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Extragalactic abstracts - IRSA - California Institute of Technology

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Spitzer_Approved_<strong>Extragalactic</strong><br />

Mar 25, 10 16:24 Page 677/742<br />

Spitzer Space Telescope − Guaranteed Time Observer Proposal #50323<br />

IR spectra, star formation rates, and metallicities in submillimeter galaxies<br />

Principal Investigator: George Rieke<br />

Institution: The University <strong>of</strong> Arizona<br />

Technical Contact: Benjamin Weiner, Steward Observatory, U. Arizona<br />

Co−Investigators:<br />

Benjamin Weiner, Steward Observatory<br />

Eiichi Egami, Steward Observatory<br />

Delphine Marcillac, Steward Observatory<br />

Casey Papovich, Steward Observatory<br />

Christopher Willmer, Steward Observatory<br />

Jane Rigby, Carnegie Observatories<br />

Almudena Alonso−Herrero, Instituto de Estructura de la Materia<br />

Chad Engelbracht, Steward Observatory<br />

Science Category: ULIRGS/LIRGS/HLIRGS<br />

Observing Modes: IrsMap MipsPhot<br />

Hours Approved: 8.2<br />

Abstract:<br />

Sub−millimeter continuum observations probe the long−wavelength side <strong>of</strong> far−IR<br />

dust emission from distant galaxies, detecting cold dust and dusty galaxies at<br />

higher redshifts. This makes the sub−mm uniquely sensitive to types <strong>of</strong> dusty<br />

galaxies that are disfavored by shorter−wavelength selection, such as at 24<br />

microns. However, for the same reason, only a relatively small number <strong>of</strong> sub−mm<br />

galaxies have high−quality Spitzer/IRS spectra. We propose to obtain IRS spectra<br />

<strong>of</strong> a carefully selected sample <strong>of</strong> 7 galaxies with sub−mm detections, firm radio<br />

and infrared cross−IDs and positions, sufficient 24 micron flux, and in several<br />

cases, detections at 70 and even 160 microns. These galaxies are in fields with<br />

deep IRAC and MIPS photometry and sensitive multiwavelength coverage from X−ray<br />

to radio. The IRS spectra will determine the restframe mid−IR PAH emission,<br />

silicate absorption, and continuum shape. These features along with far−IR dust<br />

temperatures and multiwavelength data will enable us to construct SEDs for cool,<br />

dusty galaxies at z ~ 0.5−2, and to determine whether the properties <strong>of</strong> such<br />

galaxies are similar to local unusually cool ULIRGs (e.g. Arp 220) or have<br />

evolved with redshift. We are also proposing to take deep IRS exposures to<br />

measure Brackett alpha, [Ne II] and [Ne III] mid−IR lines in 3 <strong>of</strong> the galaxies.<br />

These lines yield measurements <strong>of</strong> star formation rate and metallicity that are<br />

unaffected by extinction. We will test whether IR−luminous galaxies at z~1 are<br />

lower metallicity than local examples, and whether metallicity evolution is<br />

affecting far−IR estimates <strong>of</strong> star formation rate.<br />

Spitzer_Approved_<strong>Extragalactic</strong><br />

Printed_by_SSC<br />

Mar 25, 10 16:24 Page 678/742<br />

Spitzer Space Telescope − Guaranteed Time Observer Proposal #50324<br />

IR spectra, star formation rates, and metallicities in submillimeter galaxies<br />

Principal Investigator: George Rieke<br />

Institution: The University <strong>of</strong> Arizona<br />

Technical Contact: Benjamin Weiner, Steward Observatory, U. Arizona<br />

Co−Investigators:<br />

Benjamin Weiner, Steward Observatory<br />

Eiichi Egami, Steward Observatory<br />

Delphine Marcillac, Steward Observatory<br />

Casey Papovich, Steward Observatory<br />

Christopher Willmer, Steward Observatory<br />

Jane Rigby, Carnegie Observatories<br />

Almudena Alonso−Herrero, Instituto de Estructura de la Materia<br />

Chad Engelbracht, Steward Observatory<br />

Science Category: ULIRGS/LIRGS/HLIRGS<br />

Observing Modes:<br />

Hours Approved: 33.9<br />

Abstract:<br />

Sub−millimeter continuum observations probe the long−wavelength side <strong>of</strong> far−IR<br />

dust emission from distant galaxies, detecting cold dust and dusty galaxies at<br />

higher redshifts. This makes the sub−mm uniquely sensitive to types <strong>of</strong> dusty<br />

galaxies that are disfavored by shorter−wavelength selection, such as at 24<br />

microns. However, for the same reason, only a relatively small number <strong>of</strong> sub−mm<br />

galaxies have high−quality Spitzer/IRS spectra. We propose to obtain IRS spectra<br />

<strong>of</strong> a carefully selected sample <strong>of</strong> 7 galaxies with sub−mm detections, firm radio<br />

and infrared cross−IDs and positions, sufficient 24 micron flux, and in several<br />

cases, detections at 70 and even 160 microns. These galaxies are in fields with<br />

deep IRAC and MIPS photometry and sensitive multiwavelength coverage from X−ray<br />

to radio. The IRS spectra will determine the restframe mid−IR PAH emission,<br />

silicate absorption, and continuum shape. These features along with far−IR dust<br />

temperatures and multiwavelength data will enable us to construct SEDs for cool,<br />

dusty galaxies at z ~ 0.5−2, and to determine whether the properties <strong>of</strong> such<br />

galaxies are similar to local unusually cool ULIRGs (e.g. Arp 220) or have<br />

evolved with redshift. We are also proposing to take deep IRS exposures to<br />

measure Brackett alpha, [Ne II] and [Ne III] mid−IR lines in 3 <strong>of</strong> the galaxies.<br />

These lines yield measurements <strong>of</strong> star formation rate and metallicity that are<br />

unaffected by extinction. We will test whether IR−luminous galaxies at z~1 are<br />

lower metallicity than local examples, and whether metallicity evolution is<br />

affecting far−IR estimates <strong>of</strong> star formation rate. This is part 2 <strong>of</strong> program<br />

50323.<br />

Thursday March 25, 2010 xgal_covers.txt<br />

339/371

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