16 micron Imaging in the GOODS fields with the Spitzer IRS

Harry Teplitz(Spitzer Science Center)

The Usual SuspectsNorth (IRS GTO + SV data)L. Armus, R. Chary, J. Colbert (SSC)V. Charmandaris(Crete)D. Weedman,J. Houck & IRS IT (Cornell)

GOODS SouthR. Chary,J. ColbertD. Stern(SSC/JPL)M. Dickinson (NOAO)D. ElbazD. Marcillac(CEA)

Why 16m?

• PAH emission: • 17.1 at z~0• 11.3 to z~0.5 • 6.2,7.7,8.6 at z~1

• Silicate absorption:• 9.7 m detected

at z~0.7• avoid siliacate

at z~1.5M51 (Smith et al.)

Why 16m?

• Enhances Spitzer SED coverage• factor of 3 -gap between IRAC & MIPS• MIR slope, much fainter than spectroscopy

IRS “Peak-up” Imaging New Cycle 2 AOT provides science

quality (RAW mode) imaging Blue and Red are observed in together Share common WCS SL spectra obtained in parallel

300+ hours requested in Cycle 2 75 Jy, 3, in 120 s 54”x81” 1.8”/pixel < 2% distortion FWHM (16mm) = 2 pix

Depths achievable with PUI

• IRS lowres: 0.4-1 mJy ULIRGs at z~1

• PUI: 0.025-0.1 mJy SB at z~1

“CHEAP” Imaging• No PUI AOT in Cycle 1• Offset positioning of

commanded spectra provides RAW-mode data

• Spectra AOT includes 18” nod, resulting in uneven coverage map

Pilot Study: GTO 16 m in GOODS-N

• Images centered on ISO or SCUBA sources (Charmandaris et al. 2004).

• 35 arcmin2, 20 have 2 pt /pix

• 153 sources; 0.03 -- 0.8Jy.• 24 sources in ISOCAM

survey (Aussel et al. 1999) • All sources detected in

GOODS MIPS data

Comparison with ISO

Possibleconfusion

HDF-North

GOODS South• Data obtained in Feb ‘05

• Some DCEs lost to latent imaging

• Nested Survey• 150 sq. arcmin, 2 min

per pix, 0.09 mJy 3• 10 sq. arcmin, 8 min

per pix, 0.04 mJy 3• 515 sources detected,

matched to IRAC Chan-1• No MIPS comparison

until summer 2005

Number Counts• Roughly in agreement with

ISOCAM results • Some confused ISOCAM

sources are resolved by Spitzer

• The HDF-N pilot study is not an unbiased survey

• Marleau et al. (2004) find 24 m number counts peak at fainter flux than 15 m counts

• difference b/w 15 and 24 m counts is not the result of confusion of ISOCAM sources or systematic differences between the observatories

Redshifts• Redshifts from e.g.

• TKRS, Hawaii, Cohen et al., in North, • VIRMOS, etc. in the South

• Known redshift spikes in North are seen at z~0.45 and z~0.9. • 16m imaging may pick out members of the z~0.45 spike

16mAll (norm)

North South

Chandra sources• NORTH: 73 X-ray sources in

the 2 Msec Chandra catalog within the pilot study area.• 35 have 16m counterparts • ~30% of Spitzer 16m

sources have X-ray counterparts.

• SOUTH: 197 X-ray sources from the 1 Msec catalog• 73 have 16m counterparts • ~15% of Spitzer 16m

sources have X-ray counterparts.

Chandra Sources • Fadda et al. (2003) find 25%

of ISO sources with have (1 Msec) Chandra counterparts. • ~1/3 clearly “AGN

dominated”• Spitzer 16 m is lower at

the 1 Msec level• HB-detection

• 1/3 in N; 2/3 in S• Indicative of more SF at

fainter X-ray fluxes• IR/X shows HB sources

likely have significant AGN contrib.

North

Extrapolating to LIR

• Spitzer template spectra (Armus; Spoon; Brandl 2005)• North: use slope of 16-24• (H0=70, -flat )

North South

LIRGs and ULIRGs• We detect LIRGs and

ULIRGs at z>1• More ULIRGs at higher z• These objects dominate

faint source counts (Chary et al. 2004; Lagache et

al. 2004)• At z~1.5, 16 m is

preferable to 24

Flux Ratio

• Charmandaris et al. (2004) suggest that 16/24 m ratio separates AGN from starbursts

Evidence of PAH

Conclusions

• Spitzer 16 m imaging detects evidence for PAH emission at z~1

• Depths achievable in short integrations can observe LIRGs at z>1

• SEDs extend what is possible with spectroscopy

• easily detects AGN• consistent with ISO