
24.3
s+
17d
07m
39.2
s(-
95.6
)0.2
7(0
.01)
-0.9
2(0
.03)
9.8
2(0
.04)
—c
3IR
AS
20551-4
250
20h
58m
26.8
s-4
2d
39m
01.7
s(1
62.1
)20h
58m
26.7
s-4
2d
39m
02.8
s(7
8.4
)0.1
0(0
.01)
-2.5
2(0
.10)
7.5
9(0
.02)
1.0
4d
5E
SO
286-G
035
21h
04m
11.1
s-4
3d
35m
34.4
s(-
27.5
)21h
04m
11.1
s-4
3d
35m
34.4
s(-
111.2
)0.6
9(0
.01)
-0.2
4(0
.03)
7.0
2(0
.09)
1.4
3a
IRA
S21101+
5810
21h
11m
29.3
s+
58d
23m
07.6
s(1
0.5
)21h
11m
29.3
s+
58d
23m
07.6
s(-
73.2
)0.5
5(0
.02)
-0.8
7(0
.07)
11.0
6(0
.15)
1.0
4c
2E
SO
343-I
G013
S21h
36m
10.5
s-3
8d
32m
42.4
s(-
31.9
)21h
36m
10.5
s-3
8d
32m
42.4
s(-
115.6
)0.6
1(0
.01)
-0.0
9(0
.03)
9.2
1(0
.18)
—c
ES
O343-I
G013
N21h
36m
10.9
s-3
8d
32m
32.6
s(-
1.9
)21h
36m
10.9
s-3
8d
32m
32.6
s(-
115.6
)0.4
7(0
.01)
-0.4
8(0
.02)
6.7
1(0
.07)
—c
NG
C7130
21h
48m
19.6
s-3
4d
57m
01.9
s(1
54.1
)21h
48m
19.5
s-3
4d
57m
02.1
s(7
0.4
)0.3
0(0
.01)
-0.2
7(0
.03)
5.6
7(0
.03)
1.4
2N
ES
O467-G
027
22h
14m
39.9
s-2
7d
27m
51.4
s(-
36.7
)22h
14m
39.9
s-2
7d
27m
51.3
s(-
120.4
)0.6
2(0
.01)
0.2
9(0
.02)
5.4
8(0
.09)
2.2
4N
IC5179
22h
16m
09.0
s-3
6d
50m
38.1
s(1
21.5
)∗22h
16m
09.3
s-3
6d
50m
33.8
s(1
15.9
)∗0.6
3(0
.01)
0.0
7(0
.02)
5.4
2(0
.02)
2.4
3N
ES
O602-G
025
22h
31m
25.5
s-1
9d
02m
04.0
s(-
31.4
)22h
31m
25.4
s-1
9d
02m
04.0
s(-
117.1
)0.4
5(0
.01)
-0.6
6(0
.04)
6.2
3(0
.08)
1.1
7N
UG
C12150
22h
41m
12.2
s+
34d
14m
56.9
s(-
20.1
)22h
41m
12.2
s+
34d
14m
56.8
s(-
98.7
)0.5
3(0
.01)
-0.4
2(0
.02)
8.1
4(0
.09)
1.2
7N
ES
O239-I
G002
22h
49m
39.8
s-4
8d
50m
58.4
s(-
48.3
)22h
49m
39.8
s-4
8d
50m
58.4
s(-
132.0
)0.4
5(0
.02)
-0.4
9(0
.04)
10.3
5(0
.12)
1.0
8d
5IR
AS
F22491-1
808
22h
51m
49.4
s-1
7d
52m
24.5
s(1
55.2
)22h
51m
49.2
s-1
7d
52m
24.8
s(7
1.5
)0.4
8(0
.02)
-1.0
4(0
.13)
17.6
3(0
.33)
1.1
4d
4N
GC
7469
23h
03m
15.6
s+
08d
52m
26.2
s(-
29.7
)23h
03m
15.6
s+
08d
52m
27.3
s(-
113.4
)0.2
3(0
.002)
0.0
6(0
.02)
4.8
1(0
.03)
1.1
2a
2C
GC
G453-0
62
23h
04m
56.5
s+
19d
33m
07.6
s(-
24.9
)23h
04m
56.6
s+
19d33m
07.8
s(-
103.6
)0.5
8(0
.02)
-0.4
6(0
.04)
12.8
3(0
