413 research outputs found
Angiopoietin 1 signalling, a marker of endothelial dysfunction in patients with coronary artery disease
The Optical Polarization and Warm Absorber in IRAS 17020+4544
We report the detection of ionized absorption in the ASCA spectrum of the
narrow-line Seyfert 1 galaxy IRAS 17020+4544. Subsequent optical
spectropolarimetry revealed high polarization increasing from 3% in the red to
5% in the blue, indicating electron or dust scattering as a likely origin. The
broad emission line H is somewhat less polarized than the continuum,
supporting a location of the polarizing material within the AGN. The Balmer
line decrement and reddened optical spectrum support the presence of a dusty
warm absorber in this object.
We compared the broad band optical polarization and ionized X-ray absorption
of a collection of Seyfert 1 and 1.5 galaxies, excluding classes of objects
that are likely to have significant neutral X-ray absorption. Warm absorber
objects are generally more likely to have high optical polarization than
objects with no detected ionized absorption. This result lends additional
support to the idea that the warm absorber is associated with dust and implies
either that dust transmission is responsible for at least part of the
polarization or that the polarization is revealed because of the dimming of the
optical spectrum. Spectropolarimetry of Seyfert 1s generally locates the
scattering material inside the narrow-line region and often close to or within
the broad line region, consistent with estimates of the location of the dusty
warm absorber.Comment: 11 pages using (AASTeX) aaspp4.sty and 3 Postscript figures. Accepted
for publication in Astrophysical Journal Letter
Is it Round? Spectropolarimetry of the Type II-P Supernova 1999em
We present the first multi-epoch spectropolarimetry of a type II plateau
supernova (SN II-P), with optical observations of SN 1999em on days 7, 40, 49,
159, and 163 after discovery. These data are used to probe the geometry of the
electron-scattering atmosphere before, during, and after the plateau phase,
which ended roughly 90 days after discovery. Weak continuum polarization with
an unchanging polarization angle (theta ~ 160 deg) is detected at all epochs,
with p ~ 0.2% on day 7, p ~ 0.3% on days 40 and 49, and p ~ 0.5% in the final
observations. Distinct polarization modulations across strong line features are
present on days 40, 49, 159, and 163. Uncorrected for interstellar polarization
(which is believed to be quite small), polarization peaks are associated with
strong P Cygni absorption troughs and nearly complete depolarization is seen
across the H-alpha emission profile. The temporal evolution of the continuum
polarization and sharp changes across lines indicate polarization intrinsic to
SN 1999em. When modeled in terms of the oblate, electron-scattering atmospheres
of Hoeflich, the observed polarization implies anasphericity of at least 7%
during the period studied. The temporal polarization increase may indicate
greater asphericity deeper into the ejecta. We discuss the implications of
asphericity on the use of type II-P supernovae as primary extragalactic
distance indicators through the expanding photosphere method (EPM). If
asphericity produces directionally dependant flux and peculiar galaxy motions
are characterized by sigma_v_rec = 300 km/s, it is shown that the agreement
between previous EPM measurements of SNe II and distances to the host galaxies
predicted by a linear Hubble law restrict mean SN II asphericity to values less
than 30% (3-sigma) during the photospheric phase.Comment: 65 pages (29 Figures, 4 Tables), Accepted for publication in the June
1, 2001 edition of ApJ. Revised statistical analysis of scatter in Hubble
diagram of previous EPM distances and the implications for mean SN II
asphericit
UV Spectropolarimetry of Narrow-line Radio Galaxies
We present the results of UV spectropolarimetry (2000 - 3000A) and far-UV
spectroscopy (1500 - 2000A) of two low-redshift narrow-line radio galaxies
(NLRGs) taken with the Faint Object Spectrograph onboard the Hubble Space
Telescope (HST). Spectropolarimetry of several NLRGs has shown that, by the
presence of broad permitted lines in polarized flux spectrum, they have hidden
quasars seen through scattered light. Imaging polarimetry has shown that NLRGs
including our targets often have large scattering regions of a few kpc to >~10
kpc scale. This has posed a problem about the nature of the scatterers in these
radio galaxies. Their polarized continuum has the spectral index similar to or
no bluer than that of quasars, which favors electrons as the dominant
scattering particles. The large scattering region size, however, favors dust
scattering, because of its higher scattering efficiency compared to electrons.
