Extragalactic abstracts - IRSA - California Institute of Technology
Extragalactic abstracts - IRSA - California Institute of Technology
Extragalactic abstracts - IRSA - California Institute of Technology
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Spitzer_Approved_<strong>Extragalactic</strong><br />
Mar 25, 10 16:24 Page 433/742<br />
Spitzer Space Telescope − General Observer Proposal #3198<br />
Infrared Spectral Energy Distributions <strong>of</strong> the Most Distant Quasars<br />
Principal Investigator: Xiaohui Fan<br />
Institution: The University <strong>of</strong> Arizona<br />
Technical Contact: Xiaohui Fan, The University <strong>of</strong> Arizona<br />
Co−Investigators:<br />
Frank Bertoldi, MPIfR<br />
William N. Brandt, PSU<br />
Chris L. Carilli, NRAO<br />
Pierre Cox, IAS, Paris<br />
Dean Hines, SSI<br />
Emeric Le Floch, Arizona<br />
Gordon T. Richards, Princeton<br />
George Rieke, Arizona<br />
Donald P. Schneider, PSU<br />
Michael A. Strauss, Princeton<br />
Marianne Vestergaard, Arizona<br />
Fabian Walter, NRAO<br />
Science Category: AGN/quasars/radio galaxies<br />
Observing Modes: IracMap MipsPhot<br />
Hours Approved: 15.0<br />
Abstract:<br />
We propose to obtain high S/N Spitzer photometry <strong>of</strong> a flux−limited sample <strong>of</strong><br />
thirteen luminous quasars at 5.7 < z < 6.4 selected from the Sloan Digital Sky<br />
Survey. They are the thirteen most distant quasars known to date, near the end<br />
<strong>of</strong> the cosmic reionization epoch. The Spitzer observations will be carried out<br />
in all the IRAC bands, the MIPS 24 micron band, and for the brightest sources,<br />
in the MIPS 70 micron band. These observations will provide the first high S/N<br />
Spitzer measurement <strong>of</strong> luminous objects at z>6, and establish the basic infrared<br />
characteristics <strong>of</strong> the most distant quasars. The Spitzer observations sample the<br />
rest−frame near to mid−IR, a wavelength range that has never been probed before<br />
at this redshift, where the radiation begins to be dominated by hot dust in the<br />
quasar environment and where the SED might peak. High quality X−ray,<br />
optical/near−IR, sub−millimeter and radio observations <strong>of</strong> this sample have<br />
either been acquired or planned. Combined with measurements in other<br />
wavelengths, the Spitzer data will allow us to measure the bolometric luminosity<br />
<strong>of</strong> z~6 quasars and to estimate the accretion rate and efficiency <strong>of</strong> the earliest<br />
billion solar mass black holes in the universe. Comparing with low−redshift<br />
samples, including the Spitzer GTO sample at 0 < z < 5, we will study the<br />
evolution <strong>of</strong> quasar SEDs to the first billion years <strong>of</strong> cosmic history,<br />
constraining physical models <strong>of</strong> the highest−redshift quasars. Finally, combining<br />
with sub−millimeter and radio molecular gas observations, we will study dust<br />
properties in the quasar environment and the AGN/starburst connection in the<br />
earliest massive galaxies.<br />
Spitzer_Approved_<strong>Extragalactic</strong><br />
Printed_by_SSC<br />
Mar 25, 10 16:24 Page 434/742<br />
Spitzer Space Telescope − General Observer Proposal #3221<br />
Lineless Quasars at High−Redshift: BL Lacs or A New Class <strong>of</strong> Unbeamed Quasars?<br />
Principal Investigator: Xiaohui Fan<br />
Institution: The University <strong>of</strong> Arizona<br />
Technical Contact: Xiaohui Fan, The University <strong>of</strong> Arizona<br />
Co−Investigators:<br />
Scott F. Anderson, Washington<br />
Wiliam N. Brandt, PSU<br />
J. Serena Kim, Arizona<br />
Donald P. Schneider, PSU<br />
Michael A. Strauss, Princeton<br />
Science Category: AGN/quasars/radio galaxies<br />
Observing Modes: IracMap MipsPhot<br />
Hours Approved: 4.5<br />
Abstract:<br />
The Sloan Digital Sky Survey (SDSS) has recently discovered a class <strong>of</strong><br />
high−redshift quasars with no or extremely weak optical emission lines. Their<br />
redshifts are determined by the presence <strong>of</strong> strong Lyman break and Lyman Limit<br />
Systems. Their nature remains unknown: they could be analogs <strong>of</strong> BL Lac objects<br />
at high redshift, a new type <strong>of</strong> unbeamed quasar whose broad emission−line region<br />
is very weak or absent, or a combination <strong>of</strong> both. The proto−type object, SDSS<br />
J1532−0039 (z=4.6), lacks other signatures <strong>of</strong> a typical BL Lac object: it has no<br />
detectable radio or X−ray emission and is not strongly polarized or variable in<br />
the optical. Other objects in the sample show a variety <strong>of</strong> radio and X−ray<br />
properties. We propose to obtain Spitzer IRAC and MIPS 24 micron photometry <strong>of</strong><br />
four lineless quasars at z = 4 − 4.6, two <strong>of</strong> which are radio/X−ray quiet, and<br />
the other two are radio/X−ray loud. The Spitzer photometry will probe the<br />
spectral region where there is a dramatic contrast between beamed synchrotron<br />
emission in BL Lac objects and thermal dust emission in unbeamed quasars: we<br />
expect a factor <strong>of</strong> 5 difference in Spitzer fluxes between the two cases. It will<br />
reveal the nature <strong>of</strong> the IR emission mechanism, and unambiguously determine<br />
whether these lineless quasars are beamed sources similar to BL Lac objects, or<br />
a new type <strong>of</strong> unbeamed quasar.<br />
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