2,894 research outputs found
Near infrared imaging of the broad absorption line quasar BAL QSO 0134+3253
In this paper we present near infrared (NIR) imaging data of the host galaxy
of the broad absorption line quasar (BALQ) at z=2.169, serendipitously found
close to 3C48. The data were obtained with the ESO-VLT camera ISAAC during
period 67. We find extended, rest-frame optical emission around the BALQ after
subtracting a scaled stellar point spread function from the quasar nucleus in
J, H, and Ks. The extended rest-frame optical emission can be interpreted as an
approximately 2 Gyr old stellar population composing the host galaxy of the
BALQ or a stellar population of similar age associated with an intermediate
(z=1.667) absorption system spectroscopically identified by Canalizo & Stockton
(1998) simultaneously. The rest-frame-UV emission on the other hand is
dominated by a young, 500 Myr old stellar population. The UV/optical colors
resemble a mixture of the two populations, of which the young one accounts for
about 80%. Assuming that the residual emission is located at the BALQ redshift,
we find that the host galaxy has a resolved flux of about 10% of the BALQ flux.
The physical scale is quite compact, typical for radio quiet QSOs or Lyman
break galaxies at these redshifts, indicating that the systems are still in the
process of forming.Comment: 14 pages, referee style, 6 figures, 4 tables, accepted for
publication in A&
Reconstruction of Stellar Orbits Close to Sagittarius A*: Possibilities for Testing General Relativity
We have reconstructed possible orbits for a collection of stars located
within 0.5 arcsec of Sgr A*. These orbits are constrained by observed stellar
positions and angular proper motions. The construction of such orbits serves as
a baseline from which to search for possible deviations due to the unseen mass
distribution in the central 1000 AU of the Galaxy. We also discuss the
likelihood that some of these stars may eventually exhibit detectable
relativistic effects, allowing for interesting tests of general relativity
around the 2.6 x 10^6 solar mass central object.Comment: 20 pages, 5 figures submitted to Astrophysical Journal, substantial
changes and additions based on referee's comment
A Black Hole in the Galactic Center Complex IRS 13E?
The IRS 13E complex is an unusual concentration of massive, early-type stars
at a projected distance of ~0.13 pc from the Milky Way's central supermassive
black hole Sagittarius A* (Sgr A*). Because of their similar proper motion and
their common nature as massive, young stars it has recently been suggested that
IRS 13E may be the remnant of a massive stellar cluster containing an
intermediate-mass black hole (IMBH) that binds its members gravitationally in
the tidal field of Sgr A*. Here, we present an analysis of the proper motions
in the IRS~13E environment that combines the currently best available data with
a time line of 10 years. We find that an IMBH in IRS 13E must have a minimum
mass of ~10^4 solar masses in order to bind the source complex gravitationally.
