532 research outputs found
AGN counts at 15um. XMM observations of the ELAIS-S1-5 sample
Context: The counts of galaxies and AGN in the mid infra-red (MIR) bands are
important instruments for studying their cosmological evolution. However, the
classic spectral line ratios techniques can become misleading when trying to
properly separate AGN from starbursts or even from apparently normal galaxies.
Aims: We use X-ray band observations to discriminate AGN activity in
previously classified MIR-selected starburst galaxies and to derive updated
AGN1 and (Compton thin) AGN2 counts at 15 um.
Methods: XMM observations of the ELAIS-S1 15um sample down to flux limits
~2x10^-15 erg cm^-2 s^-1 (2-10 keV band) were used. We classified as AGN all
those MIR sources with a unabsorbed 2-10 keV X-ray luminosity higher that
~10^42 erg/s.
Results: We find that at least about 13(+/-6) per cent of the previously
classified starburst galaxies harbor an AGN. According to these figures, we
provide an updated estimate of the counts of AGN1 and (Compton thin) AGN2 at 15
um. It turns out that at least 24% of the extragalactic sources brighter than
0.6 my at 15 um are AGN (~13% contribution to the extragalactic background
produced at fluxes brighter than 0.6 mJy).Comment: Accepted for publication on A&
Recommended from our members
Use of Artemisinin to Treat Mycoplasma haemolama Infection in Llamas
Mycoplasma haemolamae is associated with mild to marked anemia in stressed, immune-suppressed, and debilitated animals, and may be found in low numbers in healthy animals. The continued presence of the organism, detectable by polymerase chain reaction (PCR)-based assay, may be associated with an underlying problem, such as stress or immune-suppression that prevents the immune system from completely clearing M. haemolamae.
Treatment with tetracycline can improve anemia, and decrease bacterial numbers, but it does not clear the infection in the majority of cases. Artemisinin (quinghaosu), an herbal remedy derived from wormwood, has been shown to successfully treat malaria in humans. The purpose of this research was to test use of artemisinin to treat M. haemolamae infection in camelids.
Six llamas, negative for M. haemolamae by PCR and blood smear examination, were experimentally infected with the bacteria by transfusion of an infected alpaca‘s blood. Once the llamas were positive for M. haemolamae as detected by PCR, they were treated with 200 mg of artemisinin given twice daily for a total of 20 days (5 days of treatment followed by 5 days of no treatment for four rounds). Blood was collected every other day during the treatment cycle and weekly for one month after the treatment cycle ended. PCR, packed cell volume, plasma protein, and blood smear diagnosis were performed on these samples. Four of the llamas remained positive by PCR after one month of treatment. Two llamas were negative at the end of the month
and were immune-suppressed by dexamethasone to determine if artemisinin had cleared the M. haemolamae infection. Both llamas became positive once immune-suppressed with the corticosteroid. These results suggest that artemisinin did not effectively clear M. haemolamae infection in the six llamas
Recommended from our members
Use of Artemisinin to Treat Mycoplasma haemolama Infection in Llamas
Mycoplasma haemolamae is associated with mild to marked anemia in stressed, immune-suppressed, and debilitated animals, and may be found in low numbers in healthy animals. The continued presence of the organism, detectable by polymerase chain reaction (PCR)-based assay, may be associated with an underlying problem, such as stress or immune-suppression that prevents the immune system from completely clearing M. haemolamae.
Treatment with tetracycline can improve anemia, and decrease bacterial numbers, but it does not clear the infection in the majority of cases. Artemisinin (quinghaosu), an herbal remedy derived from wormwood, has been shown to successfully treat malaria in humans. The purpose of this research was to test use of artemisinin to treat M. haemolamae infection in camelids.
Six llamas, negative for M. haemolamae by PCR and blood smear examination, were experimentally infected with the bacteria by transfusion of an infected alpaca‘s blood. Once the llamas were positive for M. haemolamae as detected by PCR, they were treated with 200 mg of artemisinin given twice daily for a total of 20 days (5 days of treatment followed by 5 days of no treatment for four rounds). Blood was collected every other day during the treatment cycle and weekly for one month after the treatment cycle ended. PCR, packed cell volume, plasma protein, and blood smear diagnosis were performed on these samples. Four of the llamas remained positive by PCR after one month of treatment. Two llamas were negative at the end of the month
and were immune-suppressed by dexamethasone to determine if artemisinin had cleared the M. haemolamae infection. Both llamas became positive once immune-suppressed with the corticosteroid. These results suggest that artemisinin did not effectively clear M. haemolamae infection in the six llamas.
