Extragalactic abstracts - IRSA - California Institute of Technology

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Spitzer_Approved_Extragalactic Mar 25, 10 16:24 Page 431/742 Spitzer Space Telescope − #20371 We propose to study why most supermassive black holes in the local universe appear to be X−ray faint or quiescent. Possible explanations are that: the accretion power is carried out by a jet; or, the nuclei are obscured by dust; or, accretion occurs at very low radiative efficiency (ADAF models); or, most of the infalling gas ends up forming stars instead of being accreted by the black hole. Spitzer observations will give us the key to complete our study of the broad−band spectral energy distribution for a sample of X−ray−faint SMBH nuclei in elliptical galaxies. We shall determine how much of the total energy is really radiated by their nuclei, and test those alternative scenarios quantitatively. Principal Investigator: Giuseppina Fabbiano Institution: Harvard−Smithsonian Center for Astrophysics Technical Contact: Roberto Soria, Harvard−CfA30 Co−Investigators: Roberto Soria, Harvard−Smithsonian Center for Astrophysics Martin Elvis, Harvard−Smithsonian Center for Astrophysics Silvia Pellegrini, Dipartimento di Astronomia − Universita’ di Bologn Alessandro Baldi, Harvard−Smithsonian Center for Astrophysics Science Category: IracMap MipsPhot Hours Approved: 0.0 Abstract: Spitzer_Approved_Extragalactic Printed_by_SSC Mar 25, 10 16:24 Page 432/742 Spitzer Space Telescope − General Observer Proposal #30402 Two Extreme IR−weak Quasars at z~6: Probing Dust Evolution Principal Investigator: Xiaohui Fan Institution: The University of Arizona Technical Contact: Xiaohui Fan, The University of Arizona Co−Investigators: Dean Hines, University of Arizona Linhua Jiang, University of Arizona Lei Hao, Cornell University Gordon Richards, Johns Hopkins University Michael Strauss, Princeton University Nadia Zakamska, Princeton University Science Category: AGN/quasars/radio galaxies Observing Modes: IracMap IrsMap IrsPeakupImage MipsPhot Hours Approved: 21.1 Abstract: We propose to carry out deep Spitzer observations of two z~6 quasars with unusual IR properties to constrain the properties of dust in their environments. Most of the high−redshift (z>4.5) quasars we have observed in our GO−1 and GTO programs have rest−frame near to mid−IR spectral energy distributions similar to those of low−redshift quasars, suggesting very similar dust properties, and indicating that most dust tori form in short timescales at high redshift. However, two objects stand out as highly unusual: SDSS J1411+1217,(z=5.93) has an IR SED consistent with a pure power−law, with no IR excess due to hot dust (T > 1000 K). SDSS J0005−0006 (z=5.85) is completely undetected in our GO−1 24 micron MIPS observation, indicating an IR deficit; its SED is consistent with a pure disk model without a dust torus. Such dust−deficient AGN have not been found at either high or low redshift; the IR/optical flux ratios of these two sources are lower than those of all known type I objects at low redshift with Spitzer photometry. Their IR properties could be due to a complete lack of a dust torus at early epochs, or moderate obscuration in the mid−IR. We will obtain deep Spitzer photometry at 8, 16 and 24 micron for J0005−0006, aiming to detect or put stringent upper limit on its hot dust emission. We will carry out deep photometry at 16 micron and low−resolution IRS spectroscopy for the brighter J1411+1217 in order to constrain dust models. These new observations will shed light on the possible evolution of dust properties in the earliest luminous quasars. Thursday March 25, 2010 xgal_covers.txt 216/371