This high mass limit in combination with the absence so far of compelling
evidence for a non-thermal radio and X-ray source in IRS 13E make it appear
unlikely that an IMBH exists in IRS 13E that is sufficiently massive to bind
the system gravitationally.Comment: accepted by AP
Research on Computational and Display Requirements for Human Control of Space Vehicle Boosters, Phase III. Part II - Computer Programs and Data Package Final Report, 1 Mar. - 31 Aug. 1967
Hybrid computer program for real time trajectory determination of human controlled space vehicle booste
L- and M-band imaging observations of the Galactic Center region
We present near-infrared H-, K-, L- and M-band photometry of the Galactic
Center from images obtained at the ESO VLT in May and August 2002, using the
NAOS/CONICA (H and K) and the ISAAC (L and M) instruments. The large field of
view (70" x 70") of the ISAAC instrument and the large number of sources
identified (L-M data for 541 sources) allows us to investigate colors, infrared
excesses and extended dust emission. Our new L-band magnitude calibration
reveals an offset to the traditionally used calibrations, which we attribute to
the use of the variable star IRS7 as a flux calibrator. Together with new
results on the extinction towards the Galactic Center (Scoville et al. 2003;
Raab 2000), our magnitude calibration results in stellar color properties
expected from standard stars and removes any necessity to modify the K-band
extinction. The large number of sources for which we have obtained L-M colors
allows us to measure the M-band extinction to A_M=(0.056+-0.006)A_V
(approximately =A_L), a considerably higher value than what has so far been
assumed. L-M color data has not been investigated previously, due to lack of
useful M-band data. We find that this color is a useful diagnostic tool for the
preliminary identification of stellar types, since hot and cool stars show a
fairly clear L-M color separation. This is especially important if visual
colors are not available, as in the Galactic Center. For one of the most
prominent dust embedded sources, IRS3, we find extended L- and M-band continuum
emission with a characteristic bow-shock shape. An explanation for this
appearance is that IRS3 consists of a massive, hot, young mass-losing star
surrounded by an optically thick, extended dust shell, which is pushed
northwest by wind from the direction of the IRS16 cluster and SgrA*.Comment: 24 pages, 7 figures, 2 tables, accepted for publication in Astronomy
& Astrophysic
Resolving the Host Galaxy of the Nearby QSO I Zw 1 with Sub-Arcsecond Multi-Transition Molecular Line Observations
We present the first sub-kpc 0.7" (~ 850 pc) resolution 12CO(1-0) molecular
line observations of the ISM in the host galaxy of the QSO I Zw 1. The
observations were obtained with the BIMA mm-interferometer in its compact A
configuration. The BIMA data are complemented by new observations of the
12CO(2-1) and 13CO(1-0) line with IRAM Plateau de Bure mm-interferometer (PdBI)
at 0.9" and 1.9" resolution, respectively. These measurements, which are part
of a multi-wavelength study of the host galaxy of I Zw 1, are aimed at
comparing the ISM properties of a QSO host with those of nearby galaxies as
well as to obtain constraints on galaxy formation/evolution models. Our images
of the 12CO(1-0) line emission show a ring-like structure in the circumnuclear
molecular gas distribution with an inner radius of about 1.2 kpc. The presence
of such a molecular gas ring was predicted from earlier lower angular
resolution PdBI 12CO(1-0) observations. A comparison of the BIMA data with IRAM
PdBI 12CO(2-1) observations shows variations in the excitation conditions of
the molecular gas in the innermost 1.5" comprising the nuclear region of I Zw
1. The observed properties of the molecular cloud complexes in the disk of the
host galaxy suggest that they can be the sites of massive circumnuclear star
formation, and show no indications of excitation by the nuclear AGN. This all
indicates that the molecular gas in a QSO host galaxy has similar properties to
the gas observed in nearby low luminosity AGNs.Comment: to be published in ApJ 1 July 2004 issu
Simultaneous NIR/sub-mm observation of flare emission from SgrA*
We report on a successful, simultaneous observation and modeling of the
sub-millimeter to near-infrared flare emission of the Sgr A* counterpart
associated with the super-massive black hole at the Galactic center. Our
modeling is based on simultaneous observations that have been carried out on 03
June, 2008 using the NACO adaptive optics (AO) instrument at the ESO VLT and
the LABOCA bolometer at the APEX telescope. Inspection and modeling of the
light curves show that the sub-mm follows the NIR emission with a delay of
1.5+/-0.5 hours. We explain the flare emission delay by an adiabatic expansion
of the source components.Comment: 12 pages, 9 figures, 3 tables, in press with A&
Coordinated NIR/mm observations of flare emission from Sagittarius A*
We report on a successful, simultaneous observation and modelling of the
millimeter (mm) to near-infrared (NIR) flare emission of the Sgr A* counterpart
associated with the supermassive black hole at the Galactic centre (GC). We
present a mm/sub-mm light curve of Sgr A* with one of the highest quality
continuous time coverages and study and model the physical processes giving
rise to the variable emission of Sgr A*.Comment: 14 pages, 16 figure
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