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Extragalactic Group Research Sample 2001-2002
(Most recent update: February 2005)
Survey of galaxies by the Infrared Space Observatory Key Project team.
Survey of approximately 60 galaxies of diverse morphological types, luminosities, and blue-to-infrared brightness
ratios. Mid-infrared spectra for 45 disk galaxies have been analyzed, and will be described and compared in a paper written by
N. Lu (IPAC) with several members of the Key Project team.
Infrared Space Observatory
IPAC
Harriet Dinerstein,
G. Helou (PI/IPAC, Caltech), et al.
The Tully-Fisher (TF) relation.
Tully-Fisher is the fundamental scaling relation between luminosity and rotation velocity for disk galaxies. After demonstrating
that spiral galaxies follow correlations between TF offsets and star formation indicators, it has been shown that interacting
galaxies follow the same correlations, provided their velocity profiles are not strongly disturbed in specific quantifiable ways.
Further analysis has uncovered evidence that stellar mass fractions were lower at intermediate redshifts (indirect evidence that
less of the initial gas reservoir had turned into stars).
S. Kannappan,
D. Fabricant (CfA), M. Franx (Leiden), E. Barton Gillespie (ASU)
Bulge growth.
Analysis of the statistics of galaxies whose centers are bluer than their outer parts, suggesting current bulge growth. Established that
the star formation is driven by interactions and mergers rather than internal mechanisms such as bar instabilities.
S. Kannappan,
E. Barton Gillespie (ASU), R. Jansen (ASU)
Pseudobulges.
An observational program to identify and characterize pseudobulges of disk galaxies. These are believed
to form by a different process than do the classical, elliptical-galaxy-like bulges that have been recognized since the time of Hubble.
Bulges, like ellipticals, are thought to form by a series of mergers that trigger dissipative collapse of gas in the progenitor galaxies
followed by starbursts. That is, bulges and ellipticals form rapidly, via dynamically violent events in a galaxy that is far from equilibrium.
In contrast, "pseudobulges" are thought to form by secular evolution of disks that are always close to equilibrium. Nonaxisymmetries
drive gas toward the center and feed star formation that builds up the central stellar density. Instabilities in dense disks then heat
them until they look similar to classical bulges. This is why pseudobulges were not already recognized long ago. However, the more
extreme examples can easily be recognized, because they retain some memory of their disky origin. They rotate more rapidly, in
relation to their random motions, than do classical bulges. A paper on prototypical examples is in preparation. K-band photometry
and internal kinematic measurements of pseudobulge candidates have been obtained with the KPNO 2.1m telescope. This program is in the
data collection stage.
Pseudobulges: Some Bulges Are Really Disks
J. Kormendy,
S. Kannappan,
E. Ambrose
Abundances in dwarf spheroidal galaxies.
This is the largest data set of extra galactic high resolution abundances in dwarf spheroidal galaxies obtained to date. Observations with UVES on UT2.
M. Shetrone,
K. Venn (Macalester College), E. Tolstoy (ESO)
Survey of Draco and Ursa Minor dSph.
Survey using the Hobby-Eberly Telescope to identify the nature of a very red population of RGB stars found
in recent proper motion surveys. Each red spectroscopic member was identified as a previously unidentified CH star missed by
previous carbon star surveys.
M. Shetrone,
P. Cote, P. Stetson
Spectral Principal Component Analysis of a sample of low-redshift PG quasars.
Using HST and ground-based (McDonald Observatory) spectra covering wavelengths from Lyα to Hα, three significant
principal components are identified, and they account for 78% of the total intrinsic variance of the sample. The first principal component
is dominated by emission line cores and is anti-correlated with the luminosity, suggesting that mostly low-velocity gas is involved in the
Baldwin effects. The second principal component represents the UV-optical continuum slope in QSO spectra, which is probably the result
of dust reddening in the QSO environment. the third principal component includes Boroson and Green's "Eigenvector 1" and many
spectral properties in the UV region, such as the line widths of MgII, Lyα and [CIII], and an anti-correlation between UV and optical
FeII emissions. This component may be driven by the Eddington accretion ratio.
Z. Shang,
B. Wills,
E. Robinson
Mass function of supermassive black holes.
