14 research outputs found
Diffraction Limited Imaging Spectroscopy of the SgrA* Region using OSIRIS, a new Keck Instrument
We present diffraction limited spectroscopic observations of an infrared
flare associated with the radio source SgrA*. These are the first results
obtained with OSIRIS, the new facility infrared imaging spectrograph for the
Keck Observatory operated with the laser guide star adaptive optics system.
After subtracting the spectrum of precursor emission at the location of Sgr A*,
we find the flare has a spectral index of -2.6 +- 0.9. If we do not subtract
the precursor light, then our spectral index is consistent with earlier
observations by Ghez et al. (2005). All observations published so far suggest
that the spectral index is a function of the flare's K-band flux.Comment: paper accepted for publication in ApJ Letter
Triggered or Self-Regulated Star Formation within Intermediate Redshift Luminous Infrared Galaxies (I). Morphologies and Spatially Resolved Spectral Energy Distributions
We imaged a set of 15 intermediate redshift (z~0.8) luminous infrared
galaxies (LIRGs) with the Keck Laser Guide Star (LGS) AO facility. These
galaxies were selected from the GOODS-S field, allowing us to combine the high
spatial resolution HST optical (B, V, i, and z-bands) images with our
near-infrared (K'-band) images to study the LIRG morphologies and spatially
resolved spectral energy distributions (SEDs). Two thirds of the LIRGs are disk
galaxies, with only one third showing some evidence for interactions, minor, or
major mergers. In contrast with local LIRG disks (which are primarily barred
systems), only 10% of the LIRG disks in our sample contain a prominent bar.
While the optical bands tend to show significant point-like substructure,
indicating distributed star formation, the AO K-band images tend to be smooth.
The SEDs of the LIRGs are consistent with distributed dusty star formation, as
exhibited by optical to IR colors redder than allowed by old stellar
populations alone. This effect is most pronounced in the galaxy cores, possibly
indicating central star formation. We also observed a set of 11 intermediate
redshift comparison galaxies, selected to be non-ellipticals with apparent
K-band magnitudes comparable to the LIRGs. The "normal" (non-LIRG) systems
tended to have lower optical luminosity, lower stellar mass, and more irregular
morphology than the LIRGs. Half of the "normal" galaxies have SEDs consistent
with intermediate aged stellar populations and minimal dust. The other half
show evidence for some dusty star formation, usually concentrated in their
cores. Our work suggests that the LIRG disk galaxies are similar to large disk
systems today, undergoing self regulated star formation, only at 10 - 20 times
higher rates. (Abridged)Comment: Accepted for Publication in AJ. 27 pages, 21 figures, 3 table
Rest-Frame R-band Lightcurve of a z~1.3 Supernova Obtained with Keck Laser Adaptive Optics
We present Keck diffraction limited H-band photometry of a z~1.3 Type Ia
supernova (SN) candidate, first identified in a Hubble Space Telescope (HST)
search for SNe in massive high redshift galaxy clusters. The adaptive optics
(AO) data were obtained with the Laser Guide Star facility during four
observing runs from September to November 2005. In the analysis of data from
the observing run nearest to maximum SN brightness, the SN was found to have a
magnitude H=23.9 +/- 0.14 (Vega). We present the H-band (approximately
rest-frame R) light curve and provide a detailed analysis of the AO photometric
uncertainties. By constraining the aperture correction with a nearby (4"
separation) star we achieve 0.14 magnitude photometric precision, despite the
spatially varying AO PSF.Comment: 11 pages, 8 figures, Accepted for Publication in AJ Updated the
citations, fixed typo
Integral Field Spectroscopy of a Candidate Disk Galaxy at z~1.5 using Laser Guide Star Adaptive Optics
We present 0.1" resolution near-infrared integral field spectroscopy of
Halpha in a z=1.4781 star forming galaxy, Q2343-BM133. These observations were
obtained with OSIRIS (OH Suppressing Infra-Red Imaging Spectrograph) using the
W.M. Keck Observatory Laser Guide Star Adaptive Optics system. Halpha emission
is resolved over a 0.8" (6.8 kpc) x 0.5" (4.3 kpc) region with a 0.1" spatial
resolution. We find a global flux of 4.2+/-0.6x10^{-16} ergs s^{-1} cm^{-2},
and detect a spatially resolved velocity gradient of ~134 km s^{-1} across the
galaxy and a global velocity dispersion of 73+/-9 km s^{-1}. An upper limit of
NII/Halpha < 0.12 is inferred, which implies that this galaxy is not dominated
by an active galactic nucleus and has a metallicity at or below 1/2 solar
metallicity. We derive a star formation rate (SFR) of 47+/-6 Msun yr^{-1}, and
a dereddened SFR of 66+/-9 Msun yr^{-1}. Two-dimensional kinematics for
Q2343-BM133 fit well with an inclined-disk model, with which we estimate an
enclosed mass of 4.3x10^{9} Msun within 5.5 kpc. A possible merger scenario is
also presented, and can not be fully ruled out. We derive a virial mass of
1.1x10^{10} Msun for a disk geometry, using the observed velocity dispersion.
