30 research outputs found
Disturbed Fossil Group Galaxy NGC 1132
We have analyzed the Chandra archival data of NGC 1132, a well-known fossil
group, i.e. a system expected to be old and relaxed long after the giant
elliptical galaxy assembly. Instead, the Chandra data reveal that the hot gas
morphology is disturbed and asymmetrical, with a cold front following a
possible bow shock. We discuss possible origins of the disturbed hot halo,
including sloshing by a nearby object, merger, ram pressure by external hotter
gas and nuclear outburst. We consider that the first two mechanisms are likely
explanations for the disturbed hot halo, with a slight preference for a minor
merger with a low impact parameter because of the match with simulations and
previous optical observations. In this case, NGC 1132 may be a rare example of
unusual late mergers seen in recent simulations. Regardless of the origin of
the disturbed hot halo, the paradigm of the fossil system needs to be
reconsidered.Comment: 16 pages, 6 figures, accepted for publication in Ap
Chandra Early-Type Galaxy Atlas
The hot ISM in early type galaxies (ETGs) plays a crucial role in
understanding their formation and evolution. The structural features of the hot
gas identified by Chandra observations point to key evolutionary mechanisms,
(e.g., AGN and stellar feedback, merging history). In our Chandra Galaxy Atlas
(CGA) project, taking full advantage of the Chandra capabilities, we
systematically analyzed the archival Chandra data of 70 ETGs and produced
uniform data products for the hot gas properties. The primary data products are
spatially resolved 2D spectral maps of the hot gas from individual galaxies. We
emphasize that new features can be identified in the spectral maps which are
not readily visible in the surface brightness maps. The high-level images can
be viewed at the dedicated CGA website, and the CGA data products can be
downloaded to compare with data at other wavelengths and to perform further
analyses. Utilizing our data products, we address a few focused science topics.Comment: 52 pages, 9 figures, accepted in ApJ Supp
Probing the accretion disk and central engine structure of NGC4258 with Suzaku and XMM-Newton observations
[abridged] We present an X-ray study of the low-luminosity active galactic
nucleus (AGN) in NGC4258 using data from Suzaku, XMM-Newton, and the Swift/BAT
survey. We find that signatures of X-ray reprocessing by cold gas are very weak
in the spectrum of this Seyfert-2 galaxy; a weak, narrow fluorescent-Kalpha
emission line of cold iron is robustly detected in both the Suzaku and
XMM-Newton spectra but at a level much below that of most other Seyfert-2
galaxies. We conclude that the circumnuclear environment of this AGN is very
"clean" and lacks the Compton-thick obscuring torus of unified Seyfert schemes.
From the narrowness of the iron line, together with evidence for line flux
variability between the Suzaku and XMM-Newton observations, we constrain the
line emitting region to be between and from
the black hole. We show that the observed properties of the iron line can be
explained if the line originates from the surface layers of a warped accretion
disk. In particular, we present explicit calculations of the expected iron line
from a disk warped by Lens-Thirring precession from a misaligned central black
hole. Finally, the Suzaku data reveal clear evidence for large amplitude
2-10keV variability on timescales of 50ksec as well as smaller amplitude flares
on timescales as short as 5-10ksec. If associated with accretion disk
processes, such rapid variability requires an origin in the innermost regions
of the disk ( or less).Comment: 10 pages, 6 figures. Accepted for publication in the Astrophysical
Journa
Symptom Monitoring With Patient-Reported Outcomes During Routine Cancer Treatment: A Randomized Controlled Trial
There is growing interest to enhance symptom monitoring during routine cancer care using patient-reported outcomes, but evidence of impact on clinical outcomes is limited
Chandra Galaxy Atals - Global Hot Gas Properties
The hot gas in early type galaxies (ETGs) plays a crucial role in understanding their formation and evolution. As the hot gas is often extended to the outskirts beyond the optical size, the large scale structural features identified by Chandra (including jets, cavities, cold fronts, filaments and tails) point to key evolutionary mechanisms, e.g., AGN feedback, merging history, accretion/stripping and star formation and its quenching. In our new project, the Chandra Galaxy Atlas, we systematically analyze the archival Chandra data of ~100 ETGs to study the hot ISM. Using uniformly derived data products with spatially resolved spectral information, we will present gas morphology, scaling relations and X-ray based mass profiles and address their implications
X-ray Mass Profiles from Chandra Galaxy Atlas
