174 research outputs found
MUSE-inspired view of the quasar Q2059-360, its Lyman alpha blob, and its neighborhood
The radio-quiet quasar Q2059-360 at redshift is known to be close to
a small Lyman blob (LAB) and to be absorbed by a proximate damped
Ly (PDLA) system.
Here, we present the Multi Unit Spectroscopic Explorer (MUSE) integral field
spectroscopy follow-up of this quasi-stellar object (QSO). Our primary goal is
to characterize this LAB in detail by mapping it both spatially and spectrally
using the Ly line, and by looking for high-ionization lines to
constrain the emission mechanism.
Combining the high sensitivity of the MUSE integral field spectrograph
mounted on the Yepun telescope at ESO-VLT with the natural coronagraph provided
by the PDLA, we map the LAB down to the QSO position, after robust subtraction
of QSO light in the spectral domain.
In addition to confirming earlier results for the small bright component of
the LAB, we unveil a faint filamentary emission protruding to the south over
about 80 pkpc (physical kpc); this results in a total size of about 120 pkpc.
We derive the velocity field of the LAB (assuming no transfer effects) and map
the Ly line width. Upper limits are set to the flux of the N V , C IV , He II , and C III] lines. We have discovered two probable Ly emitters at the
same redshift as the LAB and at projected distances of 265 kpc and 207 kpc from
the QSO; their Ly luminosities might well be enhanced by the QSO
radiation. We also find an emission line galaxy at near the line of
sight to the QSO.
This LAB shares the same general characteristics as the 17 others surrounding
radio-quiet QSOs presented previously. However, there are indications that it
may be centered on the PDLA galaxy rather than on the QSO.Comment: Accepted for publication in Astronomy & Astrophysics; 16 pages, 19
figure
Spectroscopy of extended Ly\alpha\ envelopes around z=4.5 quasars
What are the frequency, shape, kinematics, and luminosity of Ly\alpha\
envelopes surrounding radio-quiet quasars at high redshift, and is the
luminosity of these envelopes related to that of the quasar or not? As a first
step towards answering these questions, we have searched for Ly\alpha\
envelopes around six radio-quiet quasars at z~4.5, using deep spectra taken
with the FORS2 spectrograph attached to the UT1 of the Very Large Telescope
(VLT). Using the multi-slit mode allows us to observe several point spread
function stars simultaneously with the quasar, and to remove the point-like
emission from the quasar, unveiling the faint underlying Ly\alpha\ envelope
with unprecedented depth. An envelope is detected around four of the six
quasars, which suggests that these envelopes are very frequent. Their diameter
varies in the range 26<d<64 kpc, their surface brightness in the range
3x10^{-19}<\mu<2x10^{-17} erg/s/cm^2/arcsec^2, and their luminosity in the
range 10^{42}<L(Ly\alpha)<10^{44} erg/s. Their shape may be strongly
asymmetric. The Ly\alpha\ emission line full width at half maximum (FWHM) is
900<FWHM<2200 km/s and its luminosity correlates with that of the broad line
region (BLR) of the quasar, with the notable exception of BR2237-0607, the
brightest object in our sample. The same holds for the relation between the
envelope Ly\alpha\ luminosity and the ionizing luminosity of the quasar. While
the deep slit spectroscopy presented in this paper is very efficient at
detecting very faint Ly\alpha\ envelopes, narrow-band imaging is now needed to
measure accurately their spatial extent, radial luminosity profile, and total
luminosity. These observables are crucial to help us discriminate between the
three possible radiation processes responsible for the envelope emission: (i)
cold accretion, (ii) fluorescence induced by the quasar, and (iii) scattering
of the BLR photons by cool gas.Comment: 10 pages, 5 figures, accepted for publication in Astronomy &
Astrophysic
Narrow Components within the Fe Kalpha Profile of NGC 3516: Evidence for the Importance of General Relativistic Effects?