In this paper, we investigate the polarized flux spectrum over a wide
wavelength range, combining our UV data with previous optical/infrared
polarimetry data. We infer that the scattering would be often caused by opaque
dust clouds in the NLRGs and this would be a part of the reason for the
apparently grey scattering. In the high-redshift radio galaxies, these opaque
clouds could be the proto-galactic subunits inferred to be seen in the HST
images. However, we still cannot rule out the possibility of electron
scattering, which could imply the existence of a large gas mass surrounding
these radio galaxies.Comment: 25 pages, 21 figures. To appear in Ap
Polarimetry and Unification of Low-Redshift Radio Galaxies
We have made high-quality measurements of the polarization spectra of 13 FR
II radio galaxies and taken polarization images for 11 of these with the Keck
telescopes. Seven of the eight narrow-line radio galaxies (NLRG) are polarized,
and six of the seven show prominent broad Balmer lines in polarized light. The
broad lines are also weakly visible in total flux. Some of the NLRG show
bipolar regions with roughly circumferential polarization vectors, revealing a
large reflection nebula illuminated by a central source. Our observations
powerfully support the hidden quasar hypothesis for some NLRG. Classification
as NLRG, broad-line radio galaxy (BLRG), or quasar therefore depends on
orientation. However, not all objects fit into this unification scheme. Our
sample is biased towards objects known in advance to be polarized, but the
combination of our results with those of Hill, Goodrich and DePoy (1996) show
that at least 6 out of a complete, volume and flux-limited sample of 9 FR II
NLRG have broad lines, seen either in polarization or P_alpha.Comment: To appear in November 1999 Astronomical Journal. 49 pages, 13 figure
Anti-(insulin receptor) monoclonal antibody-stimulated tyrosine phosphorylation in cells transfected with human insulin receptor cDNA
The XMM-Newton serendipitous ultraviolet source survey catalogue
The XMM-Newton Serendipitous Ultraviolet Source Survey (XMM-SUSS) is a
catalogue of ultraviolet (UV) sources detected serendipitously by the Optical
Monitor (XMM-OM) on-board the XMM-Newton observatory. The catalogue contains
ultraviolet-detected sources collected from 2,417 XMM-OM observations in 1-6
broad band UV and optical filters, made between 24 February 2000 and 29 March
2007. The primary contents of the catalogue are source positions, magnitudes
and fluxes in 1 to 6 passbands, and these are accompanied by profile
diagnostics and variability statistics. The XMM-SUSS is populated by 753,578 UV
source detections above a 3 sigma signal-to-noise threshold limit which relate
to 624,049 unique objects. Taking account of substantial overlaps between
observations, the net sky area covered is 29-54 square degrees, depending on UV
filter. The magnitude distributions peak at 20.2, 20.9 and 21.2 in UVW2, UVM2
and UVW1 respectively. More than 10 per cent of sources have been visited more
than once using the same filter during XMM-Newton operation, and > 20 per cent
of sources are observed more than once per filter during an individual visit.
Consequently, the scope for science based on temporal source variability on
timescales of hours to years is broad. By comparison with other astrophysical
catalogues we test the accuracy of the source measurements and define the
nature of the serendipitous UV XMM-OM source sample. The distributions of
source colours in the UV and optical filters are shown together with the
expected loci of stars and galaxies, and indicate that sources which are
detected in multiple UV bands are predominantly star-forming galaxies and stars
of type G or earlier.Comment: Accepted for publication in MNRA
Enormous disc of cool gas surrounding the nearby powerful radio galaxy NGC 612 (PKS 0131-36)
We present the detection of an enormous disc of cool neutral hydrogen (HI)
gas surrounding the S0 galaxy NGC 612, which hosts one of the nearest powerful
radio sources (PKS 0131-36). Using the Australia Telescope Compact Array, we
detect M_HI = 1.8 x 10^9 M_sun of HI emission-line gas that is distributed in a
140 kpc wide disc-like structure along the optical disc and dust-lane of NGC
612. The bulk of the gas in the disc appears to be settled in regular rotation
with a total velocity range of 850 km/s, although asymmetries in this disc
indicate that perturbations are being exerted on part of the gas, possibly by a
number of nearby companions. The HI disc in NGC 612 suggests that the total
mass enclosed by the system is M_enc ~ 2.9 x 10^12 sin^-2(i) M_sun, implying
that this early-type galaxy contains a massive dark matter halo. We also
discuss an earlier study by Holt et al. that revealed the presence of a
prominent young stellar population at various locations throughout the disc of
NGC 612, indicating that this is a rare example of an extended radio source
that is hosted by a galaxy with a large-scale star-forming disc. In addition,
we map a faint HI bridge along a distance of 400 kpc in between NGC 612 and the
gas-rich (M_HI = 8.9 x 10^9 M_sun) barred galaxy NGC 619, indicating that
likely an interaction between both systems occurred. From the unusual amounts
of HI gas and young stars in this early-type galaxy, in combination with the
detection of a faint optical shell and the system's high infra-red luminosity,
we argue that either ongoing or past galaxy interactions or a major merger
event are a likely mechanism for the triggering of the radio source in NGC 612.
This paper is part of an ongoing study to map the large-scale neutral hydrogen
properties of nearby radio galaxies. --abridged--Comment: 13 pages, 9 figures. MNRAS in press. See
http://www.blackwell-synergy.com/doi/full/10.1111/j.1365-2966.2008.13142.x
for a full resolution versio
Chemotherapy-Response Monitoring of Breast Cancer Patients Using Quantitative Ultrasound-Based Intra-Tumour Heterogeneities
© 2017 The Author(s). Anti-cancer therapies including chemotherapy aim to induce tumour cell death. Cell death introduces alterations in cell morphology and tissue micro-structures that cause measurable changes in tissue echogenicity. This study investigated the effectiveness of quantitative ultrasound (QUS) parametric imaging to characterize intra-tumour heterogeneity and monitor the pathological response of breast cancer to chemotherapy in a large cohort of patients (n = 100). Results demonstrated that QUS imaging can non-invasively monitor pathological response and outcome of breast cancer patients to chemotherapy early following treatment initiation. Specifically, QUS biomarkers quantifying spatial heterogeneities in size, concentration and spacing of acoustic scatterers could predict treatment responses of patients with cross-validated accuracies of 82 ± 0.7%, 86 ± 0.7% and 85 ± 0.9% and areas under the receiver operating characteristic (ROC) curve of 0.75 ± 0.1, 0.80 ± 0.1 and 0.89 ± 0.1 at 1, 4 and 8 weeks after the start of treatment, respectively. The patients classified as responders and non-responders using QUS biomarkers demonstrated significantly different survivals, in good agreement with clinical and pathological endpoints. The results form a basis for using early predictive information on survival-linked patient response to facilitate adapting standard anti-cancer treatments on an individual patient basis
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