36 research outputs found
Cluster Galaxy Morphologies: The Relationship among Structural Parameters, Activity and the Environment
We use an approach to estimate galaxy morphologies based on an ellipticity
(e) vs. Bulge-to-Total ratio (B/T) plane. We have calibrated this plane by
comparing with Dressler's classifications. With the aid of our calibration, we
have classified 635 galaxies in 18 Abell clusters (0.02 < z < 0.08). Our
approach allowed us to recover the Kormendy's relation. We found that
ellipticals and Spirals are slightly brighter than S0 in R band. As S0 bulges
are brighter than spirals bulges, we believe that ram pressure is not the main
mechanism to generate S0s. In our sample, cluster radio galaxies morphologies
cover the range S0-E-cD and their bulges have absolutes magnitudes distributed
within -21 mag < M < -24.5 mag. If we believe Ferrarese & Merrit's relation,
these radio sources have 10^8-10^9 M black hole mass.Comment: Originally published in the proceedings of the conference "The
Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters", AIP
Conference Proceedings, Volume 1201 edited by Sebastian Heinz and Eric
Wilcots. This version contains slight modification
AGN Feedback in SDSS-IV MaNGA: AGNs have Suppressed Central Star Formation Rates
Despite the importance of feedback from active galactic nuclei (AGNs) in
models of galaxy evolution, observational constraints on the influence of AGN
feedback on star formation remain weak. To this end, we have compared the star
formation trends of 279 low-redshift AGN galaxies with 558 inactive control
galaxies using integral field unit spectroscopy from the SDSS-IV MaNGA survey.
With a Gaussian process-based methodology, we reconstruct nonparametric star
formation histories in spatially resolved spaxels covering the face of each
galaxy. Based on galaxy-wide star formation rates (SFRs) alone, we find no
obvious signatures of AGN feedback. However, the AGN galaxies have
significantly suppressed central (kiloparsec-scale) SFRs, lying up to a factor
of below those of the control galaxies, providing direct observational
evidence of AGN feedback suppressing star formation. The suppression of central
SFRs in the AGN galaxies began in the central regions Gyr ago
(redshift ), taking place over a few gigayears. A small subset of
the AGN galaxies were rapidly driven to quiescence shortly before being
observed (in the last Myr), potentially indicating instances of
AGN-driven feedback. More frequently, however, star formation continues in the
AGN galaxies, with suppression primarily in the central regions. This is
suggestive of a picture in which integrated (Gyr-timescale) AGN feedback can
significantly affect central star formation, but may be inefficient in driving
galaxy-wide quenching in low-redshift galaxies, instead leaving them in the
green valley.Comment: 22 pages, 15 figures. Accepted for publication in Ap
GARROTXA Cosmological Simulations of Milky Way-sized Galaxies: General Properties, Hot-gas Distribution, and Missing Baryons
We introduce a new set of simulations of Milky Way (MW)-sized galaxies using the AMR code ART + hydrodynamics in a Λ cold dark matter cosmogony. The simulation series is called GARROTXA and it follows the formation of a halo/galaxy from z = 60 to z = 0. The final virial mass of the system is ¿7.4 × 1011 M ⊙. Our results are as follows. (a) Contrary to many previous studies, the circular velocity curve shows no central peak and overall agrees with recent MW observations. (b) Other quantities, such as M\_\ast (6 × 1010 M ⊙) and R d (2.56 kpc), fall well inside the observational MW range. (c) We measure the disk-to-total ratio kinematically and find that D/T = 0.42. (d) The cold-gas fraction and star formation rate at z = 0, on the other hand, fall short of the values estimated for the MW. As a first scientific exploitation of the simulation series, we study the spatial distribution of hot X-ray luminous gas. We have found that most of this X-ray emitting gas is in a halo-like distribution accounting for an important fraction but not all of the missing baryons. An important amount of hot gas is also present in filaments. In all our models there is not a massive disk-like hot-gas distribution dominating the column density. Our analysis of hot-gas mock observations reveals that the homogeneity assumption leads to an overestimation of the total mass by factors of 3-5 or to an underestimation by factors of 0.7-0.1, depending on the used observational method. Finally, we confirm a clear correlation between the total hot-gas mass and the dark matter halo mass of galactic systems
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A Transient “Changing-look” Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data
