86 research outputs found
Probing Elemental Abundances in SNR 1987A Using XMM-Newton
We report on the latest (2007 Jan) observations of supernova remnant (SNR)
1987A from the XMM-Newton mission. Since the 2003 May observations of Haberl et
al. (2006), 11 emission lines have experienced increases in flux by factors ~ 3
to 10, with the 775 eV line of O VIII showing the greatest increase; we have
observed 6 lines of Fe XVII and Fe XVIII previously unreported by XMM-Newton. A
two-shock model representing plasmas in non-equilibrium ionization is fitted to
the EPIC-pn spectra, yielding temperatures of ~ 0.4 and ~ 3 keV, as well as
elemental abundances for N, O, Ne, Mg, Si, S and Fe. We demonstrate that the
abundance ratio of N and O can be constrained to less than ~20% accuracy.
Within the same confidence interval, the same analysis suggests that the C+N+O
abundance varies from ~ 1.1 to 1.4 X 10^-4. Normalizing our obtained abundances
by the Large Magellanic Cloud (LMC) values of Hughes, Hayashi & Koyama (1998),
we find that O, Ne, Mg and Fe are under-abundant, while Si and S are
over-abundant, consistent with the findings of Aschenbach (2007). Such a result
has implications for both the single-star and binary accretion/merger models
for the progenitor of SNR 1987A. In the context of the binary merger scenario
proposed by Morris & Podsiadlowski (2006, 2007), material forming the inner,
equatorial ring was expelled after the merger, implying that either our derived
Fe abundance is inconsistent with typical LMC values or that iron is
under-abundant at the site of the progenitor star of SNR 1987A.Comment: 14 pages, 10 diagrams (2 omitted). Accepted by Ap
XMM-Newton Observation of a Distant X-ray Selected Cluster of Galaxies at z=1.26 with Possible Cluster Interaction
We report on the XMM-Newton (XMM) observation of RXJ1053.7+5735, one of the
most distant (z = 1.26) X-ray selected clusters of galaxies, which also shows
an unusual double-lobed X-ray morphology, indicative of possible
cluster-cluster interaction. The cluster was discovered during our ROSAT deep
pointings in the direction of the Lockman Hole. The XMM observations were
performed with the European Photon Imaging Camera (EPIC) during the performance
verification phase. Total effective exposure time was ~ 100 ksec. The best fit
temperature based on a simultaneous fit of spectra from the all EPIC cameras is
4.9(+1.5/-0.9) keV. Metallicity is poorly constrained even using the joint fit
of all spectra, with an upper limit on the iron abundance of 0.62 solar. Using
the best fit model parameters, we derived a bolometric luminosity of L(bol) =
3.4x10^44 h_{50}^-2 erg /s. Despite the fact that it was observed at fairly
large off-axis angle, the temperature errors are much smaller compared with
those of typical measurements based on ASCA or Beppo-Sax observations of z >
0.6 clusters, demonstrating the power of the XMM for determining the X-ray
temperature for high-z clusters. The measured temperature and luminosity show
that one can easily reach the intrinsically X-ray faint and cool cluster regime
comparable with those of z ~ 0.4 clusters observed by past satellites. The new
cluster temperature and L(bol) we have measured for RXJ1053.7+5735 is
consistent with a weak/no evolution of the L(bol) - Tx relation out to z ~ 1.3,
which lends support to a low Omega universe, although more data-points of z > 1
clusters are required for a more definitive statement. The caution has to be
also exercised in interpreting the result, because of the uncertainty
associated with the dynamical status of this cluster.Comment: Accepted for pubblication in A&A. 7 figures (One color figure is
changed to black and white.