Key Words: Mycoplasma haemolamae, artemisinin, anemia, malaria, camelid
The multi-phase winds of Markarian 231: from the hot, nuclear, ultra-fast wind to the galaxy-scale, molecular outflow
We present the best sensitivity and angular resolution maps of the molecular
disk and outflow of Mrk 231, as traced by CO observations obtained with
IRAM/PdBI, and we analyze archival Chandra and NuSTAR observations. We
constrain the physical properties of both the molecular disk and outflow, the
presence of a highly-ionized ultra-fast nuclear wind, and their connection. The
molecular outflow has a size of ~1 kpc, and extends in all directions around
the nucleus, being more prominent along the south-west to north-east direction,
suggesting a wide-angle biconical geometry. The maximum projected velocity of
the outflow is nearly constant out to ~1 kpc, thus implying that the density of
the outflowing material decreases from the nucleus outwards as . This
suggests that either a large part of the gas leaves the flow during its
expansion or that the bulk of the outflow has not yet reached out to ~1 kpc,
thus implying a limit on its age of ~1 Myr. We find and erg s.
Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow
(UFO) with velocity -20000 km s, , and momentum load .We find as predicted for outflows undergoing an energy
conserving expansion. This suggests that most of the UFO kinetic energy is
transferred to mechanical energy of the kpc-scale outflow, strongly supporting
that the energy released during accretion of matter onto super-massive black
holes is the ultimate driver of giant massive outflows. We estimate a momentum
boost . The ratios and agree
with the requirements of the most popular models of AGN feedback.Comment: 16 pages, 17 figures. Accepted for publication in A&
The seven year Swift-XRT point source catalog (1SWXRT)
Swift is a multi-wavelength observatory specifically designed for gamma-ray
burst (GRB) astronomy that is operational since 2004. Swift is also a very
flexible multi-purpose facility that supports a wide range of scientific fields
such as active galactic nuclei, supernovae, cataclysmic variables, Galactic
transients, active stars and comets. The Swift X-ray Telescope (XRT) has
collected more than 150 Ms of observations in its first seven years of
operations. We present the list of all the X-ray point sources detected in XRT
imaging data taken in photon counting mode during the first seven years of
Swift operations. All these point-like sources, excluding the Gamma-Ray Bursts
(GRB), will be stored in a catalog publicly available (1SWXRT). We consider all
XRT observations with exposure time > 500 s taken in the period 2005-2011. Data
were reduced and analyzed with standard techniques and a list of detected
sources for each observation was produced. A careful visual inspection was
performed to remove extended, spurious and piled-up sources. Positions, count
rates, fluxes and the corresponding uncertainties were computed. We have
analyzed more than 35,000 XRT fields, with exposures ranging between 500 s and
100 ks, for a total exposure time of 140 Ms. The catalog includes ~ 89,000
entries, of which almost 85,000 are not affected by pile-up and are not GRBs.
Since many XRT fields were observed several times, we have a total of ~36,000
distinct celestial sources. We computed count rates in three energy bands:
0.3-10 keV (Full, or F), 0.3-3 keV (Soft, or S) and 2-10 keV (Hard, or H). Each
entry has a detection in at least one of these bands. In particular, we detect
~ 80,000, ~ 70,000 and ~ 25,500$ in the F, S and H band, respectively. Count
rates were converted into fluxes in the 0.5-10, 0.5-2 and 2-10 keV bands. Some
possible scientific uses of the catalog are also highlighted.Comment: 11 pages, 15 ps figures, accepted for publication in A&A. Abstract
shortened with respect to the original versio
The XMM-Newton survey of the ELAIS-S1 field II: optical identifications and multiwavelength catalogue of X-ray sources
We present optical identifications and a multi-band catalogue of a sample of
478 X-ray sources in the XMM and Chandra surveys of the central 0.6 deg^2 of
the ELAIS-S1 field. The optical/infrared counterpart of each X-ray source was
identified using R and IRAC 3.6 um bands. This method was complemented by the
precise positions obtained through Chandra observations. Approximately 94% of
the counterparts are detected in the R band, while the remaining are blank
fields in the optical down to R~24.5, but have a near-infrared counterpart
detected by IRAC within 6 arcsec from the XMM centroid. The multi-band
catalogue contains photometry in ten photometric bands (B to the MIPS 24 um).
