228 research outputs found
Broad Line Region Physical Conditions along the Quasar Eigenvector 1 Sequence
[Abridged] We compare broad emission line profiles and estimate line ratios
for all major emission lines between Ly-alpha and H-beta in a sample of six
quasars. The sources were chosen with two criteria in mind: the existence of
high quality optical and UV spectra as well as the possibility to sample the
spectroscopic diversity in the 4D Eigenvector 1 context . In the latter sense
each source occupies a region (bin) in the FWHM(H-beta) vs. optical FeII
strength plane that is significantly different from the others. High S/N H-beta
emission line profiles are used as templates for modeling the other lines
(Ly-alpha, CIV 1549, HeII 1640, Al III 1860, Si III] 1892, and Mg II 2800). We
can adequately model all broad lines assuming the existence of three components
distinguished by blueshifted, unshifted and redshifted centroids (indicated as
blue, broad and very broad component respectively). The broad component (high
electron density, low ionization parameter; high column density) is present in
almost all type-1 quasars and therefore corresponds most closely to the
classical broad line emitting region (the reverberating component). The blue
component emission (lower electron density; high ionization; low column
density) arises in less optically thick gas; it is often thought to arise in an
accretion disk wind. The least understood component involves the very broad
component (high ionization and large column density). It is perhaps the most
distinguishing characteristic of quasars with FWHM H-beta > 4000 km/s that
belong to the so-called Population B of our 4DE1 space. Population A quasars
(FWHM H-beta < 4000 km/s) are dominated by broad component emission in H-beta
and blue component emission in CIV 1549 and other high ionization lines. 4DE1
appears to be the most useful current context for revealing and unifying
spectral diversity in type-1 quasars.Comment: 7 Tables, 5 Figures; accepted for publication in Monthly Notices of
the Royal Astronomical Societ
H-alpha variability of the recurrent nova T Coronae Borealis
We analyze H-alpha observations of the recurrent nova T CrB obtained during
the last decade. For the first time the H-alpha emission profile is analyzed
after subtraction of the red giant contribution. Based on our new radial
velocity measurements of the H-alpha emission line we estimate the component
masses of T CrB. It is found that the hot component is most likely a massive
white dwarf. We estimate the inclination and the component masses to be i~67
deg, Mwd = 1.37 +/-0.13 Msun and Msec=1.12 +/-0.23 Msun, respectively. The
radial velocity of the central dip in the H-alpha profile changes nearly in
phase with that of the red giant's absorption lines. This suggests that the dip
is most likely produced by absorption in the giant's wind.
Our observations cover an interval when the H-alpha and the U-band flux vary
by a factor of ~6, while the variability in B and V is much smaller. Based on
our observations, and archival ultraviolet and optical data we show that the
optical, ultraviolet and H-alpha fluxes strongly correlate. We argue that the
presence of an accretion disc can account for most of the observed properties
of T CrB.Comment: 8 pages, 6 EPS figures, to appear in A&
Average UV Quasar Spectra in the Context of Eigenvector 1: A Baldwin Effect Governed by Eddington Ratio?
We present composite UV spectra for low redshift Type 1 AGN binned to exploit
the information content of the Eigenvector 1 (E1) parameter space. Composite
spectra allow a decomposition of the CIV1549 line profile - one of the
strongest high-ionization lines. The simplest CIV decomposition into narrow
(NLR), broad (BLR) and very broad (VBLR) components suggests that different
components have an analog in Hb with two major exceptions. VBLR emission is
seen only in population B (FWHM(Hb)>4000 km/s) sources. A blue
shifted/asymmetric BLR component is seen only in pop. A (FWHM(Hb)<4000 km/s)
HIL such as CIV. The blueshifted component is thought to arise in a wind or
outflow. Our analysis suggests that such a wind can only be produced in pop. A
(almost all radio-quiet) sources where the accretion rate is relatively high.