.10)
1.5
0N
ES
O148-I
G002
23h
15m
47.0
s-5
9d
03m
17.0
s(1
36.3
)23h
15m
47.0
s-5
9d
03m
18.4
s(5
2.6
)0.3
1(0
.01)
-0.6
6(0
.03)
6.4
9(0
.05)
1.0
3c
4IC
5298
23h
16m
00.7
s+
25d
33m
24.4
s(-
19.5
)23h
16m
00.7
s+
25d
33m
24.5
s(-
103.3
)0.1
2(0
.004)
-0.3
7(0
.02)
7.4
1(0
.02)
1.0
1N
0N
GC
7552
23h
16m
10.6
s-4
2d
35m
03.8
s(1
12.9
)∗23h
16m
10.6
s-4
2d
35m
05.8
s(1
07.8
)∗0.5
6(0
.01)
-0.2
1(0
.02)
6.6
2(0
.01)
1.7
2N
NG
C7591
23h
18m
16.3
s+
06d
35m
08.7
s(-
27.4
)23h
18m
16.2
s+
06d
35m
09.2
s(-
109.7
)0.4
8(0
.01)
-0.3
7(0
.05)
7.9
6(0
.13)
1.2
1N
NG
C7592
W23h
18m
21.7
s-0
4d
24m
57.6
s(1
19.1
)∗23h
18m
21.5
s-0
4d
24m
54.2
s(1
12.9
)∗0.3
0(0
.01)
-1.0
8(0
.03)
5.1
3(0
.02)
1.1
0b
NG
C7592
E23h
18m
22.7
s-0
4d
24m
57.8
s(1
19.1
)∗23h
18m
22.8
s-0
4d
25m
02.3
s(1
12.9
)∗0.6
9(0
.01)
0.1
1(0
.02)
8.3
8(0
.07)
1.2
0b
ES
O077-I
G014
W23h
21m
03.7
s-6
9d
13m
00.9
s(-
55.8
)23h
21m
03.7
s-6
9d
13m
00.9
s(-
139.5
)0.6
3(0
.01)
-0.5
9(0
.04)
11.8
4(0
.17)
—b
2E
SO
077-I
G014
E23h
21m
05.4
s-6
9d
12m
47.2
s(-
55.8
)23h
21m
05.4
s-6
9d
12m
47.2
s(-
139.5
)0.4
9(0
.01)
-0.6
1(0
.03)
12.5
4(0
.12)
—b
2N
GC
7674
23h
27m
56.7
s+
08d
46m
44.5
s(1
16.5
)∗23h
27m
56.6
s+
08d
46m
41.8
s(2
0.5
)∗0.0
2(0
.01)
-0.1
3(0
.02)
2.5
2(0
.02)
1.1
3a
2N
GC
7679
23h
28m
46.6
s+
03d
30m
41.7
s(-
27.4
)23h
28m
46.6
s+
03d
30m
41.7
s(-
111.1
)0.6
4(0
.01)
0.3
4(0
.02)
5.7
8(0
.06)
1.4
1a
IRA
SF
23365+
3604
23h
39m
01.3
s+
36d
21m
10.2
s(-
35.5
)23h
39m
01.4
s+
36d
21m
11.3
s(-
119.2
)0.4
1(0
.02)
-1.4
1(0
.17)
10.0
4(0
.11)
1.8
9d
5M
CG
-01-6
0-0
22
—23h
42m
00.7
s-0
3d
36m
54.7
s(-
114.0
)—
—7.2
4(0
.13)
—a
IRA
S23436+
5257
23h
46m
05.4
s+
53d
14m
01.3
s(-
3.9
)23h
46m
05.4
s+
53d
14m
01.3
s(-
87.7
)0.3
7(0
.01)
-0.2
2(0
.03)
7.0
0(0
.06)
1.2
4c
4A
rp86
S23h
46m
58.5
s+
29d
27m
31.6
s(-
19.8
)23h
46m
58.5
s+
29d
27m
31.8
s(-
103.5
)0.7
2(0
.01)
0.1
2(0
.02)
6.1
4(0
.11)
1.6
1b
Arp
86
N23h
47m
04.8
s+
29d
28m
59.6
s(-
19.7
)23h
47m
04.8
s+
29d
28m
59.8
s(-
103.5
)0.3
2(0
.01)
0.1
4(0
.04)
6.7
2(0
.18)
