The SEDs of Interacting Galaxies
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Transcript of The SEDs of Interacting Galaxies
The SEDs of Interacting Galaxies
Lauranne LanzNicola Brassington, Andreas Zezas, Howard A. Smith, Matthew L. N. Ashby,
Elisabete da Cunha, Christopher Klein, Patrik Jonsson, Chris HaywardLars Hernquist, Giovanni Fazio
Harvard-Smithsonian Center for [email protected]
NGC 520:NUV, 3.6 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Outline
• What is Spitzer Interacting Galaxy Survey (SIGS)?
• SED shapes• SED fitting• sSFR comparisons• Trends with interaction stage
N3226-N32273.6 µm, 4.5 µm, & 8 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Sample Selection• Keel-Kennicutt (Keel et al. 1985) “complete” and
“Arp” samples:– Selected based on association likelihood– Require |Δv|< 600 km s-1 to remove non-associated pairs
• Imposed distance constraint cz < 4000 km s-1
• Resulting sample: 111 galaxies in 50 systems
NGC 2976:NUV, 3.6 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Observations
• Complete Spitzer coverage: – IRAC, MIPS, and nuclear IRS spectra
• Almost complete GALEX coverage• Some Herschel coverage• Ancillary data– WISE coverage– Some Chandra/XMM coverage– Hα fluxes
M51NUV, IRAC 3.6 µm, & SPIRE 250 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Sample Selection and Observation Set Benefits
• Not morphologically selected: large range of interaction parameters
• Not infrared selected: less active systems included• Not based on optical line diagnostics• UV and IR coverage gives complete SFR
NGC 470 & NGC 474:FUV, 3.6 and 4.5 µm, & 8.0 µm
NGC 520:NUV, 3.6 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Example: M51 and NGC 3430/3424
SPIRE 250 µm
IRAC3.6 µm, 4.5 µm, 8 µm
GALEX FUV NUV
2MASSJ, H, Ks
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Photometry
• S-Extractor used to determine NUV and 3.6 µm apertures
SPIRE 250 µm
IRAC3.6 µm, 4.5 µm, 8 µm
GALEX FUV NUV
2MASSJ, H, Ks
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Photometry
• S-Extractor used to determine NUV and 3.6 µm apertures
• Fluxes determined in larger aperture in all bands• Uncertainty: Calibration and Poisson
SPIRE 250 µm
IRAC3.6 µm, 4.5 µm, 8 µm
GALEX FUV NUV
2MASSJ, H, Ks
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
SED shapes
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
M51 A
NGC 3424 NGC 3430
M51 B
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Two blackbodies + β=1.5 graybody
4367 K 356.2 K 28.6 K 4058 K 357.1 K 25.8 K
3572 K 303.5 K 29.2 K 3307 K 339.5 K 25.2 K
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
Log(
νL ν /
L)
M51 A
NGC 3424 NGC 3430
M51 B
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
MagPhys SED-fitting Code
• Optical stellar from Bruzual & Charlot 2003 and infrared dust from da Cunha, Charlot, & Elbaz 2008 spectral libraries
• Energy absorbed in UV/optical is re-emitted in IR• No AGN contribution considered• Likelihood distributions constructed for model
parameters to determine best fit SED
Elisabete da Cunha’s talk this afternoon
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit SEDsLo
g( λ
L λ / L
)
Log(
λL λ
/ L)
sSFR
TwarmTcold
sSFR
TwarmTcold
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit SEDsLo
g( λ
L λ / L
)
Log(
λL λ
/ L)
sSFR
TwarmTcold
sSFR
TwarmTcold
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Fit comparisonsFIR β=1.5 gray-body temperature falls between SED-fitted warm and cold temperatures
The integrated 8-1000 µm 3-component fit agrees well with the dust luminosity determined from fitting the SED.
Log( LDust, SED / L) F
rac.
Diff
eren
ce
Log
( L8-
1000
µm, 3p
art /
L)
TWarm
TCold
TGraybody / K
T SED
/ K
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Log(sSFR/yr-1) SED Fitting
Log(
sSFR
/yr-1
) Pre
scrip
tion
Comparison of Specific Star Formation Rates
M51A
N 3430
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Trends with Interaction Stage
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Summary• SIGS will provide a sample of interacting
galaxies from first pass to coalescence with a range of interaction parameters.
IC 1801 and NGC 935NUV, 3.6 and 4.5 µm, & 8.0 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Summary• With the first 10 groups with SPIRE data, we:– find a range of SED shapes, especially in the ratio
of MIR to optical/UV.– measured sSFR and temperatures using the
MagPhys (da Cunha et al. 2008) SED-fitting code.– find an increase in warm component temperature
with interaction stage, but no significant change in sSFR.
M81:NUV, 8.0 µm, & 250 µm
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011
Thank you for the attention and stay tuned for more:• 40 more interacting groups
• Nuclear activity• Comparison with simulated systems
N3448 – U6016:FUV, 3.6 µm, 4.5 µm, & 8 µm
M101:NUV, 3.6 µm, & 8 µm
Cox et al. 2006
L. Lanz, Harvard-CFA, SED2011 Sept. 6, 2011