We report the discovery of a new “changing-look” active galactic nucleus (CLAGN) event, in the quasar SDSS J162829.17+432948.5 at z = 0.2603, identified through repeat spectroscopy from the fifth Sloan Digital Sky Survey (SDSS-V). Optical photometry taken during 2020-2021 shows a dramatic dimming of Δg ≈ 1 mag, followed by a rapid recovery on a timescale of several months, with the ≲2 month period of rebrightening captured in new SDSS-V and Las Cumbres Observatory spectroscopy. This is one of the fastest CLAGN transitions observed to date. Archival observations suggest that the object experienced a much more gradual dimming over the period of 2011-2013. Our spectroscopy shows that the photometric changes were accompanied by dramatic variations in the quasar-like continuum and broad-line emission. The excellent agreement between the pre- and postdip photometric and spectroscopic appearances of the source, as well as the fact that the dimmest spectra can be reproduced by applying a single extinction law to the brighter spectral states, favor a variable line-of-sight obscuration as the driver of the observed transitions. Such an interpretation faces several theoretical challenges, and thus an alternative accretion-driven scenario cannot be excluded. The recent events observed in this quasar highlight the importance of spectroscopic monitoring of large active galactic nucleus samples on weeks-to-months timescales, which the SDSS-V is designed to achieve
A Transient "Changing-look'' Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data
We report the discovery of a new ``changing-look'' active galactic nucleus
(CLAGN) event, in the quasar SDSS J162829.17+432948.5 at z=0.2603, identified
through repeat spectroscopy from the fifth Sloan Digital Sky Survey (SDSS-V).
Optical photometry taken during 2020--2021 shows a dramatic dimming of
g1 mag, followed by a rapid recovery on a timescale of
several months, with the 2 month period of rebrightening captured
in new SDSS-V and Las Cumbres Observatory spectroscopy. This is one of the
fastest CLAGN transitions observed to date. Archival observations suggest that
the object experienced a much more gradual dimming over the period of
2011--2013. Our spectroscopy shows that the photometric changes were
accompanied by dramatic variations in the quasar-like continuum and broad-line
emission. The excellent agreement between the pre- and postdip photometric and
spectroscopic appearances of the source, as well as the fact that the dimmest
spectra can be reproduced by applying a single extinction law to the brighter
spectral states, favor a variable line-of-sight obscuration as the driver of
the observed transitions. Such an interpretation faces several theoretical
challenges, and thus an alternative accretion-driven scenario cannot be
excluded. The recent events observed in this quasar highlight the importance of
spectroscopic monitoring of large active galactic nucleus samples on
weeks-to-months timescales, which the SDSS-V is designed to achieve.Comment: Published in ApJ
The Sloan Digital Sky Survey Reverberation Mapping Project: Key Results
We present the final data from the Sloan Digital Sky Survey Reverberation
Mapping (SDSS-RM) project, a precursor to the SDSS-V Black Hole Mapper
Reverberation Mapping program. This data set includes 11-year photometric and
7-year spectroscopic light curves for 849 broad-line quasars over a redshift
range of 0.1<z<4.5 and a luminosity range of Lbol=1E44-47.5 erg/s, along with
spectral and variability measurements. We report 23, 81, 125, and 110
reverberation mapping lags (relative to optical continuum variability) for
broad Halpha, Hbeta, MgII and CIV using the SDSS-RM sample, spanning much of
the luminosity and redshift ranges of the sample. Using 30 low-redshift RM AGNs
with dynamical-modeling black hole masses, we derive a new estimate of the
average virial factor of =0.62+-0.07 for the line dispersion measured
from the RMS spectrum. The intrinsic scatter of individual virial factors is
0.31+-0.07 dex, indicating a factor of two systematic uncertainty in RM black
hole masses. Our lag measurements reveal significant R-L relations for Hbeta
and MgII at high redshift, consistent with the latest measurements based on
heterogeneous samples. While we are unable to robustly constrain the slope of
the R-L relation for CIV given the limited dynamical range in luminosity, we
found substantially larger scatter in CIV lags at fixed L1350. Using the
SDSS-RM lag sample, we derive improved single-epoch (SE) mass recipes for
Hbeta, MgII and CIV, which are consistent with their respective RM masses as
well as between the SE recipes from two different lines, over the luminosity
range probed by our sample. The new Hbeta and MgII recipes are approximately
unbiased estimators at given RM masses, but there are systematic biases in the
CIV recipe. The intrinsic scatter of SE masses around RM masses is ~0.45 dex
for Hbeta and MgII, increasing to ~0.58 dex for CIV.Comment: 33 pages. Data products available at
ftp://quasar.astro.illinois.edu/public/sdssrm/final_result