145 research outputs found
Quasars: from the Physics of Line Formation to Cosmology
Quasars accreting matter at very high rates (known as extreme Population A
[xA] or super-Eddington accreting massive black holes) provide a new class of
distance indicators covering cosmic epochs from the present-day Universe up to
less than 1 Gyr from the Big Bang. The very high accretion rate makes it
possible that massive black holes hosted in xA quasars radiate at a stable,
extreme luminosity-to-mass ratio. This in turns translates into stable physical
and dynamical conditions of the mildly ionized gas in the quasar low-ionization
line emitting region. In this contribution, we analyze the main optical and UV
spectral properties of extreme Population A quasars that make them easily
identifiable in large spectroscopic surveys at low-z (z < 1) and intermediate-z
(2 < z < 2.6), and the physical conditions that are derived for the formation
of their emission lines. Ultimately, the analysis supports the possibility of
identifying a virial broadening estimator from low-ionization line widths, and
the conceptual validity of the redshift-independent luminosity estimates based
on virial broadening for a known luminosity-to-mass ratio.Comment: 13 pages, 5 figures. Invited lecture at SPIG 2018, Belgrade. To
appear in Ato
Black hole mass estimates in quasars - A comparative analysis of high- and low-ionization lines
The inter-line comparison between high- and low-ionization emission lines has
yielded a wealth of information on the quasar broad line region (BLR) structure
and dynamics, including perhaps the earliest unambiguous evidence in favor of a
disk + wind structure in radio-quiet quasars. We carried out an analysis of the
CIV 1549 and Hbeta line profiles of 28 Hamburg-ESO high luminosity quasars and
of 48 low-z, low luminosity sources in order to test whether the
high-ionization line CIV 1549 width could be correlated with Hbeta and be used
as a virial broadening estimator. We analyze intermediate- to high-S/N,
moderate resolution optical and NIR spectra covering the redshifted CIV and
H over a broad range of luminosity log L ~ 44 - 48.5 [erg/s] and
redshift (0 - 3), following an approach based on the quasar main sequence. The
present analysis indicates that the line width of CIV 1549 is not immediately
offering a virial broadening estimator equivalent to H. At the same time
a virialized part of the BLR appears to be preserved even at the highest
luminosities. We suggest a correction to FWHM(CIV) for Eddington ratio (using
the CIV blueshift as a proxy) and luminosity effects that can be applied over
more than four dex in luminosity. Great care should be used in estimating
high-L black hole masses from CIV 1549 line width. However, once corrected
FWHM(CIV) values are used, a CIV-based scaling law can yield unbiased MBH
values with respect to the ones based on H with sample standard
deviation ~ 0.3 dex.Comment: 43 pages, 15 Figures, submitted to A&
Donovanosis en mujeres indígenas
La donovanosis es una rara infección causada por la bacteriaCalymmatobacteriumgranulomatisque produce importantes lesiones ulcero-granulomatosas, preferentemente en la zonaanogenital.Considerada como enfermedad de trasmisión sexual, no es ésta la única vía detrasmisión, siendo también importantes las condiciones higiénicas, socioeconómicas y ambientalesen su etiopatogenia.Afecta áreas tropicales de varios continentes, incluido el americano, donde hayseries descriptas en varios países. En el Paraguay ha sido poco reportada, por lo que esta serie decuatro pacientes mujeres, jóvenes, indígenas de varias parcialidades, con lesiones exuberantes enzona anogenital, de larga evolución, tres de ellas embarazadas y dos con extensión a órganosinternos, es importante. El objetivo de este trabajo es llamar la atención sobre un problema de granmorbilidad y que exige mejorar la cobertura de salud y condiciones de vida de estas comunidadesindígenas
Narrow-line Seyfert 1s: what is wrong in a name?
Narrow-line Seyfert 1s (NLSy1s) are an ill-defined class. Work done over the
past 20 years as well as recent analyses show a continuity in properties (e.g.,
Balmer line profiles, blueshifts of high-ionization lines) between sources with
FWHM above and below 2000 km/s, the defining boundary of NLSy1s. This finding
alone suggests that comparisons between samples of NLSy1s and rest of
broad-line AGNs are most likely biased. NLSy1s can be properly contextualized
by their location on the quasar main sequence originally defined by Sulentic et
al 2000. At one end, NLSy1s encompass sources with strong FeII emission and
associated with high Eddington ratio that hold the promise of becoming useful
distance indicators; at the other end, at least some of them are sources with
broad profiles seen face-on. Any rigid FWHM limit gives rise to some physical
ambiguity, as the FWHM of low-ionization lines depends in a complex way on
mass, Eddington ratio, orientation, and luminosity. In addition, if the scaling
derived from luminosity and virial dynamics applies to the broad line regions,
NLSy1s at luminosity higher than 1E47 erg/s become physically impossible.
