205 research outputs found
On The Fine Tuning and Physical Origin of Line-Locked Absorption Systems in Active Galaxies
Line locking (LL) of absorption line systems is a clear signature of the
dynamical importance of radiation pressure force in driving astrophysical
flows, with recent findings suggesting that it may be common in quasars
exhibiting multiple intrinsic narrow absorption-line (NAL) systems. In this
work we probe the phase space conducive to LL and follow the detailed
kinematics of those systems that may lock at the velocity separation of the CIV
doublet. We find that a small volume of the
phase-phase admits LL, suggesting a high-degree of fine-tuning between the
physical properties of locked systems. The stability of LL against quasar
luminosity variations is quantified with implications for the long-term
variability amplitude of quasars and the velocity-separation statistic between
multiple NAL systems. The high occurrence of LL by the CIV doublet implies that
the hidden extreme-UV emission from quasars is unlikely to be significantly
under-estimated by current models. Further, the ratio of the LL velocity to the
outflow velocity may serve as a powerful constraint on the composition of the
accelerating medium. We conclude that LL poses significant challenges to
current theories for the formation of non-intervening NAL systems, and
speculate that it may be a manifestation of expanding circumstellar shells
around asymptotic giant branch (AGB) stars in the quasar-host bulge.Comment: 22 pages, 13 figures, ApJ in pres
Strong Gravitational Lensing and the Structure of Quasar Outflows
We show that by analyzing the spectra of lensed broad absorption line quasars
(BALQSOs), it is possible to reveal key properties of the outflowing gas in the
inner regions of these objects. This results from the fact that each image of
the quasar corresponds to a different line of sight through the outflow. This
combined with dynamical estimates for the location of the flow, adds new
information concerning the lateral, non line of sight structure of the
absorbing gas. Here we consider a sample of lensed BALQSOs and note that the
similarity of BAL profiles of different images of the same quasar implies that
the flow is relatively isotropic on small scales. We show that its geometry is
inconsistent with the ballistically accelerated spherical cloud model, and that
wind models provide a better description of the flow structure. Furthermore,
observations seem to disagree with naive interpretations of recent
time-dependent wind simulations. This may hint on several important physical
processes that govern the structure and dynamics of such flows. Future
prospects for the study of quasar outflows with the effect of strong
gravitational lensing are discussed.Comment: 4 pages, 1 figure, accepted for publication in ApJ
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
The Dust Content of Galaxy Clusters
We report on the detection of reddening toward z ~ 0.2 galaxy clusters. This
is measured by correlating the Sloan Digital Sky Survey cluster and quasar
catalogs and by comparing the photometric and spectroscopic properties of
quasars behind the clusters to those in the field. We find mean E(B-V) values
of a few times 10^-3 mag for sight lines passing ~Mpc from the clusters'
center. The reddening curve is typical of dust but cannot be used to
distinguish between different dust types. The radial dependence of the
extinction is shallow near the cluster center suggesting that most of the
detected dust lies at the outskirts of the clusters. Gravitational
magnification of background z ~ 1.7 sources seen on Mpc (projected) scales
around the clusters is found to be of order a few per cent, in qualitative
agreement with theoretical predictions. Contamination by different spectral
properties of the lensed quasar population is unlikely but cannot be excluded.Comment: 4 pages, 3 figure
XMM-Newton Spectroscopy of the Starburst Dominated Ultra Luminous Infrared Galaxy NGC 6240
We present new XMM-Newton observation of the Ultra Luminous Infrared Galaxy
(ULIRG) NGC 6240. We analyze the reflecting grating spectrometer (RGS) data,
and data from the other instruments, and find a starburst dominated 0.5-3 keV
spectrum with global properties resembling those observed in M82 but with a
much higher luminosity. We show that the starburst region can be divided into
an outer zone, beyond a radius of about 2.1 kpc, with a gas temperature of
about 10^7 K and a central region with temperatures in the range (2-6) x 10^7
K. The gas in the outer region emits most of the observed Oviii Lyman-alpha
line and the gas in the inner region the emission lines of higher ionization
ions, including a strong Fexxv line. We also identify a small inner part, very
close to the active nuclei, with typical Seyfert 2 properties including a large
amount of photoionized gas producing a strong Fe K-alpha 6.4 keV line. The
combined abundance, temperature and emission measure analysis indicates super
solar Ne/O, Mg/O, Si/O, S/O and possibly also Fe/O. The analysis suggests
densities in the range of (0.07-0.28) x epsilon^(-1/2) cm^(-3) and a total
thermal gas mass of about 4 x 10^8 x epsilon^(1/2) solar masses, where epsilon
is the volume filling factor. We used a simple model to argue that a massive
starburst with an age of about 2 x 10^7 years can explain most of the observed
properties of the source. NGC 6240 is perhaps the clearest case of an X-ray
bright luminous AGN, in a merger, whose soft X-ray spectrum is dominated by a
powerful starburst.Comment: 10 pages, 6 diagrams, accepted by ApJ, added a few minor change
Continuum reverberation mapping of MCG 08-11-011
We report the results from a photometric reverberation mapping campaign
carried out with the C18 telescope at the Wise Observatory from 2019 to 2020,
targeting the active galactic nucleus (AGN) MCG 08-11-011. The monitoring was
conducted on a daily basis with specially designed narrow-band filters,
spanning from optical to near-infrared wavelengths ( to {\AA})
and avoiding prominent broad emission lines. We aim to measure inter-band
continuum time lags, determine the size-wavelength relation, and estimate the
host-subtracted AGN luminosity for this system. We used the point-spread
function photometry to extract the continuum light curves and measure the
inter-band time lags using several methods, including the interpolated
cross-correlation function, the z-transformed discrete correlation function, a
von Neumann estimator, JAVELIN (in spectroscopic and photometric mode), MICA,
and a multivariate correlation function. We find wavelength-dependent lags,
, up to 7 days between the multiband light curves of MCG
08-11-011. The observed lags are larger than predictions based on standard
thin-disk theory by a factor of . We discern a significantly steeper
() size-wavelength relation than the expected for a geometrically thin and optically thick accretion
disk, which may result from the contribution of diffuse continuum emission to
the flux. These results are similar to those found by previous continuum
reverberation mapping campaigns.Comment: arXiv admin note: text overlap with arXiv:2111.0738
Photon Production From The Scattering of Axions Out of a Solenoidal Magnetic Field
We calculate the total cross section for the production of photons from the
scattering of axions by a strong inhomogeneous magnetic field in the form of a
2D delta-function, a cylindrical step function and a 2D Gaussian distribution,
which can be approximately produced by a solenoidal current. The theoretical
result is used to estimate the axion-photon conversion probability which could
be expected in a reasonable experimental situation. The calculated conversion
probabilities for QCD inspired axions are bigger by a factor of 2.67 (for the
cylindrical step function case) than those derived by applying the celebrated
1D calculation of the (inverse) coherent Primakoff effect. We also consider
scattering at a resonance , which corresponds to the
scattering from a delta-function and gives the most enhanced results. Finally,
we analyze the results of this work in the astrophysical extension to suggest a
way in which they may be directed to a solution to some basic solar physics
problems and, in particular, the coronal heating problem.Comment: 19 pages, 1 figure, added analysis of our results in the
astrophysical extensio
- …