We present results from a simultaneous Chandra HETG and XMM-Newton
observation of NGC 3516. We find evidence for several narrow components of Fe
Kalpha along with a broad line. We consider the possibility that the lines
arise in an blob of material ejected from the nucleus with velocity ~0.25c. We
also consider an origin in a neutral accretion disk, suffering enhanced
illumination at 35 and 175 gravitational radii, perhaps due to magnetic
reconnection. The presence of these narrow features indicates there is no
Comptonizing region along the line-of-sight to the nucleus. This in turn is
compelling support for the hypothesis that broad Fe Kalpha components are, in
general, produced by strong gravity.Comment: 12 pages, 3 color figures. LaTeX with postscript figures. Resubmitted
June 7 2002, to Astrophysical Journal Letter
Deep optical spectroscopy of extended Lyman alpha emission around three radio-quiet z=4.5 quasars
We report the first results of a spectroscopic search for Lyman alpha,
envelopes around three z=4.5 radio-quiet quasars. Our observational strategy
uses the FORS2 spectrograph attached to the UT1 of the Very Large Telescope
(VLT) in the multi-slit mode. This allows us to observe simultaneously the
quasars and several PSF stars. The spectra of the latter are used to remove the
point-like quasar from the data, and to unveil the faint underlying Lyman
alpha, envelopes associated with the quasars with unprecedented depth. We
clearly detect an envelope around two of the three quasars. These envelopes
measure respectively 10" and 13" in extent (i.e. 67 kpc and 87 kpc). This is 5
to 10 times larger than predicted by the models of Haiman & Rees (2001) and up
to 100 times fainter. Our observations better agree with models involing a
clumpy envelope as in Alam & Miralda-Escude (2002) or Chelouche et al. (2008).
We find that the brighter quasars also have the brighter envelopes but that the
extend of the envelopes does not depend on the quasar luminosity. Although our
results are based on only two objects with a detected Lyman alpha, envelope,
the quality of the spatial deblending of the spectra lends considerable hope to
estimate the luminosity function and surface brightness profiles of high
redshift Lyman alpha, envelopes down to F= 2-3 10^{-21} erg/s/cm^2/A. We find
that the best strategy to carry out such a project is to obtain both
narrow-band images and deep slit-spectra.Comment: 8 pages, 5 figures, submitted to A&
Revealing the structure of the lensed quasar Q 0957+561 III. Constraints on the size of the broad-line region
Our aim is to examine the size, kinematics, and geometry of the broad-line
region (BLR) in the double-lensed quasar Q 0957+561 by analyzing the impact of
microlensing on various rest-frame ultraviolet broad-emission lines (BELs). We
explore the influence of intrinsic variability and microlensing on the C IV, C
III], and Mg II emission lines through multiple spectroscopic observations
taken between April 1999 and January 2017. By utilizing the line cores as a
reference for no microlensing and correcting for the long time delay between
the images, we estimate the sizes of the regions emitting the broad-line wings
using a Bayesian approach. Our study of the microlensing amplitudes between the
lensed images of the quasar Q 0957+561 reveals differing sizes of the regions
emitting the three prominent BELs C IV, C III], and Mg II. The strength of the
differential microlensing indicates that the high-ionization line C IV arises
from a compact inner region of the BLR with a half-light radius of lt-days, which represents a lower limit on the overall size of
the BLR and is comparable to the size of the region emitting the r-band
continuum in this system. A somewhat larger size of lt-days
is obtained for the semi-forbidden line C III]. Microlensing has a weak impact
on the lower-ionization line Mg II, which is emitted from a region with a
half-light radius of lt-days. These findings suggest that
the BEL regions may have distinct geometries and kinematics, with the more
extended ones being spherically symmetric, and the most compact ones being
nonspherical, with motions likely confined to a plane
On the Connection Between Metal Absorbers and Quasar Nebulae
We establish a simple model for the distribution of cold gas around L*
galaxies using a large set of observational constraints on the properties of
strong MgII absorber systems. Our analysis suggests that the halos of L*
galaxies are filled with cool gaseous clouds having sizes of order 1kpc and
densities of ~10^{-2} cm^{-3}. We then investigate the physical effects of
cloud irradiation by a quasar and study the resulting spectral signatures. We
show that quasar activity gives rise to (i) extended narrow-line emission on
~100kpc scales and (ii) an anisotropy in the properties of the absorbing gas
arising from the geometry of the quasar radiation field. Provided that quasars
reside in halos several times more massive than those of L* galaxies, our model
predictions appear to be in agreement with observations of narrow emission-line
nebulae around quasars and the recent detections of ~100kpc cold gaseous
envelopes around those objects, suggesting a common origin for these phenomena.
We discuss the implications of our results for understanding absorption
systems, probing quasar environments at high redshifts, and testing the quasar
unification scheme.Comment: 15 pages, 13 figures (ApJ submitted
Axion-like particle effects on the polarization of cosmic high-energy gamma sources
Various satellite-borne missions are being planned whose goal is to measure
the polarization of a large number of gamma-ray bursts (GRBs). We show that the
polarization pattern predicted by current models of GRB emission can be
drastically modified by the existence of very light axion-like particles
(ALPs), which are present in many extensions of the Standard Model of particle
physics. Basically, the propagation of photons emitted by a GRB through cosmic
magnetic fields with a domain-like structure induces photon-ALP mixing, which
is expected to produce a strong modification of the original photon
polarization. Because of the random orientation of the magnetic field in each
domain, this effect strongly depends on the orientation of the photon line of
sight. As a consequence, photon-ALP conversion considerably broadens the
original polarization distribution. Searching for such a peculiar feature
through future high-statistics polarimetric measurements is therefore a new
opportunity to discover very light ALPs.Comment: Final version (21 pages, 8 eps figures). Matches the version
published on JCAP. Added a Section on the effects of cosmic expansion on
photon-ALP conversions. Figures modified to take into account this effect.