Therefore, in a broader context, a proper subdivision of two distinct classes
of AGNs and quasars may be achieved by the distinction between Pop. A and B
with boundary at = 4000 km/s in samples at z < 1, or on the basis of
spectrophotometric properties which may ultimately be related to differences in
accretion modes if high-luminosity quasars are considered.Comment: Contribution presented at the meeting Revisiting narrow-line Seyfert
1 galaxies and their place in the Universe, held at the Padova Botanical
Garden, Italy, on 9-13 April 201
A main sequence for quasars
The last 25 years saw a major step forward in the analysis of optical and UV
spectroscopic data of large quasar samples. Multivariate statistical approaches
have led to the definition of systematic trends in observational properties
that are the basis of physical and dynamical modeling of quasar structure. We
discuss the empirical correlates of the so-called "main sequence" associated
with the quasar Eigenvector 1, its governing physical parameters and several
implications on our view of the quasar structure, as well as some luminosity
effects associated with the virialized component of the line emitting regions.
We also briefly discuss quasars in a segment of the main sequence that includes
the strongest FeII emitters. These sources show a small dispersion around a
well-defined Eddington ratio value, a property which makes them potential
Eddington standard candles.Comment: Invited talk presented at the Padova Conference on "Quasars at all
cosmic epochs"; to appear in Frontiers of Astrophysics and Space Scienc
Dark energy constraints from quasar observations
Recent measurements of the parameters of the Concordance Cosmology Model
(CDM) done in the low-redshift Universe with Supernovae Ia/Cepheids,
and in the distant Universe done with Cosmic Microwave Background (CMB) imply
different values for the Hubble constant (67.4 0.5 km s Mpc
from Planck vs 74.03 1.42 km s Mpc, Riess et al. 2019).
This Hubble constant tension implies that either the systematic errors are
underestimated, or the CDM does not represent well the observed
expansion of the Universe. Since quasars - active galactic nuclei - can be
observed in the nearby Universe up to redshift z 7.5, they are suitable
to estimate the cosmological properties in a large redshift range. Our group
develops two methods based on the observations of quasars in the late Universe
up to redshift z4.5, with the objective to determine the expansion rate
of the Universe. These methods do not yet provide an independent measurement of
the Hubble constant since they do not have firm absolute calibration but they
allow to test the CDM model, and so far no departures from this model
were found.Comment: 6 pages, 2 figures, contribution to the Proceedings of the 100 years
of the Polish Physical Society Congress, 16-18 October 2020, Warsaw, Poland.
http://info.ifpan.edu.pl/APP
Modelo Multifractal Aplicado al Riego
We define the binomial multifractal distribution as an expression of a law of small numbers. We studied a form of evaluation or design of a distribution system in an irrigation district by determining its conduction capacity with the desired flexibility knowing the following parameters: flow, frequency, and irrigation time. The method consists of the approximation of the binomial distribution through the Gaussian, an inverse relation of probability, two estimations of Gaussian parameters, and the application of the multifractal distribution. We present the mathematical reformulation of Boltzmann relation in the statistical mechanics, which gives origin to the multifractal model. In particular, we illustrate its application in the problems of irrigation, pointing out that it is also possible to apply it to multifractal models: variogram, exponential, gamma, and Gaussian.Definimos la distribución multifractal binomial, como expresión de una ley de los pequeños números. Estudiamos una forma de evaluación o de diseño de un sistema de distribución en un distrito de riego, al determinar su capacidad de conducción con la flexibilidad deseada, conociendo los parámetros de gasto, frecuencia y tiempo de riego. El método es la aproximación de la distribución binomial por la Gaussiana, una relación inversa de probabilidad, dos estimaciones de parámetros Gaussianos, y la aplicación de la distribución multifractal. Presentamos la reformulación matemática de la relación de Boltzmann en la mecánica estadística, que da origen al modelo multifractal. En particular, ilustramos su aplicación en el problema del riego. Pero también es posible aplicarlo a los modelos multifractales: variograma, exponencial, gama, y Gaussiano
- …