The Fifth Data Release of the Sloan Digital Sky Survey, J. K. Adelman-McCarthy, 2007, ApJS, 172, 634 (Other) Black hole masses and enrichment of z~6 SDSS quasars, J. D. Kurk, F. Walter, X. Fan et al., 2007. ApJ, 669, 32 (Extragalactic) Detection of 1.6x10^10 M_sun of Molecula Gas in the Host Galaxy of the z = 5.77 SDSS Quasar J0927+2001, Carilli, C. L., et al., 2007, ApJ, 666, L9 (extragalactic) Gemini Near-Infrared Spectroscopy of Luminous z~6 Quasars: Chemical Abundances, Black Holes Masses, and MgII Absorptions, L. Jiang, X. Fan, M. Vestergaard, J. D. Kurk, F. Walter, B. C. Kelly, and M. A. Strauss, 2007, AJ, 134, 1150 (extragalactic) Evidence for a z<8 Origin of the Source Subtracted Near Infrared Background, R. I. Thompson, D. Eisenstein, X. Fan, M. Rieke, R. C. Kennicutt, 2007, ApJ, 666, 658 (extragalactic) Millimeter and Radio Observations of z~6 Quasars, Wang, R. et al., 2007, AJ, 134, 617 (extraglactic) The Sloan Digital Sky Survey Quasar Catalog. IV. Fifth Data Release, D. P. Schneider et al., 2007, AJ, 134, 102 (extragalactic) Clustering of High Redshift z>2.9 Quasars from the Sloan Digital Sky Survey, Shen, Y., et al. 2007, AJ, 133, 2222 (extragalactic) Constraints on the Cosmic Near Infrared Background Excess from NICMOS Deep Field Observations, Thompson, R. I., Eisenstein, D., Fan, X., Rieke, M., & Kennicutt, R. C., 2007, ApJ, 657, 669 (extragalactic) The Radio-Loud Fraction of Quasars is a Strong Function of Redshift and Optical Luminosity, L. Jiang, X. Fan et al., 2007, ApJ, 656, 680 (extragalactic) Physical parameters of two very cool T dwarfs, D. Saumon, M.S. Marley, S.K. Leggett, T.R. Geballe, D. Stephens, D.A. Golimowski, M.C. Cushing, X. Fan, J.T. Rayner, K. Lodders, R.S. Freedman, 2007, ApJ, 656, 1136 (Stellar/Galactic) 3.6-7.9 micron Photometry of L and T Dwarfs ad the Prevalence of Vertical Mixing in their Atmospheres, S. K. Leggett, D. Saumon, M. S. Marley, T. R. Geballe, D. A. Golimowski, D. Stephens, X. Fan, 2007, ApJ, 655, 1079 (Stellar/Galactic)
X. Fan, with graduate student L. Jiang, continue to collaborate
with J. Annis, H. Lin (FNAL), M. Strauss (Princeton), G. T. Richards (Drexel), and
the SDSS quasar group to carry out surveys of distant quasars.
During this year, our effort has been focused on using the deep equatorial
stripe data to extend the luminosity function of quasars at $z\sim 6$.
After a number of MMT and Magellan runs for follow-up observations,
we have discovered eight new quasars at $z\sim 6$, and are able to for
the first time determine the $z\sim 6$ quasar luminosity function, which
is considerably steeper than that at $z\sim 3-5$, suggesting that at this early
epoch, the growth of supermassive black holes might have started to be limited
by the number of Eddington times available (Extragalactic).
X. Fan, with graudate student L. Xu, continue to collaborate with
S. Gallerini (Budapest), A. Ferrara (SISSA), N. Gnedin (Chicago) on the
theoretical studies of cosmic reionization using high-redshift quasar
spectra. We have been focusing on two key issues: (1) to use the distribution
of dark gaps in quasar absorption spectra to measure the neutral fraction
of the IGM at the reionization epoch; (2) to use proximity effect of high-redshift
quasars to constrain density distributions around these high-mass obejcts
(Extragalactic).
X. Fan, with graduate student L. Jiang, continue to collaborate with
M. Strauss (Princeton), Dean Hines (SSI), L. Hao (Cornell) et al. to work
on a Spitzer survey of the highest redshift quasars. In our Spitzer Cycle 1/3/4 data,we have discovered
a class of $z\sim 6$ quasars without strong hot dust emission.
Considering the cosmic time available for dust formation at $z\sim 6$, it
is likely that we are witnessing the first formation of hot dust torus in
the earliest AGNs. We have just been awarded a Spitzer Cycle-5 program to carry
out a comprehensive survey of narrow-line quasars to test this hypothesis.
In addition, we are also part of a large Hershel GTO Key Project to study
the warm dust properties of a large sample of high-redshift quasars
(Extragalactic).
