55 research outputs found
Observations of quasar host galaxies with laser guide star AO
We report on observations of two quasar host galaxies made with the Lick Observatory adaptive optic system using a laser guide star tuned to the wavelength of the sodium D lines. A brief outline of the system is given, and a description of its performance when obtaining science data. We discuss techniques for obtaining calibration of the point spread function and the analysis steps required to obtain useful scientific results. We present H-band images of quasar host galaxies made with the system. Estimates of the host galaxy magnitudes and central black hole masses were made from these data. These are the first observations of quasar host galaxies with a sodium laser guide star
The Spitzer mid-infrared AGN survey. II-the demographics and cosmic evolution of the AGN population
We present luminosity functions derived from a spectroscopic survey of AGN
selected from Spitzer Space Telescope imaging surveys. Selection in the
mid-infrared is significantly less affected by dust obscuration. We can thus
compare the luminosity functions of the obscured and unobscured AGN in a more
reliable fashion than by using optical or X-ray data alone. We find that the
AGN luminosity function can be well described by a broken power-law model in
which the break luminosity decreases with redshift. At high redshifts
(), we find significantly more AGN at a given bolometric luminosity than
found by either optical quasar surveys or hard X-ray surveys. The fraction of
obscured AGN decreases rapidly with increasing AGN luminosity, but, at least at
high redshifts, appears to remain at \% even at bolometric
luminosities . The data support a picture in which the
obscured and unobscured populations evolve differently, with some evidence that
high luminosity obscured quasars peak in space density at a higher redshift
than their unobscured counterparts. The amount of accretion energy in the
Universe estimated from this work suggests that AGN contribute about 12\% to
the total radiation intensity of the Universe, and a high radiative accretion
efficiency is required to match current
estimates of the local mass density in black holes.Comment: 14 pages, accepted by Ap
Observations of quasar host galaxies with laser guide star AO
We report on observations of two quasar host galaxies made with the Lick Observatory adaptive optic system using a laser guide star tuned to the wavelength of the sodium D lines. A brief outline of the system is given, and a description of its performance when obtaining science data. We discuss techniques for obtaining calibration of the point spread function and the analysis steps required to obtain useful scientific results. We present H-band images of quasar host galaxies made with the system. Estimates of the host galaxy magnitudes and central black hole masses were made from these data. These are the first observations of quasar host galaxies with a sodium laser guide star
Adaptive Optics Imaging Survey of Luminous Infrared Galaxies
We present high resolution imaging observations of a sample of previously
unidentified far-infrared galaxies at z < 0.3. The objects were selected by
cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and
the HST Guide Star Catalog to allow for adaptive optics observations. We found
two new ULIGs (with L_FIR equal to or greater than 10^{12} L_sun) and 19 new
LIGs (with L_FIR equal to or greater than 10^{11} L_sun). Twenty of the
galaxies in the sample were imaged with either the Lick or Keck adaptive optics
systems in H or K'. Galaxy morphologies were determined using the two
dimensional fitting program GALFIT and the residuals examined to look for
interesting structure. The morphologies reveal that at least 30% are involved
in tidal interactions, with 20% being clear mergers. An additional 50% show
signs of possible interaction. Line ratios were used to determine powering
mechanism; of the 17 objects in the sample showing clear emission lines - four
are active galactic nuclei and seven are starburst galaxies. The rest exhibit a
combination of both phenomena.Comment: 29 pages, 8 figures, accepted for publication in A
The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad-Line Region
We present models of the H-emitting broad-line region (BLR) in seven
Seyfert 1 galaxies from the Lick AGN (Active Galactic Nucleus) Monitoring
Project 2011 sample, drawing inferences on the BLR structure and dynamics as
well as the mass of the central supermassive black hole. We find that the BLR
is generally a thick disk, viewed close to face-on, with preferential emission
back toward the ionizing source. The dynamics in our sample range from
near-circular elliptical orbits to inflowing or outflowing trajectories. We
measure black hole masses of for PG 1310108, for Mrk 50,
for Mrk 141, for Mrk 279,
for Mrk 1511, for NGC 4593, and
for Zw 229015. We use these black hole mass
measurements along with cross-correlation time lags and line widths to recover
the scale factor used in traditional reverberation mapping measurements.
