IR SIR Spectral Diagnostics of z=2 pectral Diagnostics of z=2 Dust Obscured Galaxies (DOGs)Dust Obscured Galaxies (DOGs)

Jason Melbourne (Caltech)B.T. Soifer, Lee Armus, Keith Matthews, Vandana Desai, Arjun Dey, Shane

Bussmann

Melbourne et al. 2008

DOGs are Defined by Very Red DOGs are Defined by Very Red Optical to Mid-IR Colors Optical to Mid-IR Colors

• R-[24] > 14 (Vega mag)

• F[24]/F[R] > 1000

• Significant amounts of warm dust.

• Total IR energy densities great than ULIRGs.

Dey et al. 2008

Over 2000 DOGs Identified in the Over 2000 DOGs Identified in the NOAO Deep Wide Field Survey of NOAO Deep Wide Field Survey of

BootesBootes

• 10 square degrees• BRI ground based imaging

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

• Spitzer IRAC imaging • Spitzer MIPS imaging

The Redshift Distribution of DOGs The Redshift Distribution of DOGs is Centered About z=2is Centered About z=2

• Median redshift of z = 1.99

z = 0.5

Dey et al. 2008

Spectral Energy Distributions Vary Spectral Energy Distributions Vary

with 24 micron Fluxwith 24 micron Flux

• Brighter DOGs tend to show power-law SEDs.

• Fainter DOGs tend to show a “bump” in the observed mid-IR.

Dey et al. 2008

IRS Spectra of Power-Law DOGs IRS Spectra of Power-Law DOGs Suggest AGN ActivitySuggest AGN Activity

Weedman et al. 2005

IRS Spectra of “Bump” DOGs IRS Spectra of “Bump” DOGs Suggest Star FormationSuggest Star Formation

Desai et al. 2009

TripleSpec: 5 Orders in the Near-TripleSpec: 5 Orders in the Near-IR, Including J, H, and K in One IR, Including J, H, and K in One

Spectrum Spectrum

Spectra of Spectra of Power-LawPower-Law DOGs DOGs Reveal Reveal Broad HBroad H

Melbourne et al. in prep

H [nm]

z Line width [km/s]

2.282 2.477 1370

2.144 2.266 2350

1.761 1.684 2760

1.510 1.300 1550

1.260 0.919 1190

H

1

2

3

4

5

Spectra of Spectra of “Bump”“Bump” DOGs DOGs Reveal Reveal Narrow HNarrow H

Melbourne et al. in prep

H [nm]

z Line width [km/s]

2.235 2.405 320

1.550 1.365 420

H

1

2

Broad Ha from AGN dominates, Broad Ha from AGN dominates, but narrow Ha suggests star but narrow Ha suggests star

formation formation

Broad H

Narrow H

OSIRIS Sample is AGN DominatedOSIRIS Sample is AGN Dominated

These look different These look different

SummarySummary

• A simple optical to mid-IR color selection identifies extreme z=2 ULIRGs.

• These Dust Obscured Galaxies (DOGs) may evolve into massive the ellipticals of today.

• DOGs are powered by a combination of SF and AGN activity.

• OSIRIS observations pinpoint the location of the AGN and constrain SFR.

Spectra of Spectra of Power-LawPower-Law DOGs DOGs Reveal Reveal Broad HBroad H

Observed Wavelength (m)

Cou

nts

1.5 1.6 1.7 1.8