X. Fan continues to collaborate with C. Carilli, R. Wang (NRAO), F. Walter
(MPIA), P. Cox (IRAM), A. Omont (Paris), F. Bertoldi (MPIfA) et al. to carry out
millimeter and radio surveys of the highest redshift quasars. We have so far
observed most of the known quasars at $z>5.5$ with high sensitivity in
cool dust emission (IRAM) and radio continuum (VLA). We found that over 30\% of
high-redshift quasars have strong dust emission, and if they are heated partly
by star formation, this implies a high star formation rate of a few hundurd
to a few thousand M$_{\odot}$ per year, providing the strongest evidence of
co-formation of the earliest black holes and galaxies in the Unvierse.
We have also detected two additional CO sources among $z\sim 6$ quasars,
giving a first sample of dynamical mass measurements of high-z quasar host
galaxies (Extragalactic).
X. Fan, with graduate student L. Jiang, postdoc fellow M. Vestergaard,
and collaborators F. Walter, J. Kurk (MPIA), M. Strauss (Princeteon),
have carried out a Gemini and VLT near-IR spectroscopic survey of $z\sim 6$
quasars. These high quality IR spectra allow accurate measurements of black hole
masses and estimates of chemical abundances in these quasars. We find,
consistent with previous studies based on small samples, a high BH mass,
high Eddington ratio among the SDSS $z\sim 6$ quasars, accompanied by
super-solar metallicity and non-evolution in abundances, providing further
evidence of a rapid stellar population build-up in the host galaxies.
A side result of this spectroscopic survey is the detection of a slow
evolution in the number density of MgII absorpions (Extragalactic).
X. Fan, with postdoc fellow M. Vestergaard, C. Tremonti, and
graduate student B. Kelly, continue to work on the determination of the evolution
of mass functions of supermassive black holes in the Unvierse.
As part of B. Kelly's Ph.D. thesis, we have developed a new statistical method
to estimate BH mass function based on a Basysian approach that
fully takes into account the survey selection effects and measurement errors.
We have also completely recalibrated the SDSS spectra fitting and BH mass
estimates, and provide the first direct determination of active BH mass function
in the SDSS (Extragalactic).
X. Fan. with graduate student L. Jiang and postdoc fellow M. Vestergaard,
recently studied a rare class of Nitrogen-rich quasars in the SDSS.
Such quasar only represents a few percent of quasar population; they
are likely the most metal-rich quasars as indicated by their strong N emission.
Our new sample increased the total sample size by more than an order of magnitude.
One surprising discovery is that the N-rich quasars are strongly
correlated with strong radio emission of the quasar, hinting that
chemical enrichment of quasar environment and quasar radio activity are
closely related (Extragalactic).
X. Fan has been actively involved in the commissioning and science
demonstration observations of the LBC on LBT. He is leading two LBT/SDT projects,
one on deep imaging of a high-redshift quasar cluster at $z\sim 3.2$, possibily
representating a $\sim 50$ overdensity in the early Universe. This is the
first year project of graduate student F. Bian. We are now moving to carry out
MMT spectroscopic confirmations of the faint quasar candidates discovered
in the LBT observation. Fan is also leading a LBT project of deep imaging
of disk galaxy NGC5907 with a prominent tidal disrupted trails to study the
properties of this tidally disrupted dwarf galaxy (Extragalactic).
X. Fan is the PI on a large LBT project to carry out deep U and Y band
imaging of the entire 9 deg$^2$ of the NOAO Deep-Wide Bootes field.
This is a joint project of Arizona, INAF and LBTB, which has been granted
six LBT nights (plus DD time from LBTO director R. Green).
It is the first large scale survey project to be carried out on the LBT.
The main science goal is to discover the first $z\sim 7$ quasars. In addition,
the survey will allow detailed studies of the evolution of massive galaxies at
$z\sim 1-2$ and Lyman break galaxies at $z\sim 3$ (Extragalactic).
X. Fan continutes to work with R. Thompson, D. Eisenstein, M. Rieke and
R. Kennicutt (Cambridge) on using data from the HUDF NICMOS Treasury program
to constrain contributions from high-redshift sources to the IR background.
Our new calculations show that the 0.8--1.8 micron near infrared background
is due to resolved galaxies in the redshift range $z<8$,
with the majority of power in the redshift range of 0.5--1.5 (Extragalactic)
X. Fan and graduate student L. Jiang is working with
K. Chiu, A. Bunker (AAO), M. Liu, K. Allers (Hawaii), D. Stark, R. Ellis (Caltech) et al.
on following up new candidate quasars and brown dwarfs discovered
in the near-IR UKIDSS survey. We have recently discovered four new faint T dwarfs
from UKIDSS and used these discoverites to constrain to number density of brown dwarfs
(Stellar and Galactic).