We propose that Q2343-BM133 is currently at an early stage of disk formation at
a look-back time of 9.3 Gyr.Comment: 21 pages, 5 figures, ApJ accepte
Triggered or self-regulated star formation within intermediate redshift luminous infrared galaxies. I. Morphologies and spectral energy distributions
As part of the Center for Adaptive Optics (AO) Treasury Survey (CATS) we imaged a set of 15 intermediate redshift (z ~ 0.8) luminous infrared (IR) galaxies (LIRGs) with the Keck Laser Guide Star (LGS) AO facility. These galaxies were selected from the Great Observatories Origins Deep Survey (GOODS) southern field, allowing us to combine the high spatial resolution Hubble Space Telescope optical (B, V, i, and z-bands) images with our near-infrared (K'-band) images to study the LIRG morphologies and spatially resolved spectral energy distributions (SEDs). Two thirds of the LIRGs are disk galaxies, with only one third showing some evidence for interactions, minor, or major mergers. In contrast with local LIRG disks (which are primarily barred systems), only 10% of the LIRG disks in our sample contain a prominent bar. While the optical bands tend to show a significant point-like substructure, indicating distributed star formation, the AO K-band images tend to be smooth. They lack point-like structures to a K ~ 23.5 limit. This places an upper bound on the number of red super giants per blue knot at less than 4000. The SEDs of the LIRGs are consistent with distributed dusty star formation, as exhibited by optical to IR colors redder than allowed by old stellar populations alone. This effect is most pronounced in the galaxy cores, possibly indicating central star formation. We also observed a set of 11 intermediate redshift comparison galaxies, selected to be non-ellipticals with apparent K-band magnitudes comparable to the LIRGs. The "normal" (non-LIRG) systems tended to have lower optical luminosity, lower stellar mass, and more irregular morphology than the LIRGs. Half of the "normal" galaxies have SEDs consistent with intermediate aged stellar populations and minimal dust. The other half show evidence for some dusty star formation, usually concentrated in their cores. Our work suggests that the LIRG disk galaxies are similar to large disk systems today, undergoing self-regulated star formation, only at 10-20 times higher rates
Near-infrared imaging spectroscopy of the inner few arcseconds of NGC 4151 with OSIRIS at Keck
We present H- and K-band data from the inner arcsecond
of the Seyfert 1.5 galaxy NGC 4151 obtained with the adaptive-optics-assisted
near-infrared-imaging field spectrograph OSIRIS at the Keck Observatory. The angular
resolution is about a few parsecs on-site and thus competes easily with optical images
taken previously with the Hubble Space Telescope. We present the
morphology and dynamics of most species detected but focus on the morphology and dynamics
of the narrow line region (as traced by emission of [FeII]λ1.644
μm), the interplay between plasma ejected from the nucleus (as traced
by 21 cm continuum radio data) and hot H2 gas and characterize the detected
nuclear HeIλ2.058 μm absorption feature as a narrow
absorption line (NAL) phenomenon. The emission from the narrow line region (NLR) as traced
by [FeII] reveals a biconical morphology and we compare the measured dynamics in the
[FeII] emission line with models that propose acceleration of gas in the NLR and simple
ejection of gas into the NLR. In the inner 2.5 arcsec the acceleration model reveals a
better fit to our data than the ejection model. We also see evidence that the jet very
locally enhances emission in [FeII] at certain positions in our field-of-view such that we
were able to distinct the kinematics of these clouds from clouds generally accelerated in
the NLR. Further, the radio jet is aligned with the bicone surface rather than the bicone
axis such that we assume that the jet is not the dominant mechanism responsible for
driving the kinematics of clouds in the NLR. The hot H2 gas is thermal with a
temperature of about 1700 K. We observe a remarkable correlation between individual
H2 clouds at systemic velocity with the 21 cm continuum radio jet. We propose
that the radio jet is at least partially embedded in the galactic disk of NGC 4151 such
that deviations from a linear radio structure are invoked by interactions of jet plasma
with H2 clouds that are moving into the path of the jet because of rotation of
the galactic disk of NGC 4151. Additionally, we observe a correlation of the jet as traced
by the radio data, with gas as traced in Brγ and H2, at
velocities between systemic and ±200 km s-1 at several locations along the path
of the jet. The HeIλ2.058 μm line in NGC 4151 appears in
emission with a blueshifted absorption component from an outflow. The emission
(absorption) component has a velocity offset of 10 km s-1 (−280
km s-1) with a Gaussian (Lorentzian) full-width (half-width) at half maximum
of 160 km s-1 (440 km s-1). The absorption component remains
spatially unresolved and its kinematic measures differ from that of UV resonance
absorption lines. From the amount of absorption we derive a lower limit of the HeI
21S column density of 1 × 1014 cm-2 with a covering
factor along the line-of-sight of Clos ≃ 0.1