We determined redshift and classification for 237 sources (~50% of the sample)
brighter than R=24. We classified 47% of the sources with spectroscopic
redshift as broad-line active galactic nuclei (BL AGNs) with z=0.1-3.5, while
sources without broad-lines are about 46% of the spectroscopic sample and are
found up to z=2.6. We identified 11 type 2 QSOs among the sources with X/O>8,
with z=0.9-2.6, high 2-10 keV luminosity (log(L2-10keV)>=43.8 erg/s) and hard
X-ray colors suggesting large absorbing columns at the rest frame (logN_H up to
23.6 cm^-2). BL AGNs show on average blue optical-to-near-infrared colors,
softer X-ray colors and X-ray-to-optical colors typical of optically selected
AGNs. Conversely, narrow-line sources show redder optical colors, harder X-ray
flux ratio and span a wider range of X-ray-to-optical colors. On average the
SEDs of high-luminosity BL AGNs resemble the power-law typical of unobscured
AGNs. The SEDs of NOT BL AGNs are dominated by the galaxy emission in the
optical/near-infrared, and show a rise in the mid-infrared which suggests the
presence of an obscured active nucleus.Comment: 15 pages, A&A accepted, affiliations correcte
Detailed Shape and Evolutionary Behavior of the X-ray Luminosity Function of Active Galactic Nuclei
We construct the rest-frame 2--10 keV intrinsic X-ray luminosity function of
Active Galactic Nuclei (AGNs) from a combination of X-ray surveys from the
all-sky Swift BAT survey to the Chandra Deep Field-South. We use ~3200 AGNs in
our analysis, which covers six orders of magnitude in flux. The inclusion of
the XMM and Chandra COSMOS data has allowed us to investigate the detailed
behavior of the XLF and evolution. In deriving our XLF, we take into account
realistic AGN spectrum templates, absorption corrections, and probability
density distributions in photometric redshift. We present an analytical
expression for the overall behavior of the XLF in terms of the
luminosity-dependent density evolution, smoothed two power-law expressions in
11 redshift shells, three-segment power-law expression of the number density
evolution in four luminosity classes, and binned XLF. We observe a sudden
flattening of the low luminosity end slope of the XLF slope at z>~0.6. Detailed
structures of the AGN downsizing have been also revealed, where the number
density curves have two clear breaks at all luminosity classes above log LX>43.
The two break structure is suggestive of two-phase AGN evolution, consisting of
major merger triggering and secular processes.Comment: 39 Pages, 9 figures. ApJ in pres
Broadband Observations of the Compton-thick Nucleus of NGC 3393
We present new NuSTAR and Chandra observations of NGC 3393, a galaxy reported
to host the smallest separation dual AGN resolved in the X-rays. While past
results suggested a 150 pc separation dual AGN, three times deeper Chandra
imaging, combined with adaptive optics and radio imaging suggest a single,
heavily obscured, radio-bright AGN. Using VLA and VLBA data, we find an AGN
with a two-sided jet rather than a dual AGN and that the hard X-ray, UV,
optical, NIR, and radio emission are all from a single point source with a
radius <0.2". We find that the previously reported dual AGN is most likely a
spurious detection resulting from the low number of X-ray counts (<160) at 6-7
keV and Gaussian smoothing of the data on scales much smaller than the PSF
(0.25" vs. 0.80" FWHM). We show that statistical noise in a single Chandra PSF
generates spurious dual peaks of the same separation (0.550.07" vs. 0.6")
and flux ratio (399% vs. 32% of counts) as the purported dual AGN. With
NuSTAR, we measure a Compton-thick source (NH=
cm) with a large torus half-opening angle, {\theta}=79 which we
postulate results from feedback from strong radio jets. This AGN shows a 2-10
keV intrinsic to observed flux ratio of 150. Using simulations, we find that
even the deepest Chandra observations would severely underestimate the
intrinsic luminosity of NGC 3393 above z>0.2, but would detect an unobscured
AGN of this luminosity out to high redshift (z=5).Comment: Accepted for publication in ApJ. 15 Figures and 4 table
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