Multiple Components of the Luminous Compact X-ray Source at the Edge of Holmberg II observed by ASCA and ROSAT
We report the results of the analysis of ASCA/ROSAT observations of the
compact luminous X-ray source found at the edge of the nearby star-forming
dwarf galaxy Holmberg II (UGC 4305).Our ASCA spectrum revealed that the X-ray
emission extends to the hard band and can be best described by a power-law with
a photon spectral index of 1.9. The ASCA spectrum does not fit with a
multi-color disk blackbody. The joint ASCA-ROSAT spectrum suggests two
components to the spectrum: the hard power-law component and a warm thermal
plasma kT~0.3[keV]. An additional absorption over that of our galaxy is
required. The wobble correction of the ROSAT HRI image has clearly unveiled the
existence of an extended component which amounts to 27+/-5% of the total X-ray
emission.
These observations indicate that there are more than one component in the
X-ray emission. The properties of the point-like component is indicative of an
accretion onto an intermediate mass blackhole, unless a beaming is taking
place. We argue that the extended component does not come from electron
scattering and/or reflection by scattered optically-thick clouds of the central
radiation. Possible explanations of this X-ray source include multiple
supernova remnants feeding an intermediate-mass blackhole. (abridged)Comment: 12 pages, 6 figures accepted to Astronomical Journa
Spectral Properties of Populations Behind the Coherence in Spitzer Near-infrared and Chandra X-Ray Backgrounds
We study the coherence of the near-infrared and X-ray background fluctuations
and the X-ray spectral properties of the sources producing it. We use data from
multiple Spitzer and Chandra surveys, including the UDS/SXDF surveys, the
Hubble Deep Field North, the EGS/AEGIS field, the Chandra Deep Field South and
the COSMOS surveys, comprising 2275 Spitzer/IRAC hours and ~16 Ms
of Chandra data collected over a total area of ~1~deg. We report an
overall 5 detection of a cross-power signal on large angular
scales 20 between the 3.6 and 4.5\mum\ and the X-ray bands, with the IR
vs [1-2] keV signal detected at 5.2. The [0.5-1] and [2-4] keV bands
are correlated with the infrared wavelengths at a 13
significance level. The hardest X-ray band ([4-7] keV) alone is not
significantly correlated with any infrared wavelengths due to poor photon and
sampling statistics. We study the X-ray SED of the cross-power signal. We find
that its shape is consistent with a variety of source populations of accreting
compact objects, such as local unabsorbed AGNs or high-z absorbed sources. We
cannot exclude that the excess fluctuations are produced by more than one
population. Because of poor statistics, the current relatively broad
photometric bands employed here do not allow distinguishing the exact nature of
these compact objects or if a fraction of the fluctuations have instead a local
origin.Comment: 14 Pages, 4 figures, Accepted by ApJ, for inquires please contact
author N. Cappellut
The SPLASH and Chandra COSMOS Legacy Survey: the Cross Power Between Near-Infrared and X-Ray Background Fluctuations
We study the source-subtracted near-infrared and X-ray background
fluctuations of the COSMOS field using data from the Spitzer SPLASH program
(1272 hours) and Chandra COSMOS Legacy Survey (4.6 Ms). The new auto
power spectra of the cosmic infrared and X-ray background fluctuations reach
maximum angular scales of 3000 and 5000, respectively. We
measure the cross power spectra between each infrared and X-ray band and
calculate the mean power above 20. We find that the soft X-ray band is
correlated with 3.6 and 4.5m at 4 significance level. The
significance between hard X-ray and the 3.6m (4.5m) band is 2.2
(3.8). The combined infrared (3.6 + 4.5m) data are
correlated with the X-ray data in soft ([0.5-2] keV), hard ([2-7] keV) and
broad ([0.5-7] keV) bands at 5.6, 4.4 and
6.6 level, respectively. We compare the new measurements with
existing models for the contributions from known populations at 7, which
are not subtracted. The model predictions are consistent with the measurements
but we cannot rule out contributions from other components, such as Direct