Characterization of the mass function of supermassive black holes and their relation to their host galaxy properties; this includes
examining the smallest central black holes by looking for them in globular clusters.
K. Gebhardt
Measurement of large radial dynamics.
Measurement of large radial dynamics using globular cluster systems and the faint stellar light in galaxies to probe the
dark halo and orbital structure. This data involves a substantial amount of time on the HET, providing some of the deepest
spectra ever obtained for diffuse stellar light.
K. Gebhardt, et al.
Distant galaxies.
Comparison of distant galaxies, at redshifts near 1, to nearby galaxies to study evolutionary effects.
K. Gebhardt
Gamma-ray bursts as standard candles.
Two new luminosity indicators (the minimum rise time and the number of peaks) have been theoretically predicted and then
confirmed with two independent sets of bursts. This brings the total number of indicators to four. Simple and general theoretical models to explain
all four luminosity indicators have been presented, along with an off-axis correction based on the observed Epeak value
of the spectrum. The accuracy of bursts as standard candles is now with a one-sigma uncertainty of 0.13 in the log of the derived distances.
B. Schaefer
Gamma-ray burst Hubble Diagram.
The first GRB Hubble Diagram involves nine bursts out to a red shift of 4.5. The shape of this Hubble Diagram is consistent with the flat Ω = 0.3
Universe. The number of bursts are currently too small to be
useful, but this demonstrates the validity of the method. This new method has the great advantage that it extends to very high red shifts and
is impervious to extinction. With the launch of the SWIFT spacecraft in September 2003, 40 bursts
per year are expected to be placed on the diagram, some of which are likely to be in the redshift range of 5-10. Thus, by the end of 2005, the
SWIFT Hubble Diagram Key Project is expected to get 100 bursts in a Hubble Diagram from 0.1 < z < 10. The results will test the
inflationary and quintessence models of the expansion of the Universe.
B. Schaefer
HST and Chandra gamma-ray burst consortium.
Participation in a consortium to study gamma-ray bursts with the Hubble Space Telescope and the Chandra X-ray Observatory.
Observations of GRB 011121 showed evidence for a supernova-like brightening several weeks after the gamma-ray event.
J. Wheeler,
Shri Kulkarni (PI/Caltech)
HET gamma-ray burst consortium.
A consortium has been set up with target of opportunity time on the HET to observe gamma-ray burst afterglows. Observations in
2001/2002 were hampered by weather and the low rate of discovery of optical transients.
J. Wheeler,
B. Schaefer,
P. Hoeflich,
P. Kumar, et al.
ROTSE at McDonald.
One of the four new RObotic Transient Source Experiment (ROTSE) telescopes has been installed at McDonald Observatory
to monitor gamma-ray bursts in their first 100 seconds.
ROTSE Project Home
news release
Gamma Ray Burst Astronomy Opens New Chapter at McDonald
J. Wheeler,
B. Schaefer,
P. Kumar
Low Resolution Spectrograph.
Work was undertaken to accurately measure plate scale and optical distortion self-consistently for the Low Resolution Spectrograph on the HET,
enabling setup on target fields without the need for a pre-image.
G. Hill,
E. Hooper,
J. Tufts,
M. Wolf
Imaging Grism Instrument.
Development of a new multislit spectroscopy capability for the Imaging Grism Instrument on the McDonald 2.7-meter.
Multislit mode was utilized to get redshifts and source classifications for two research projects: the Chandra Multiwavelength Project
(ChaMP), a large serendipitous X-ray survey, and a ground based and HST study of quasar environments.
G. Hill,
E. Hooper,
X-ray survey with B. Wills, B. Wilkes (CfA),
HST study with R. Finn, C. Impey (U. Arizona)
Infrared Space Observatory Project.
Characterization of the spectral energy distributions of AGN.
E. Hooper,
B. Wilkes (CfA)
Cepheid variables in local group galaxies.
Acquisition of low S/N spectra of Cepheid variables in Local Group Galaxies M31 and M33 with the HET has led to the first ever
radial velocity curves for Cepheids in M31 and M33. At this writing a velocity curve for V2203_D31F in M31 is nearly complete and
one for V22665_D33B in M33 is underway. Using statistical techniques on these spectra, extraction of [Fe/H] values has begun.