We present preliminary results of a Chandra/XMM-Newton joint analysis on a sample of three Early Type Galaxies (ETGs, namely NGC4649, NGC4636 and NGC5846). X-ray observations of the hot ISM is used to measure the total enclosed mass assuming hydrostatic equilibrium, and compasion with mass distributions obtained through optical kinematics data of globular clusters and planetary nebulae yields informations about disturbances in the ISM distribution due to nuclear activity, merging history, etc. Our analysis makes use of the Chandra Galaxy Atlas (CGA) data products - exploiting the unmatched spatial resolution of the ACIS detectors to reveal fine ISM features and disturbances in the inner galactic regions - and XMM-Newton data - relying on the large field of view of EPIC detector to extend the mass profiles to larger radii. We then measured the mass profiles in various pie sectors to separate different gas features (e.g., discontinuity and extended tail) and compared them with GCs/PNe based mass profiles. The X-ray mass profiles of NGC4649 show a generally relaxed morphology and, in agreement with previous analysis, the comparison with the optical mass profiles shows a significant deviations on parsec scale likely due to non-thermal pressure linked to nuclear activity. In significantly disturbed cases (NGC4648 and NGC5846) where we found discontinuities and extended tails, we found that the mass profiles are over-estimated toward the compressed discontinuity and under-estimated toward the extended tails, similar to inflow and outflow cases. These preliminary results are promising toward an extended analysis of the whole CGA sample in order to study the distribution of gas temperature and metal abundances in the ISM, and to investigate scaling relations between ETG global quantities like ISM temperature, luminosity and total mass
The Chandra COSMOS Survey, I: Overview and Point Source Catalog
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra} program
that has imaged the central 0.5 sq.deg of the COSMOS field (centered at 10h,
+02deg) with an effective exposure of ~160ksec, and an outer 0.4sq.deg. area
with an effective exposure of ~80ksec. The limiting source detection depths are
1.9e-16 erg cm(-2) s(-1) in the Soft (0.5-2 keV) band, 7.3e(-16) erg cm^-2 s^-1
in the Hard (2-10 keV) band, and 5.7e(-16) erg cm(-2) s(-1) in the Full (0.5-10
keV) band. Here we describe the strategy, design and execution of the C-COSMOS
survey, and present the catalog of 1761 point sources detected at a probability
of being spurious of <2e(-5) (1655 in the Full, 1340 in the Soft, and 1017 in
the Hard bands). By using a grid of 36 heavily (~50%) overlapping pointing
positions with the ACIS-I imager, a remarkably uniform (to 12%) exposure across
the inner 0.5 sq.deg field was obtained, leading to a sharply defined lower
flux limit. The widely different PSFs obtained in each exposure at each point
in the field required a novel source detection method, because of the
overlapping tiling strategy, which is described in a companion paper. (Puccetti
et al. Paper II). This method produced reliable sources down to a 7-12 counts,
as verified by the resulting logN-logS curve, with sub-arcsecond positions,
enabling optical and infrared identifications of virtually all sources, as
reported in a second companion paper (Civano et al. Paper III). The full
catalog is described here in detail, and is available on-line.Comment: Revised to omit egregious bold facing and fix missing ',' in author
lis
Temperature profiles of hot gas in early-type galaxies
Using the data products of the Chandra Galaxy Atlas (Kim et al. 2019a), we
have investigated the radial profiles of the hot gas temperature in 60 early
type galaxies. Considering the characteristic temperature and radius of the
peak, dip, and break (when scaled by the gas temperature and virial radius of
each galaxy), we propose a universal temperature profile of the hot halo in
ETGs. In this scheme, the hot gas temperature peaks at RMAX = 35 +/- 25 kpc (or
~0.04 RVIR) and declines both inward and outward. The temperature dips (or
breaks) at RMIN (or RBREAK) = 3 - 5 kpc (or ~0.006 RVIR). The mean slope
between RMIN (RBREAK) and RMAX is 0.3 +/- 0.1. Allowing for selection effects
and observational limits, we find that the universal temperature profile can
describe the temperature profiles of 72% (possibly up to 82%) of our ETG
sample. The remaining ETGs (18%) with irregular or monotonically declining
profiles do not fit the universal profile and require another explanation. The
temperature gradient inside RMIN (RBREAK) varies widely, indicating different
degrees of additional heating at small radii. Investigating the nature of the
hot core (HC with a negative gradient inside RMIN), we find that HC is most
clearly visible in small galaxies. Searching for potential clues associated
with stellar, AGN feedback, and gravitational heating, we find that HC may be
related to recent star formation. But we see no clear evidence that AGN
feedback and gravitational heating play any significant role for HC.Comment: 36 pages, 11 figures, accepted or publication in MNRA