293 research outputs found
CIV and CIII] reverberation mapping of the luminous quasar PG 1247+267
So far the masses of about 50 active galactic nuclei have been measured
through the reverberation mapping technique (RM). Most measurements have been
performed for objects of moderate luminosity and redshift, based on H,
which is also used to calibrate the scaling relation which allows single-epoch
(SE) mass determination based on AGN luminosity and the width of different
emission lines. The SE mass obtained from CIV line shows a
large spread around mean values, due to complex structure and gas dynamics of
the relevant emission region. Direct RM measures of CIV exist for only 6 AGNs
of low luminosity and redshift, and only one luminous quasar (Kaspi et al
2007). We have collected since 2003 photometric and spectroscopic observations
of PG1247+267, the most luminous quasar ever analyzed for RM. We provide light
curves for the continuum and for CIV and
CIII], and measures of the reverberation time lags based on the
SPEAR method (Zu et al. 2011). The sizes of the line emission regions are in a
ratio , similar to the case of Seyfert galaxies,
indicating for the first time a similar ionization stratification in a luminous
quasar and low luminosity nuclei. Due to relatively small broad line region
size and relatively narrow line widths, we estimate a small mass and an
anomalously high Eddington ratio. We discuss the possibility that either the
shape of the emission region or an amplification of the luminosity caused by
gravitational lensing may be in part responsible of the result.Comment: 10 pagese, 6 figures, 3 tables, Accepted for publication in Ap
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
Extragalactic observatory science with the ASTRI mini-array at the Observatorio del Teide
The ASTRI Mini-Array is a next-generation system of nine imaging atmospheric Cherenkov telescopes that is going to be built at the Observatorio del Teide site. After a first phase, in which the instrument will be operated as an experiment prioritizing a schedule of primary science cases, an observatory phase is foreseen in which other significant targets will be pointed. We focus on the observational feasibility of extragalactic sources and on astrophysical processes that best complement and expand the ASTRI Mini-Array core science, presenting the most relevant examples that are at reach of detection over long-term time scales and whose observation can provide breakthrough achievements in the very-high energy extragalactic science. Such examples cover a wide range of gamma-ray emitters, including the study of AGN low states in the multi-TeV energy range, the possible detection of Seyfert galaxies with long exposures and the searches of dark matter lines above 10 TeV. Simulations of the presented objects show that the instrument performance will be competitive at multi-TeV energies with respect to current arrays of Cherenkov telescopes
Galactic observatory science with the ASTRI Mini-Array at the Observatorio del Teide
The ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) Mini-Array will be composed of nine imaging atmospheric Cherenkov telescopes at the Observatorio del Teide site. The array will be best suited for astrophysical observations in the 0.3-200 TeV range with an angular resolution of few arc-minutes and an energy resolution of 10-15%. A core-science programme in the first four years will be devoted to a limited number of key targets, addressing the most important open scientific questions in the very-high energy domain. At the same time, thanks to a wide field of view of about 10 degrees, ASTRI Mini-Array will observe many additional field sources, which will constitute the basis for the long-term observatory programme that will eventually cover all the accessible sky. In this paper, we review different astrophysical Galactic environments, e.g. pulsar wind nebulae, supernova remnants, and gamma -ray binaries, and show the results from a set of ASTRI Mini-Array simulations of some of these field sources made to highlight the expected performance of the array (even at large offset angles) and the important additional observatory science that will complement the core-science program
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