T. Barnes,
A. Forestell,
C. Sneden, T. Moffett (Purdue Univ.)
Black hole masses and host galaxies in QSOs.
Recent studies of supermassive black holes in nearby galaxies show a tight correlation between black hole mass (MBH)
and the velocity dispersion of the bulge stars (σ) of the host galaxy. The group investigated the evolution of this relationship
since the early universe using the emission lines of low and high redshift QSOs. Black hole masses were derived from the width of the
Hβ emission line, and bulge velocity dispersions from the width of the [OIII] λ5007 Å line from the narrow line region.
The results indicate that the MBH-σ relationship at redshifts z ≈ 2 to 3 was similar to that of recent times.
G. Shields,
K. Gebhardt,
S. Salviander,
B. Wills,
J. Yuan,
B. Xie (Rutgers), M. Brotherton (U. Arizona), M. Dietrich (U. Florida)
Update: February 2005
Black holes in QSOs.
New techniques give the mass of supermassive black holes in active galactic nuclei. This allows study of
black holes in relation to the host galaxies of QSOs. We find little change in the black hole-bulge relationship
for QSOs looking back to redshifts of 2 to 3, when the universe was only 3 billion years old.
Work in progress using CO line widths suggests that at still higher redshifts, very massive black holes exist in comparatively small galaxies.
Knowledge of black hole masses also aids theoretical modeling of the physics of active nuclei. We find that the continuum colors
of QSOs do not agree with the predicted temperature of the accretion disk.
G. Shields,
K. Gebhardt,
S. Salviander,
B. Wills
High velocity clouds in host galaxies.
Program of high resolution observations of supernovae to detect high velocity clouds in host galaxies.
G. Shields,
L. Blitz (U.C. Berkeley), A. Filippenko (U.C. Berkeley), J. Simon (U.C. Berkeley)
"Nuker" collaboration.
A current high priority is a black hole mass measurement in NGC 4258 with HST. The surface photometry required for the measurement
has been carried out.
NGC 4258 is the best BH candidate after our Galaxy - it is the object with the spectacular water maser dynamical BH detection by
Miyoshi et al. (1995). Because the BH mass is so accurately measured using the maser sources, NGC 4258 is the ideal galaxy with
which to demonstrate the accuracy of the Nuker dynamical modeling technique. The BH mass derived from stellar dynamics agrees
very well with the mass found using masers.
Nuker Team Homepage
J. Kormendy,
K. Gebhardt
Dark matter halos of galaxies.
Continued work on the observed correlations between the core radii, central densities, and central velocity dispersions of dark matter
halos of galaxies.
J. Kormendy,
K. Freeman (Australian National U.)
TOOT and TONS.
The TexOx-1000 (TOOT) radio source survey is now about half complete. The survey is already the largest of its kind. The remaining
half of the survey involves faint red galaxies at z > 0.5 that constitute the (possibly unevolving) FRI radio source population at lower
radio powers. These will be observed with HET. The additional TexOx NVSS Survey (TONS) is aimed at obtaining detail on the large-scale
distribution of radio sources, using the fainter NRA VLA Sky Survey. TONS has so far obtained data in three fields: the TOOT08 region,
where we have uncovered two huge (100 Mpc scale) structures in the radio source distribution; the 2dFGRS region, where we are
comparing the bias of radio galaxies with that of field galaxies; and the Subaru XMM Deep Field (SXDF) region. The combined dataset
of these regions already exceeds 300 redshifts.
G. Hill,
S. Rawlings (Oxford),
J. Tufts,
K. Brand (Oxford), E. Mitchell (Oxford)
MUNICS.
The MUNICS project currently has the largest sample of K-band selected galaxies at z < 1 with 5000 photometric redshifts and over
500 spectroscopic redshifts. Further HET and HST observations are planned to map the specific star formation rate (per unit mass)
in a mass-selected sample of field galaxies as a function of redshift.
G. Hill,
R. Bender,
N. Drory,
U. Hopp (Universitäts-Sternwarte München)
Galaxy evolution.
A study of galaxy evolution using the MUNICS dataset.
M. Wolf,
A. Bauer
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