Comparison between broad UV lines in radio-loud (RL) and radio-quiet (RQ)
sources shows few significant differences. Clear evidence is found for a narrow
CIV component in most radio-loud sources. We find also some indirect
indications that the black hole (BH) spin, rather than BH mass or accretion
rate is a key trigger in determining whether an object will be RL or RQ. We
find a ten-fold decrease in EW CIV with Eddington ratio (decreasing from ~1 to
\~0.01) while NV shows no change. These trends suggest a luminosity-independent
"Baldwin effect" where the physical driver may be the Eddington ratio.Comment: 39 pages, 6 figures. To appear in Ap
The Circum-Galactic Environment of Bright IRAS Galaxies
This paper studies systematically, for the first time, the circumgalactic
environment of bright IRAS galaxies as defined by Soifer et al. (1989). While
the role of gravitational interaction for luminous and ultraluminous IRAS
galaxies has been well established by various studies, the situation is by far
more obscure in the IR luminosity range of the bright IRAS sample, 10^{10}Lsol
< Lfir < 10^{11} Lsol. To easily identify nearby companion galaxies, the bright
IRAS sample was restricted to 87 objects with redshift range 0.008 < z < 0.018
and galactic latitude > 30^{o}. A control sample, selected from the Center for
Astrophysics redshift survey catalogue, includes 90 objects matching the Bright
IRAS sample for distribution of isophotal diameter, redshift, and morphological
type. From a search of nearby companion galaxies within 250 Kpc on the
second-generation Digitized Sky Survey (DSS-II), we found that the
circumgalactic environment of the Bright IRAS galaxies contains more large
companions than the galaxies in the optically selected control sample, and is
similar to that of Seyfert 2 galaxies. We found a weak correlation over a wide
range of far IR luminosity (10^9 Lsol < Lfir < 10^{12.5}Lsol) between projected
separation and Lfir, which confirms a very close relationship between star
formation rate of a galaxy and the strength of gravitational perturbations. We
also find that the far IR colors depend on whether a source is isolated or
interacting. Finally, we discuss the intrinsic difference and evolution
expectations for the bright IRAS galaxies and the control sample, as well as
the relationship between starbursting and active galaxies.Comment: 10 pages, 5 figs, 2 tables. Accepted for publication in Ap
Average Quasar Spectra in the Context of Eigenvector 1
[LaTeX removed] Recent work has shown that it is possible to systematize
quasar spectral diversity in a parameter space called ``Eigenvector 1'' (E1).
We present median AGN spectra for fixed regions of the E1 (optical) parameter
space (FWHM(H-beta) vs. equivalent width ratio RFE=W(FeII4570)/W(H-beta).
Comparison of the median spectra for different regions show considerable
differences. We suggest that an E1-driven approach to median/average spectra
emphasizes significant differences between AGN, and offers more insights into
AGN physics and dynamics than a single population median/average derived from a
large and heterogeneous sample of sources. We find that the H-beta broad
component line profile changes in shape along the E1 sequence both in average
centroid shift and asymmetry. While objects with FWHM(H-beta)< 4000 km/s are
well fitted by a Lorentz function, AGN with FWHM(H-beta)> 4000 km/s are well
fitted if two broad line components are used: a broad (the "classical" broad
line component) and a very broad/redshifted component.Comment: 1 table + 3 figures, accepted for publication in ApJ
Preterm birth after loop electrosurgical excision procedure (LEEP). how cone features and microbiota could influence the pregnancy outcome
OBJECTIVE:
In the last years, the mean age of women who underwent cervical treatment for high-grade cervical intraepithelial neoplasia (CIN 2-3) is similar to the age of women having their first pregnancy. The aim of this study was to evaluate the risk of preterm birth in subsequent pregnancies after loop electrosurgical excision procedure (LEEP).
PATIENTS AND METHODS:
From January 2013 to January 2016 the study identified a total of 1435 women, nulliparous, who underwent LEEP for CIN 2-3, and who wished to have their first pregnancy. Before surgery, the lengths of the cervix were calculated by transvaginal sonography. After the treatment, the dimension of the removed tissue was evaluated. During the pregnancy, all women carried out periodic transvaginal sonography and vaginal-cervical swabs.
RESULTS:
The average age of patients was 31.96±5.24 years; the interval between the surgical procedure and pregnancy was 12.04±4.67 months; the gestational age at births was 37.53±2.91 weeks. The first vaginal and cervical swab performed during pregnancy was negative in 81.8% of patients. The most prevalent infections were related to C. Albicans, G. Vaginalis, and Group B Streptococcus (GBS). The rate of preterm delivery was significantly higher in women with a minor cervical length.
CONCLUSIONS:
The length and the volume of cervical tissue excised have been shown to be directly related to the risk for preterm birth. Furthermore, vaginal infections and their persistence during pregnancy in women with a history of LEEP may be associated with an increased risk for preterm birth, compared with women with no history of LEEP
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