20 research outputs found
How Special Are Brightest Cluster Galaxies? The Impact of Near-Infrared Luminosities on Scaling Relations for BCGs
Using the extended J, H and K magnitudes provided by the 2MASS data archive, we consider the position of brightest cluster galaxies (BCGs) in the observed relations between inferred supermassive black hole (SMBH) mass and the host galaxy properties, as well as their position in the stellar velocity dispersion and luminosity ( ∗ − L) relation, compared to E and S0 galaxies. We find that SMBH masses (M•) derived from near-infrared (NIR) magnitudes do not exceed 3×109M⊙ and that these masses agree well with the predictions made from ∗. In the NIR, there is no evidence that BCGs leave the ∗ − L relation defined by less luminous galaxies. The higher SMBH masses predicted from V-band luminosities (M• . 1010.5M⊙) are attributed to the presence of extended envelopes around the BCGs, however, this will need to be confirmed using deeper multiwavelength imaging
The Hubble Space Telescope Advanced Camera for Surveys Coma Cluster Survey. I. Survey Objectives and Design
We describe the HST ACS Coma cluster Treasury survey, a deep twopassband imaging survey of one of the nearest rich clusters of galaxies, the Coma cluster (Abell 1656). The survey was designed to cover an area of 740 arcmin2 in regions of different density of both galaxies and intergalactic medium within the cluster. The ACS failure of January 27th 2007 leaves the survey 28% complete, with 21 ACS pointings (230 arcmin2) complete, and partial data for a further 4 pointings (44 arcmin2). Predicted survey depth for 10 detections for optimal photometry of point sources is g′ = 27.6 in the F475W filter, and IC=26.8 mag in F814 (AB magnitudes). Initial simulations with artificially injected point sources show 90% recovered at magnitude limits of g′ = 27.55 and IC = 26.65. For extended sources, the predicted 10 limits for a 1 arcsecond2 region are g′ = 25.8 mag arcsec−2 and IC = 25.0 mag arcsec−2. We highlight several motivating science goals of the survey, including study of the faint end of the cluster galaxy luminosity function, structural parameters of dwarf galaxies, stellar populations and their effect on colors and color gradients, evolution of morphological components in a dense environment, the nature of ultra compact dwarf galaxies, and globular cluster populations of cluster galaxies of a range of luminosities and types. This survey will also provide a local rich cluster benchmark for various well known global scaling relations and explore new relations pertaining to the nuclear properties of galaxies
How Special are Brightest Cluster Galaxies? The Impact of Near-Infrared Luminosities on Scaling Relations for BCGs
Using the extended J, H and K magnitudes provided by the 2MASS data archive,
we consider the position of brightest cluster galaxies (BCGs) in the observed
relations between inferred supermassive black hole (SMBH) mass and the host
galaxy properties, as well as their position in the stellar velocity dispersion
and luminosity (sigma-L) relation, compared to E and S0 galaxies. We find that
SMBH masses (M) derived from near-infrared (NIR) magnitudes do not exceed
10e9.5Msol and that these masses agree well with the predictions made from
sigma. In the NIR, there is no evidence that BCGs leave the sigma-L relation
defined by less luminous galaxies. The higher SMBH masses predicted from V-band
luminosities (M~10e10.5Msol) are attributed to the presence of extended
envelopes around the BCGs, however, this will need to be confirmed using deeper
multiwavelength imaging.Comment: 4 pages, 7 figures (4 color), uses emulateapj.cls. Replaced with ApJ
Letters Accepted version. Conclusions are unchange
The nature of the HE0450-2958 System
Magain et al. (2005) argued that the host galaxy of the quasar in HE0450-2958
is substantially under-luminous given the likely mass of its nuclear black
hole. Using kinematical information from the spectra of the quasar and the
companion galaxy, an ultra-luminous infrared galaxy, we test the hypothesis
that the black hole powering the quasar was ejected from the companion galaxy
during a merger. We find that the ejection model can be securely ruled out,
since the kick velocity required to remove the black hole from the galaxy is
greater than about 500 km/s, inconsistent with the presence of narrow emission
line gas at the same redshift as the quasar nucleus. We also show that the
quasar in HE0450-2958 has the spectral characteristics of a narrow-line Seyfert
1 galaxy and calculate a mass for its black hole that is roughly an order of
magnitude smaller than estimated by Magain et al. The predicted luminosity of
the host galaxy is then consistent with the upper limits inferred by those
authors.Comment: 5 page
Extended Warm Gas in the ULIRG Mrk273: Galactic Outflows and Tidal Debris
We present new HST ACS medium- and narrow-band images and long-slit, optical
(4000 - 7200A) spectra obtained using the Isaac Newton Telescope (INT) on La
Palma, of the merging system Mrk273. The HST observations sample the
[OIII]4959,5007 emission from the galaxy and the nearby continuum. The images
show that the morphologies of the extended continuum and the ionised gas
emission from the galaxy are decoupled, extending almost perpendicular to each
other. In particular, we detect for the first time a spectacular structure of
ionised gas in the form of filaments extending ~23 kpc to the east of the
nuclear region. The quiescent ionised gas kinematics at these locations
suggests that these filaments are tidal debris left over from a secondary
merger event that are illuminated by an AGN in the nuclear regions. The images
also reveal a complex morphology in the nuclear region of the galaxy for both
the continuum and the [OIII] emission. Kinematic disturbance, in the form of
broad (FWHM > 500 km s-1) and/or strongly shifted (abs(\DeltaV) >150 km s-1)
emission line components, is found at almost all locations within a radius of
~4 kpc to the east and west of the northern nucleus. We fit the profiles of all
the emission lines of different ionisation with a kinematic model using up to 3
Gaussian components. From these fits we derive diagnostic line ratios that are