Combining our results with other studies that use this modeling technique,
bringing our sample size to 16, we calculate a scale factor that can be used
for measuring black hole masses in other reverberation mapping campaigns. When
using the root-mean-square (rms) spectrum and using the line dispersion to
measure the line width, we find . Finally, we search for correlations between and other AGN
and BLR parameters and find marginal evidence that is correlated with
and the BLR inclination angle, but no significant evidence of a
correlation with the AGN luminosity or Eddington ratio.Comment: 26 pages, 14 figures. Accepted for publication in Ap
The Distance to SN 1999em in NGC 1637 from the Expanding Photosphere Method
We present 30 optical spectra and 49 photometric epochs sampling the first
517 days after discovery of supernova (SN) 1999em, and derive its distance
through the expanding photosphere method (EPM). SN 1999em is shown to be a Type
II-plateau (II-P) event, with a photometric plateau lasting until about 100
days after explosion. We identify the dominant ions responsible for most of the
absorption features seen in the optical portion of the spectrum during the
plateau phase. We find the distance to SN 1999em to be D = 8.2 +/- 0.6 Mpc,
with an explosion date of 5.3 +/- 1.4 days before discovery.
We examine potential sources of systematic error in EPM-derived distances,
and find the most significant to result from uncertainty in the theoretical
modeling of the flux distribution emitted by the SN photosphere (i.e., the
``flux dilution factor''). We compare previously derived EPM distances to 5 SNe
II in galaxies for which a recently revised Cepheid distance exists from the
HST Key Project and find D(Cepheids) / D(EPM) = 0.96 +/- 0.09. Finally, we
investigate the possible use of SNe II-P as standard candles and find that for
8 photometrically confirmed SNe II-P with previously derived EPM distances and
SN 1999em, the mean plateau absolute brightness is M_V(plateau) = -16.4 +/- 0.6
mag, implying that distances good to ~30% (1-sigma) may be possible without the
need for a complete EPM analysis. At M_V(plateau) = -15.9 +/- 0.2 mag, SN
1999em is somewhat fainter than the average SN II-P. The general consistency of
absolute SNe II-P brightness during the plateau suggests that the standard
candle assumption may allow SNe II-P to be viable cosmological beacons at z >
2.Comment: 79 pages, 26 figures, accepted for publication in the Publications of
the Astronomical Society of the Pacifi
Early-time Spectropolarimetry of the Asymmetric Type II Supernova SN 2023ixf
We present six epochs of optical spectropolarimetry of the Type II supernova
(SN) 2023ixf ranging from 2 to 15 days after the explosion. Polarimetry
was obtained with the Kast double spectrograph on the Shane 3 m telescope at
Lick Observatory, representing the earliest such observations ever captured for
an SN. We observe a high continuum polarization %
on days +1.4 and +2.5 before dropping to 0.5 % on day +3.5, persisting at that
level up to day +14.5. Remarkably, this change coincides temporally with the
disappearance of highly ionized "flash" features. The decrease of the continuum
polarization is accompanied by a rotation of the polarization
position angle () as seen across the continuum. The early evolution of the
polarization may indicate different geometric configurations of the
electron-scattering atmosphere as seen before and after the disappearance of
the emission lines associated with highly-ionized species (e.g., He II, C IV, N
III), which are likely produced by elevated mass loss shortly prior to the SN
explosion. We interpret the rapid change of polarization and from days
+2.5 to +4.5 as the time when the SN ejecta emerge from the dense asymmetric
circumstellar material (CSM). The temporal evolution of the continuum
polarization and the is consistent with an aspherical SN explosion that
exhibits a distinct geometry compared to the CSM. The rapid follow-up
spectropolarimetry of SN 2023ixf during the shock ionization phase reveals an
exceptionally asymmetric mass-loss process leading up to the explosion.Comment: Submitted to Ap
The Lick AGN Monitoring Project: Reverberation Mapping of Optical Hydrogen and Helium Recombination Lines
We have recently completed a 64-night spectroscopic monitoring campaign at
the Lick Observatory 3-m Shane telescope with the aim of measuring the masses
of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected
masses in the range ~10^6-10^7M_sun and also the well-studied nearby active
galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including
NGC 5548) showed optical variability of sufficient strength during the
monitoring campaign to allow for a time lag to be measured between the
continuum fluctuations and the response to these fluctuations in the broad
Hbeta emission, which we have previously reported. We present here the light
curves for the Halpha, Hgamma, HeII 4686, and HeI 5876 emission lines and the
time lags for the emission-line responses relative to changes in the continuum
flux. Combining each emission-line time lag with the measured width of the line
in the variable part of the spectrum, we determine a virial mass of the central
supermassive black hole from several independent emission lines. We find that
the masses are generally consistent within the uncertainties. The time-lag
response as a function of velocity across the Balmer line profiles is examined
for six of the AGNs. Finally we compare several trends seen in the dataset
against the predictions from photoionization calculations as presented by
Korista & Goad. We confirm several of their predictions, including an increase
in responsivity and a decrease in the mean time lag as the excitation and
ionization level for the species increases. Further confirmation of
photoionization predictions for broad-line gas behavior will require additional
monitoring programs for these AGNs while they are in different luminosity
states. [abridged]Comment: 37 pages, 18 figures and 15 tables, accepted for publication in the
Astrophysical Journa
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