Collapse Black Holes (DCBH). However, the stacked cross-power spectra,
combining other available data, show excess fluctuations about an order of
magnitude on average at 4 confidence at scales within
300. By studying the X-ray SED of the cross-power signal, assuming no
significant variation from the infrared, we find that its shape is consistent
with DCBHs.Comment: 20 pages, 20 figures, 4 table
DEMON: a Proposal for a Satellite-Borne Experiment to study Dark Matter and Dark Energy
We outline a novel satellite mission concept, DEMON, aimed at advancing our
comprehension of both dark matter and dark energy, taking full advantage of two
complementary methods: weak lensing and the statistics of galaxy clusters. We
intend to carry out a 5000 sqdeg combined IR, optical and X-ray survey with
galaxies up to a redshift of z~2 in order to determine the shear correlation
function. We will also find ~100000 galaxy clusters, making it the largest
survey of this type to date. The DEMON spacecraft will comprise one IR/optical
and eight X-ray telescopes, coupled to multiple cameras operating at different
frequency bands. To a great extent, the technology employed has already been
partially tested on ongoing missions, therefore ensuring improved reliability.Comment: 12 pages, 3 figures, accepted for publication in the SPIE conference
proceeding
Massive Galaxies in COSMOS: Evolution of Black hole versus bulge mass but not versus total stellar mass over the last 9 Gyrs?
We constrain the ratio of black hole (BH) mass to total stellar mass of
type-1 AGN in the COSMOS survey at 1<z<2. For 10 AGN at mean redshift z~1.4
with both HST/ACS and HST/NICMOS imaging data we are able to compute total
stellar mass M_(*,total), based on restframe UV-to-optical host galaxy colors
which constrain mass-to-light ratios. All objects have virial BH mass-estimates
available from the COSMOS Magellan/IMACS and zCOSMOS surveys. We find zero
difference between the M_BH--M_(*,total)-relation at z~1.4 and the
M_BH--M_(*,bulge)-relation in the local Universe.
Our interpretation is: (a) If our objects were purely bulge-dominated, the
M_BH--M_(*,bulge)-relation has not evolved since z~1.4. However, (b) since we
have evidence for substantial disk components, the bulges of massive galaxies
(logM_(*,total)=11.1+-0.25 or logM_BH~8.3+-0.2) must have grown over the last 9
Gyrs predominantly by redistribution of disk- into bulge-mass. Since all
necessary stellar mass exists in the galaxy at z=1.4, no star-formation or
addition of external stellar material is required, only a redistribution e.g.
induced by minor and major merging or through disk instabilities. Merging, in
addition to redistributing mass in the galaxy, will add both BH and
stellar/bulge mass, but does not change the overall final M_BH/M_(*,bulge)
ratio.
Since the overall cosmic stellar and BH mass buildup trace each other tightly
over time, our scenario of bulge-formation in massive galaxies is independent
of any strong BH-feedback and means that the mechanism coupling BH and bulge
mass until the present is very indirect.Comment: Published in ApJL; 7 pages, 2 figures; updated to accepted version
(methods changed, results unchanged
A survey of AGN and supermassive black holes in the COSMOS Survey
The Cosmic Evolution Survey (COSMOS) is an HST/ACS imaging survey of 2 square degrees centered on RA = 10:00:28.6, Dec = + 02:12:21 (J2000). While the primary goal of the survey is to study evolution of galaxy morphology and large scale structure, an extensive multi-wavelength data set allows for a sensitive survey of AGN. Spectroscopy of optical counterparts to faint X-ray and radio sources is being carried out with the Magallen (Baade) Telescope and the ESO VLT. By achieving 80 redshift completeness down to I AB = 3, the eventual yield of AGN will be 1100 over the whole field. Early results on supermassive black holes are described. The goals of the survey include a bolometric census of AGN down to moderate luminosities, the cosmic evolution and fueling history of the central engines, and a study of AGN environments on scales ranging from the host galaxy to clusters and supercluster
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