296 research outputs found
A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255: I. C IV absorption variability
Broad Absorption Lines indicate gas outflows with velocities from thousands
km/s to about 0.2 the speed of light, which may be present in all quasars and
may play a major role in the evolution of the host galaxy. The variability of
absorption patterns can provide informations on changes of the density and
velocity distributions of the absorbing gas and its ionization status. We
collected 23 photometrical and spectro-photometrical observations at the 1.82m
Telescope of the Asiago Observatory since 2003, plus other 5 spectra from the
literature. We analysed the evolution in time of the equivalent width of the
broad absorption feature and two narrow absorption systems, the correlation
among them and with the R band magnitude. We performed a structure function
analysis of the equivalent width variations. We present an unprecedented
monitoring of a broad absorption line quasar based on 28 epochs in 14 years.
The shape of broad absorption feature shows a relative stability, while its
equivalent width slowly declines until it sharply increases during 2011. In the
same time the R magnitude stays almost constant until it sharply increases
during 2011. The equivalent width of the narrow absorption redwards of the
systemic redshift only shows a decline. The broad absorption behaviour suggests
changes of the ionisation status as the main cause of variability. We show for
the first time a correlation of this variability with the R band flux. The
different behaviour of the narrow absorption system might be due to
recombination time delay. The structure function of the absorption variability
has a slope comparable with typical optical variability of quasars. This is
consistent with variations of the 200 A ionising flux originating in the inner
part of the accretion disk.Comment: 10 pages, 8 figures, to appear on Astronomy & Astrophysic
The rest-frame UV-to-optical spectroscopy of APM 08279+5255 - BAL classification and black hole mass estimates
We present the analysis of the rest-frame optical-to-UV spectrum of APM
08279+5255, a well-known lensed broad absorption line (BAL) quasar at . The spectroscopic data are taken with the optical DOLoRes and near-IR
NICS instruments at TNG, and include the previously unexplored range between C
III] 1910 and [O III] 4959,5007. We investigate the
possible presence of multiple BALs by computing "balnicity" and absorption
indexes (i.e. BI, BI and AI) for the transitions Si IV 1400, C IV
1549, Al III 1860 and Mg II 2800. No clear evidence
for the presence of absorption features is found in addition to the already
known, prominent BAL associated to C IV, which supports a high-ionization BAL
classification for APM 08279+5255. We also study the properties of the [O III],
H and Mg II emission lines. We find that [O III] is intrinsically weak
(), as it is typically found in
luminous quasars with a strongly blueshifted C IV emission line (2500 km
s for APM 08279+5255). We compute the single-epoch black hole mass based
on Mg II and H broad emission lines, finding M, with the magnification factor that can
vary between 4 and 100 according to CO and rest-frame UV-to-mid-IR imaging
respectively. Using a Mg II equivalent width (EW)-to-Eddington ratio relation,
the EW \AA\ measured for APM 08279+5255 translates into an
Eddington ratio of 0.4, which is more consistent with . This
magnification factor also provides a value of that is consistent
with recent reverberation-mapping measurements derived from C IV and Si IV.Comment: 10 pages, 4 figures, 4 tables, accepted for publication in A&
Serendipitous discovery of a projected pair of QSOs separated by 4.5 arcsec on the sky
We present the serendipitous discovery of a projected pair of quasi-stellar
objects (QSOs) with an angular separation of arcsec. The
redshifts of the two QSOs are widely different: one, our programme target, is a
QSO with a spectrum consistent with being a narrow line Seyfert 1 AGN at
. For this target we detect Lyman-, \ion{C}{4}, and
\ion{C}{3]}. The other QSO, which by chance was included on the spectroscopic
slit, is a Type 1 QSO at a redshift of , for which we detect
\ion{C}{4}, \ion{C}{3]} and \ion{Mg}{2}. We compare this system to previously
detected projected QSO pairs and find that only about a dozen previously known
pairs have smaller angular separation.Comment: 4 pages, 3 figures. Accepted for publication in A
The High A(V) Quasar Survey: Reddened quasi-stellar objects selected from optical/near-infrared photometry - II
Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are
reddened by dust either in their host galaxies or in intervening absorber
galaxies are to a large degree missed by optical color selection criteria like
the one used by the Sloan Digital Sky Survey (SDSS). To overcome this bias
against red QSOs, we employ a combined optical and near-infrared color
selection. In this paper, we present a spectroscopic follow-up campaign of a
sample of red candidate QSOs which were selected from the SDSS and the UKIRT
Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS
photometry are supplemented by mid-infrared photometry from the Wide-field
Infrared Survey Explorer. In our sample of 159 candidates, 154 (97%) are
confirmed to be QSOs. We use a statistical algorithm to identify sightlines
with plausible intervening absorption systems and identify nine such cases
assuming dust in the absorber similar to Large Magellanic Cloud sightlines. We
find absorption systems toward 30 QSOs, 2 of which are consistent with the
best-fit absorber redshift from the statistical modeling. Furthermore, we
observe a broad range in SED properties of the QSOs as probed by the rest-frame
2 {\mu}m flux. We find QSOs with a strong excess as well as QSOs with a large
deficit at rest-frame 2 {\mu}m relative to a QSO template. Potential solutions