1.5
3b
22 Stierwalt et al.
Sou
rceS
hort-L
ow
RA
/D
EC
(PA
)L
on
g-L
ow
RA
/D
EC
(PA
)6.2µm
EQ
W(σ
)s9.7µm
(σ)
Fν[3
0µm
]/Fν[1
5µm
](σ)
Sca
leM
erger
MS
Nam
e[J
2000]
[ ◦]
[J2000]
[ ◦]
[µm
]F
acto
rS
tage
(HS
T)
NG
C7771
W23h
51m
04.0
s+
20d
09m
02.0
s(-1
9.8
)23h
51m
04.0
s+
20d
09m
02.0
s(-1
03.6
)0.3
9(0
.01)
0.2
7(0
.06)
6.2
6(0
.11)
1.3
4N
NG
C7771
S23h
51m
22.5
s+
20d
05m
47.0
s(-1
9.8
)23h
51m
22.5
s+
20d
05m
47.0
s(-1
03.6
)0.3
6(0
.01)
-0.2
0(0
.04)
4.4
2(0
.05)
2.1
1c
NG
C7771
N23h
51m
24.9
s+
20d
06m
43.0
s(-1
9.8
)23h
51m
24.9
s+
20d
06m
43.1
s(-1
03.6
)0.5
2(0
.01)
-0.2
4(0
.03)
8.4
3(0
.04)
1.9
5a
MR
K0331
23h
51m
26.7
s+
20d
35m
10.1
s(-1
9.6
)23h
51m
26.7
s+
20d
35m
10.3
s(-1
03.3
)0.6
3(0
.01)
-0.3
5(0
.03)
9.4
0(0
.05)
1.1
9a
1M
IRS
pectra
lP
ara
meters
of
the
GO
AL
SS
am
ple.
Colu
mn
(1):
Sou
rceN
am
e,C
olu
mn
s(2
)-(5):
the
centra
lrig
ht
ascen
sion
,d
eclinatio
n,
an
dp
ositio
nan
gle
of
the
field
of
view
for
the
SL
an
dL
Lob
servatio
ns
(for
starin
gm
od
ed
ata
:R
AF
OV
,D
EC
FO
V,
&P
AF
OV
from
the
hea
ders
with
ap
oin
ting
accu
racy
with
in1′′;
for
map
pin
gm
od
ed
ata
:ca
lcula
tedfro
mth
efo
ur
corn
ersof
the
extra
ction
ap
erture
used
inC
UB
ISM
),C
olu
mn
(6):
the
equ
ivalen
tw
idth
of
the
6.2µ
mP
AH
featu
rein
µm
,C
olu
mn
(7):
the
ap
paren
td
epth
of
the
9.7µ
msilica
teab
sorp
tion
featu
re,C
olu
mn
(8):
the
MIR
slop
eca
lcula
tedu
sing
Fν
at
15
an
d30µ
m,
Colu
mn
(9):
the
SL
-to-L
Lsca
lefa
ctor,
Colu
mn
(10):
the
merg
ersta
ge
(N=
non
merg
er,a
=p
re-merg
er,b
=ea
rlysta
ge
merg
er,c
=m
id-sta
ge
merg
er,an
dd
=la
testa
ge
merg
er,see
Sectio
n2.5
for
deta
ils),an
dC
olu
mn
(11):
merg
ersta
ge
as
deriv
edfro
mth
eh
igh
resolu
tion
HS
Td
ata
(0=
non
merg
er,1
=p
re-merg
er,2
=on
goin
gm
erger
with
separa
ble
pro
gen
itor
gala
xies,
3=
on
goin
gm
erger
with
pro
gen
itors
sharin
ga
com
mon
envelo
pe,
4=
on
goin
gm
erger
with
dou
ble
nu
cleip
lus
tidal
tail,
5=
post-m
erger
with
single
nu
cleus
plu
sp
rom
inen
tta
il,an
d6
=p
ost-m
erger
with
single
nu
cleus
with
distu
rbed
morp
holo
gy,
as
describ
edin
Haan
etal.
(2011)).
∗D
ata
was
taken
inm
ap
pin
gm
od
e,an
dso
the
PA
was
user-selected
.