5,662 research outputs found
The cAMP-producing agonist beraprost inhibits human vascular smooth muscle cell migration via exchange protein directly activated by cAMP
This work was supported by the British Heart foundation (grant FS/11/23/28730). J.S.M. was funded by a British Heart Foundation PhD studentship. Funding to pay the Open Access publication charges for this article was provided by the Charities Open Access Fund (UK).Peer reviewedPublisher PD
Dust-Gas Scaling Relations and OH Abundance in the Galactic ISM
Observations of interstellar dust are often used as a proxy for total gas
column density . By comparing thermal dust data
(Release 1.2) and new dust reddening maps from Pan-STARRS 1 and 2MASS (Green et
al. 2018), with accurate (opacity-corrected) HI column densities and
newly-published OH data from the Arecibo Millennium survey and 21-SPONGE, we
confirm linear correlations between dust optical depth , reddening
and the total proton column density in the range
(130)10cm, along sightlines with no molecular gas
detections in emission. We derive an / ratio of
(9.41.6)10cmmag for purely atomic sightlines
at 5, which is 60 higher than the canonical value of
Bohlin et al. (1978). We report a 40 increase in opacity
=/, when moving from the low column
density (510cm) to moderate column
density (510cm) regime, and suggest that
this rise is due to the evolution of dust grains in the atomic ISM. Failure to
account for HI opacity can cause an additional apparent rise in ,
of the order of a further 20. We estimate molecular hydrogen column
densities from our derived linear relations, and hence
derive the OH/H abundance ratio of 110
for all molecular sightlines. Our results show no evidence of systematic trends
in OH abundance with in the range
(0.110)10cm. This suggests
that OH may be used as a reliable proxy for H in this range, which includes
sightlines with both CO-dark and CO-bright gas.Comment: The revised manuscript is accepted for publication in The
Astrophysical Journa
A revision of the X-ray absorption nature of the BALQSOs
Broad absorption line quasars (BALQSOs) are key objects for studying the
structure and emission/absorption properties of AGN. However, despite their
fundamental importance, the properties of BALQSOs are still not well
understood. In order to investigate the X-ray nature of these sources, as well
as the correlations between X-ray and rest-frame UV properties, we compile a
large sample of 88 BALQSOs observed by XMM-Newton. We performed a full X-ray
spectral analysis on a sample of 39 sources with higher X-ray spectral quality,
and an approximate HR analysis on the remaining sources. Using available
optical spectra, we calculate the BALnicity index and investigate the
dependence between this optical parameter and different X-ray properties.
Using the neutral absorption model, we found that 36% of our BALQSOs have NH
< 5x10^21 cm^-2, lower than the expected X-ray absorption for such objects.
However, when we used a physically-motivated model for the X-ray absorption in
BALQSOs, i.e. ionized absorption, \sim 90% of the objects are absorbed. The
absorption properties also suggest that LoBALs may be physically different
objects from HiBALs. In addition, we report on a correlation between the
ionized absorption column density and BAL parameters. There is evidence (at 98%
level) that the amount of X-ray absorption is correlated with the strength of
high-ionization UV absorption. This correlation, not previously reported, can
be naturally understood in virtually all BALQSO models, as driven by the total
amount of gas mass flowing towards the observer.Comment: Accepted by A&A. 12 pages, 8 figures. Added references and corrected
typo
A High-Velocity Narrow Absorption Line Outflow in the Quasar J212329.46-005052.9
We report on a variable high-velocity narrow absorption line outflow in the
redshift 2.3 quasar J2123-0050. Five distinct outflow systems are detected with
velocity shifts from -9710 to -14,050 km/s and CIV 1548,1551 line widths of
FWHM = 62-164 km/s. These data require five distinct outflow structures with
similar kinematics, physical conditions and characteristic sizes of order
0.01-0.02 pc. The most likely location is ~5 pc from the quasar. The
coordinated line variations in <0.63 yr (rest) are best explained by global
changes in the outflow ionization caused by changes in the quasar's ionizing
flux. The absence of strong X-ray absorption shows that radiative shielding is
not needed to maintain the moderate ionizations and therefore, apparently, it
is not needed to facilitate the radiative acceleration to high speeds. The
kinetic energy yield of this flow is at least two orders of magnitude too low
to be important for feedback to the host galaxy's evolution.Comment: 20 pages. In press with MNRA