to these discrepancies are discussed. Overall, our study demonstrates the high
efficiency of the optical/near-infrared selection of red QSOs.Comment: 64 pages, 18 figures, 16 pages of tables. Accepted to ApJ
Capturing dual AGN activity and kiloparsec-scale outflows in IRAS 20210+1121
The most standard scenario for the evolution of massive galaxies across cosmic time assumes a correspondence based on the interplay between active galactic nuclei (AGN) feedback, which injects large amounts of energy into the host environment, and galaxy mergers, with their ability to trigger massive star formation events and accretion onto supermassive black holes. Interacting systems hosting AGN are useful laboratories for obtaining key insights into both phenomena. In this context, we present an analysis of the optical spectral properties of IRAS 20210+1121 (I20210), a merging system at z = 0.056. According to X-ray data, this object comprises two interacting galaxies, each hosting an obscured AGN. The optical spectra confirm the presence of AGN features in both galaxies. In particular, we are able to provide a Seyfert classification for I20210 North. The spectrum of I20120 South shows broad blueshifted components associated with the most intense emission lines that indicate the presence of an ionized outflow, for which we derive a maximum velocity of ∼2000 km s-1, an extension of ∼2 kpc, and a mass rate of ∼0.6 M⊙ yr-1. We also report the existence of an ionized nebular component with v ∼ 1000 km s-1 at ∼6.5 kpc southwards of I20210 South, which can be interpreted as disrupted gas ejected from the host galaxy by the action of the outflow. I20120 therefore exhibits a double obscured AGN, with one of them showing evidence of ongoing events for AGN-powered outflows. Future spatially resolved spectroscopy will allow for an accurate mapping of the gas kinematics in this AGN pair and evaluate the impact of the outflow on both the interstellar medium and the galaxy environment
Bronchial glomus tumor mimicking a COPD exacerbation
We report the case of a glomus tumor originating in the left main bronchus diagnosed in a 79 year old Caucasian man. A glomus tumor is an extremely rare neoplasm in the bronchi with nonspecific clinical features. Bronchoscopy allows the diagnosis through biopsy and subsequent histopathological examination of the tissue and in selected cases may represent a valid alternative to surgery permitting a radical tumor excision
Probing extreme environments with the Cherenkov Telescope Array
The physics of the non-thermal Universe provides information on the
acceleration mechanisms in extreme environments, such as black holes and
relativistic jets, neutron stars, supernovae or clusters of galaxies. In the
presence of magnetic fields, particles can be accelerated towards relativistic
energies. As a consequence, radiation along the entire electromagnetic spectrum
can be observed, and extreme environments are also the most likely sources of
multi-messenger emission. The most energetic part of the electromagnetic
spectrum corresponds to the very-high-energy (VHE, E>100 GeV) gamma-ray regime,
which can be extensively studied with ground based Imaging Atmospheric
Cherenkov Telescopes (IACTs). The results obtained by the current generation of
IACTs, such as H.E.S.S., MAGIC, and VERITAS, demonstrate the crucial importance
of the VHE band in understanding the non-thermal emission of extreme
environments in our Universe. In some objects, the energy output in gamma rays
can even outshine the rest of the broadband spectrum. The Cherenkov Telescope
Array (CTA) is the next generation of IACTs, which, with cutting edge
technology and a strategic configuration of ~100 telescopes distributed in two
observing sites, in the northern and southern hemispheres, will reach better
sensitivity, angular and energy resolution, and broader energy coverage than
currently operational IACTs. With CTA we can probe the most extreme
environments and considerably boost our knowledge of the non-thermal Universe.Comment: Submitted as input to ASTRONET Science Vision and Infrastructure
roadmap on behalf of the CTA consortiu
First detection of VHE gamma-ray emission from TXS 1515-273, study of its X-ray variability and spectral energy distribution
We report here on the first multi-wavelength (MWL) campaign on the blazar TXS
1515-273, undertaken in 2019 and extending from radio to very-high-energy gamma
rays (VHE). Up until now, this blazar had not been the subject of any detailed
MWL observations. It has a rather hard photon index at GeV energies and was
considered a candidate extreme high-synchrotronpeaked source. MAGIC
observations resulted in the first-time detection of the source in VHE with a
statistical significance of 7.6. The average integral VHE flux of the
source is 6 1% of the Crab nebula flux above 400 GeV. X-ray coverage was
provided by Swift-XRT, XMMNewton, and NuSTAR. The long continuous X-ray
observations were separated by 9 h, both showing clear hour scale
flares. In the XMM-Newton data, both the rise and decay timescales are longer
in the soft X-ray than in the hard X-ray band, indicating the presence of a
particle cooling regime. The X-ray variability timescales were used to
constrain the size of the emission region and the strength of the magnetic
field. The data allowed us to determine the synchrotron peak frequency and
classify the source as a flaring high, but not extreme, synchrotron peaked
object. Considering the constraints and variability patterns from the X-ray
data, we model the broad-band spectral energy distribution. We applied a simple
one-zone model, which could not reproduce the radio emission and the shape of
the optical emission, and a two-component leptonic model with two interacting
components, enabling us to reproduce the emission from radio to VHE band
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