used to investigate the ionisation mechanisms at the different locations in the
galaxy. We show that, in general, the line ratios are consistent with
photoionization by an AGN as the main ionisation mechanism. Finally, the
highest surface brightness [OIII] emission is found in a compact region that is
coincident with the so-called SE nuclear component. The compactness, kinematics
and emission line ratios of this component suggest that it is a separate
nucleus with its own AGN.Comment: Accepted for Publication in A&
Spitzer Space Telescope Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418
We present results from a fifteen-month campaign of high-cadence (~ 3 days)
mid-infrared Spitzer and optical (B and V ) monitoring of the Seyfert 1 galaxy
NGC 6418, with the objective of determining the characteristic size of the
dusty torus in this active galactic nucleus (AGN). We find that the 3.6 m
and 4.5 m flux variations lag behind those of the optical continuum by
days and days, respectively. We
report a cross-correlation time lag between the 4.5 m and 3.6 m flux
of days. The lags indicate that the dust emitting at 3.6
m and 4.5 m is located at a distance of approximately 1 light-month
(~ 0.03 pc) from the source of the AGN UV-optical continuum. The reverberation
radii are consistent with the inferred lower limit to the sublimation radius
for pure graphite grains at 1800 K, but smaller by a factor of ~ 2 than the
corresponding lower limit for silicate grains; this is similar to what has been
found for near-infrared (K-band) lags in other AGN. The 3.6 and 4.5 m
reverberation radii fall above the K-band
size-luminosity relationship by factors and ,
respectively, while the 4.5 m reverberation radius is only 27% larger than
the 3.6 m radius. This is broadly consistent with clumpy torus models, in
which individual optically thick clouds emit strongly over a broad wavelength
range.Comment: 13 pages, 9 figure
\u3cem\u3eSpitzer Space Telescope\u3c/em\u3e Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418
We present results from a 15 month campaign of high-cadence (~3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). . . .
For the remainder of the abstract, please visit:
http://dx.doi.org/10.1088/0004-637X/801/2/12
The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs
The Coma cluster, Abell 1656, was the target of a HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in early 2007, the partially-completed survey still covers approximately 50% of the core high density region in Coma. Observations were performed for twenty-five fields with a total coverage area of 274 aremin(sup 2), and extend over a wide range of cluster-centric radii (approximately 1.75 Mpe or 1 deg). The majority of the fields are located near the core region of Coma (19/25 pointings) with six additional fields in the south-west region of the cluster. In this paper we present SEXTRACTOR source catalogs generated from the processed images, including a detailed description of the methodology used for object detection and photometry, the subtraction of bright galaxies to measure faint underlying objects, and the use of simulations to assess the photometric accuracy and completeness of our catalogs. We also use simulations to perform aperture corrections for the SEXTRACTOR Kron magnitudes based only on the measured source flux and its half-light radius. We have performed photometry for 76,000 objects that consist of roughly equal numbers of extended galaxies and unresolved objects. Approximately two-thirds of all detections are brighter than F814W=26.5 mag (AB), which corresponds to the 10sigma, point-source detection limit. We estimate that Coma members are 5-10% of the source detections, including a large population of compact objects (primarily GCs, but also cEs and UCDs), and a wide variety of extended galaxies from cD galaxies to dwarf low surface brightness galaxies. The initial data release for the HST-ACS Coma Treasury program was made available to the public in August 2008. The images and catalogs described in this study relate to our second data release
The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs
The Coma cluster was the target of a HST-ACS Treasury program designed for
deep imaging in the F475W and F814W passbands. Although our survey was
interrupted by the ACS instrument failure in 2007, the partially completed
survey still covers ~50% of the core high-density region in Coma. Observations
were performed for 25 fields that extend over a wide range of cluster-centric
radii (~1.75 Mpc) with a total coverage area of 274 arcmin^2. The majority of
the fields are located near the core region of Coma (19/25 pointings) with six
additional fields in the south-west region of the cluster. In this paper we
present reprocessed images and SExtractor source catalogs for our survey
fields, including a detailed description of the methodology used for object
detection and photometry, the subtraction of bright galaxies to measure faint
underlying objects, and the use of simulations to assess the photometric
accuracy and completeness of our catalogs. We also use simulations to perform
aperture corrections for the SExtractor Kron magnitudes based only on the
measured source flux and half-light radius. We have performed photometry for
~73,000 unique objects; one-half of our detections are brighter than the
10-sigma point-source detection limit at F814W=25.8 mag (AB). The slight
majority of objects (60%) are unresolved or only marginally resolved by ACS. We
estimate that Coma members are 5-10% of all source detections, which consist of
a large population of unresolved objects (primarily GCs but also UCDs) and a
wide variety of extended galaxies from a cD galaxy to dwarf LSB galaxies. The
red sequence of Coma member galaxies has a constant slope and dispersion across
9 magnitudes (-21<M_F814W<-13). The initial data release for the HST-ACS Coma
Treasury program was made available to the public in 2008 August. The images
and catalogs described in this study relate to our second data release.Comment: Accepted for publication in ApJS. A high-resolution version is
available at http://archdev.stsci.edu/pub/hlsp/coma/release2/PaperII.pd