Spitzer_Approved_Extragalactic Mar 25, 10 16:24 Page 433/742 Spitzer Space Telescope − General Observer Proposal #3198 Infrared Spectral Energy Distributions of the Most Distant Quasars Principal Investigator: Xiaohui Fan Institution: The University of Arizona Technical Contact: Xiaohui Fan, The University of Arizona Co−Investigators: Frank Bertoldi, MPIfR William N. Brandt, PSU Chris L. Carilli, NRAO Pierre Cox, IAS, Paris Dean Hines, SSI Emeric Le Floch, Arizona Gordon T. Richards, Princeton George Rieke, Arizona Donald P. Schneider, PSU Michael A. Strauss, Princeton Marianne Vestergaard, Arizona Fabian Walter, NRAO Science Category: AGN/quasars/radio galaxies Observing Modes: IracMap MipsPhot Hours Approved: 15.0 Abstract: We propose to obtain high S/N Spitzer photometry of a flux−limited sample of thirteen luminous quasars at 5.7 < z < 6.4 selected from the Sloan Digital Sky Survey. They are the thirteen most distant quasars known to date, near the end of the cosmic reionization epoch. The Spitzer observations will be carried out in all the IRAC bands, the MIPS 24 micron band, and for the brightest sources, in the MIPS 70 micron band. These observations will provide the first high S/N Spitzer measurement of luminous objects at z>6, and establish the basic infrared characteristics of the most distant quasars. The Spitzer observations sample the rest−frame near to mid−IR, a wavelength range that has never been probed before at this redshift, where the radiation begins to be dominated by hot dust in the quasar environment and where the SED might peak. High quality X−ray, optical/near−IR, sub−millimeter and radio observations of this sample have either been acquired or planned. Combined with measurements in other wavelengths, the Spitzer data will allow us to measure the bolometric luminosity of z~6 quasars and to estimate the accretion rate and efficiency of the earliest billion solar mass black holes in the universe. Comparing with low−redshift samples, including the Spitzer GTO sample at 0 < z < 5, we will study the evolution of quasar SEDs to the first billion years of cosmic history, constraining physical models of the highest−redshift quasars. Finally, combining with sub−millimeter and radio molecular gas observations, we will study dust properties in the quasar environment and the AGN/starburst connection in the earliest massive galaxies. Spitzer_Approved_Extragalactic Printed_by_SSC Mar 25, 10 16:24 Page 434/742 Spitzer Space Telescope − General Observer Proposal #3221 Lineless Quasars at High−Redshift: BL Lacs or A New Class of Unbeamed Quasars? Principal Investigator: Xiaohui Fan Institution: The University of Arizona Technical Contact: Xiaohui Fan, The University of Arizona Co−Investigators: Scott F. Anderson, Washington Wiliam N. Brandt, PSU J. Serena Kim, Arizona Donald P. Schneider, PSU Michael A. Strauss, Princeton Science Category: AGN/quasars/radio galaxies Observing Modes: IracMap MipsPhot Hours Approved: 4.5 Abstract: The Sloan Digital Sky Survey (SDSS) has recently discovered a class of high−redshift quasars with no or extremely weak optical emission lines. Their redshifts are determined by the presence of strong Lyman break and Lyman Limit Systems. Their nature remains unknown: they could be analogs of BL Lac objects at high redshift, a new type of unbeamed quasar whose broad emission−line region is very weak or absent, or a combination of both. The proto−type object, SDSS J1532−0039 (z=4.6), lacks other signatures of a typical BL Lac object: it has no detectable radio or X−ray emission and is not strongly polarized or variable in the optical. Other objects in the sample show a variety of radio and X−ray properties. We propose to obtain Spitzer IRAC and MIPS 24 micron photometry of four lineless quasars at z = 4 − 4.6, two of which are radio/X−ray quiet, and the other two are radio/X−ray loud. The Spitzer photometry will probe the spectral region where there is a dramatic contrast between beamed synchrotron emission in BL Lac objects and thermal dust emission in unbeamed quasars: we expect a factor of 5 difference in Spitzer fluxes between the two cases. It will reveal the nature of the IR emission mechanism, and unambiguously determine whether these lineless quasars are beamed sources similar to BL Lac objects, or a new type of unbeamed quasar. Thursday March 25, 2010 xgal_covers.txt 217/371
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Extragalactic abstracts - IRSA - California Institute of Technology

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