Herschel-ATLAS: the far-infrared properties and star-formation rates of broad absorption line quasi-stellar objects
We have used data from the Herschel-ATLAS at 250, 350 and 500 \mu m to
determine the far-infrared (FIR) properties of 50 Broad Absorption Line Quasars
(BAL QSOs). Our sample contains 49 high-ionization BAL QSOs (HiBALs) and 1
low-ionization BAL QSO (LoBAL) which are compared against a sample of 329
non-BAL QSOs. These samples are matched over the redshift range 1.5 \leq z <
2.3 and in absolute i-band magnitude over the range -28 \leq M_{i} \leq -24. Of
these, 3 BAL QSOs (HiBALs) and 27 non-BAL QSOs are detected at the > 5 sigma
level. We calculate star-formation rates (SFR) for our individually detected
HiBAL QSOs and the non-detected LoBAL QSO as well as average SFRs for the BAL
and non-BAL QSO samples based on stacking the Herschel data. We find no
difference between the HiBAL and non-BAL QSO samples in the FIR, even when
separated based on differing BAL QSO classifications. Using Mrk 231 as a
template, the weighted mean SFR is estimated to be \approx240\pm21 M_{\odot}
yr^{-1} for the full sample, although this figure should be treated as an upper
limit if AGN-heated dust makes a contribution to the FIR emission. Despite
tentative claims in the literature, we do not find a dependence of {\sc C\,iv}
equivalent width on FIR emission, suggesting that the strength of any outflow
in these objects is not linked to their FIR output. These results strongly
suggest that BAL QSOs (more specifically HiBALs) can be accommodated within a
simple AGN unified scheme in which our line-of-sight to the nucleus intersects
outflowing material. Models in which HiBALs are caught towards the end of a
period of enhanced spheroid and black-hole growth, during which a wind
terminates the star-formation activity, are not supported by the observed FIR
properties.Comment: 11 pages, 4 figures, 4 tables. Accepted for publication in MNRA
MaGICC discs: matching observed galaxy relationships over a wide stellar mass range
We use the same physical model to simulate four galaxies that match the relation between stellar and total mass, over a mass range that includes the vast majority of disc galaxies. The resultant galaxies, part of the Making Galaxies in a Cosmological Context (MaGICC) program, also match observed relations between luminosity, rotation velocity, size, colour, star formation rate, HI mass, baryonic mass, and metallicity. Radiation from massive stars and supernova energy regulate star formation and drive outflows, balancing the complex interplay between cooling gas, star formation, large scale outflows, and recycling of gas in a manner which correctly scales with the mass of the galaxy. Outflows also play a key role in simulating galaxies with exponential surface brightness profiles, flat rotation curves and dark matter cores. Our study implies that large scale outflows are the primary driver of the dependence of disc galaxy properties on mass. We show that the amount of outflows invoked in our model is required to meet the constraints provided by observations of OVI absorption lines in the circum-galactic-media of local galaxies
微細なパターンの識別法の数値デモンストレーション(基研研究会「統計物理の展望」,研究会報告)
この論文は国立情報学研究所の電子図書館事業により電子化されました
Radio and X-ray emission from disc winds in radio-quiet quasars
It has been proposed that the radio spectra of radio-quiet quasars is
produced by free-free emission in the optically thin part of an accretion disc
wind. An important observational constraint on this model is the observed X-ray
luminosity. We investigate this constraint using a sample of PG radio-quiet
quasars for which XMM-Newton EPIC spectra are available. Comparing the
predicted and measured luminosities for 0.5, 2 and 5 keV, we conclude that all
of the studied PG quasars require a large hydrogen column density absorber,
requiring these quasars to be close to or Compton-thick. Such a large column
density can be directly excluded for PG 0050+124, for which a high-resolution
RGS spectrum exists. Further constraint on the column density for a further 19
out of the 21 studied PG quasars comes from the EPIC spectrum characteristics
such as hard X-ray power-law photon index and the equivalent width of the Fe
Kalpha line; and the small equivalent width of the C IV absorber present in UV
spectra. For 2 sources: PG 1001+054 and PG 1411+442 we cannot exclude that they
are indeed Compton-thick, and the radio and X-ray luminosity are due to a wind
originating close to the super-massive black hole. We conclude that for 20 out
of 22 PG quasars studied free-free emission from a wind emanating from the
accretion disc cannot mutually explain the observed radio and X-ray luminosity.Comment: Accepted for publication in MNRAS, 10 pages, 5 figure
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