References updated. Conclusions unchanged
Supernova PTF12glz: a possible shock breakout driven through an aspherical wind
We present visible-light and ultraviolet (UV) observations of the supernova
PTF12glz. The SN was discovered and monitored in near-UV and R bands as part of
a joint GALEX and Palomar Transient Factory campaign. It is among the most
energetic Type IIn supernovae observed to date (~10^51erg). If the radiated
energy mainly came from the thermalization of the shock kinetic energy, we show
that PTF12glz was surrounded by ~1 solar mass of circumstellar material (CSM)
prior to its explosive death. PTF12glz shows a puzzling peculiarity: at early
times, while the freely expanding ejecta are presumably masked by the optically
thick CSM, the radius of the blackbody that best fits the observations grows at
~8000km/s. Such a velocity is characteristic of fast moving ejecta rather than
optically thick CSM. This phase of radial expansion takes place before any
spectroscopic signature of expanding ejecta appears in the spectrum and while
both the spectroscopic data and the bolometric luminosity seem to indicate that
the CSM is optically thick. We propose a geometrical solution to this puzzle,
involving an aspherical structure of the CSM around PTF12glz. By modeling
radiative diffusion through a slab of CSM, we show that an aspherical geometry
of the CSM can result in a growing effective radius. This simple model also
allows us to recover the decreasing blackbody temperature of PTF12glz.
SLAB-Diffusion, the code we wrote to model the radiative diffusion of photons
through a slab of CSM and evaluate the observed radius and temperature, is made
available on-line.Comment: Sumbitted to ApJ. Comments are welcom
The Great Slump : Mrk 926 reveals discrete and varying Balmer line satellite components during a drastic phase of decline
This work has been supported by the DFG grants KO857/35-1 and CH71/34-3. K. H. acknowledges support from STFC grant ST/M001296/1. D. C. acknowledges support from ISF grant 2398/19.Aims. Mrk 926 is known to be a highly variable active galactic nucleus. Furthermore, it is known to show very broad line profiles. We intended to study the continuum and line profile variations of this object with high temporal resolution in order to determine its broad-line region structure and to derive its black hole mass. Methods. We carried out a high-cadence spectroscopic variability campaign of Mrk 926 with the 10m HET telescope, aided by photometric V-band data taken with the C18 telescope at the Wise Observatory, over a period of about five months. We extracted spectroscopic continuum and line light curves, and computed cross-correlation functions (CCFs) as well as velocity-resolved CCFs with respect to the combined spectroscopic and photometric V-band light curve. Results. The continuum luminosity of Mrk 926 showed a drastic decrease during our campaign. The luminosity dropped to less than 50% of its original luminosity within only 2.5 months. Furthermore, the spectra of Mrk 926 show complex and very broad Balmer line profiles, including outer Balmer satellites ranging from ±5000 to ±13â000 km sâ1. The integrated Hα, HÎČ, and HeâŻIλ5876 line light curves are delayed relative to the continuum light curve. The Hα and HÎČ lines show two velocity-delay structures in the central part of their line profile (within ±5000 km sâ1), at âŒ10 and âŒ57 light-days and at âŒ5 and âŒ48 light-days, respectively. These structures might be interpreted as the upper and lower halves of an ellipse in the velocity-delay plane, which might be the signature of a line-emitting ring, inclined by âŒ50° to the line of sight and orbiting the black hole at radii, R, of 33.5 and 26.5 light-days. We determined continuum luminosities, log(λâLλ/ergâsâ1), of 43.68â44.13, which are in good agreement with the established RBLRâ
ââ
LAGN relation. Adopting delays of 33.5 and 26.5 days for Hα and HÎČ, respectively, we derive a black hole mass of (1.1â
屉
0.2)Ă108âMâ; this indicates a low Eddington ratio, which decreased from 8 to 3 percent during our campaign. The Balmer satellite components show a higher correlation coefficient with respect to the continuum than the central line profile, and their response to the continuum variations is on the order of only 3â
ââ
5 days. We attribute this to the central line segment and the Balmer satellites having different, spatially distinct regions of origin.Publisher PDFPeer reviewe
- âŠ