649 research outputs found
Lynch syndrome: still not a familiar picture
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Germ line mutations in mismatch repair genes underlie Lynch syndrome and predispose carriers for colorectal carcinoma and malignancies in many other organ systems. Case presentation: A large Lynch syndrome family with 15 affected family members and involvement in 7 organs is reported. It illustrates a lack of awareness and knowledge about this hereditary tumor syndrome among doctors as well as patients. None of the described family members underwent presymptomatic screening on the basis of the family history. Conclusion: Hereditary features, like young age at diagnosis, multiple tumors in multiple organs and a positive family history, should lead to timely referral of suspected cases for genetic counseling and diagnostics. For Lynch syndrome, these features can be found in the Amsterdam and Bethesda criteria. Subsequently, early identification of mutation carriers might have diminished, at least in part, the high and early morbidity and mortality observed in this family. Background Colorectal carcinoma (CRC) is an important cause of cancer-relate
[OII] Emission, Eigenvector 1 and Orientation in Radio-quiet Quasars
We present supportive evidence that the Boroson and Green eigenvector 1 is
not driven by source orientation. Until recently it was generally accepted that
eigenvector 1 does not depend on orientation as it strongly correlates with
[OIII]5007 emission, thought to be an isotropic property. However, recent
studies of radio-loud AGN have questioned the isotropy of [OIII] emission and
concluded that [OII]3727 emission is isotropic. In this paper we investigate
the relation between eigenvector 1 and [OII] emission in radio-quiet BQS
(Bright Quasar Survey) quasars, and readdress the issue of orientation as the
driver of eigenvector 1. We find significant correlations between eigenvector 1
and orientation independent [OII] emission, which implies that orientation does
not drive eigenvector 1. The luminosities and equivalent widths of [OIII] and
[OII] correlate with one another, and the range in luminosities and equivalent
widths is similar. This suggests that the radio-quiet BQS quasars are largely
free of orientation dependent dust effects and ionization dependent effects in
the narrow-line region. We also conclude that neither the [OIII] emission nor
the [OII]/[OIII] ratio are dependent on orientation in our radio-quiet BQS
quasar sample, contrary to recent results found for radio-loud quasars.Comment: 24 pages, 12 figures, accepted for publication in Ap
On the Nature of Soft X-ray Weak Quasi-Stellar Objects
Recent studies of QSOs with ROSAT suggest the existence of a significant
population of Soft X-ray Weak QSOs (SXW QSOs) where the soft X-ray flux is ~
10-30 times smaller than in typical QSOs. As a first step in a systematic study
of these objects, we establish a well-defined sample of SXW QSOs which includes
all alpha_ox<=-2 QSOs from the Boroson & Green (1992) sample of 87 BQS QSOs.
SXW QSOs comprise about 11% of this optically selected QSO sample. From an
analysis of CIV absorption in the 55 BG92 QSOs with available CIV data, we find
a remarkably strong correlation between alpha_ox and the CIV absorption
equivalent width. This correlation suggests that absorption is the primary
cause of soft X-ray weakness in QSOs, and it reveals a continuum of absorption
properties connecting unabsorbed QSOs, X-ray warm absorber QSOs, SXW QSOs and
BAL QSOs. From a practical point of view, our correlation demonstrates that
selection by soft X-ray weakness is an effective (>=80% successful) and
observationally inexpensive way to find low-redshift QSOs with strong and
interesting ultraviolet absorption. We have also identified several notable
differences between the optical emission-line properties of SXW QSOs and those
of the other BG92 QSOs. SXW QSOs show systematically low [O III] luminosities
as well as distinctive H-beta profiles. They tend to lie toward the weak-[O
III] end of BG92 eigenvector 1, as do many low-ionization BAL QSOs. Unabsorbed
Seyferts and QSOs with similar values of eigenvector 1 have been suggested to
have extreme values of a primary physical parameter, perhaps mass accretion
rate relative to the Eddington rate (M-dot/M-dot_{Edd}). If these suggestions
are correct, it is likely that SXW QSOs also tend to have generally high values
of (M-dot/M-dot_{Edd}). (Abridged)Comment: 34 pages, ApJ accepted, also available from
http://www.astro.psu.edu/users/niel/papers/papers.htm
Von Hippel-Lindau Disease
A germline mutation in the Von-Hippel Lindau (VHL) gene predisposes carriers to development of abundantly vascularised tumours in the retina, cerebellum, spine, kidney, adrenal gland and pancreas. Most VHL patients die from the consequences of cerebellar haemangioblastoma or renal cell carcinoma. The VHL gene is a tumour suppressor gene and is involved in angiogenesis by regulation of the activity of hypoxia-inducible factor 1-α (HIF1-α). Clinical diagnosis of VHL can be confirmed by molecular genetic analysis of the VHL gene, which is informative in virtually all VHL families. A patient with (suspicion for) VHL is an indication for genetic counselling and periodical examination
The Host Galaxy and The Extended Emission-Line Region of The Radio Galaxy 3C 79
We present extensive ground-based spectroscopy and HST imaging of 3C79, an FR
II radio galaxy associated with a luminous extended emission-line region
(EELR). Surface brightness modeling of an emission-line-free HST R-band image
reveals that the host galaxy is a massive elliptical with a compact companion
0.8" away and 4 magnitudes fainter. The host galaxy spectrum is best described
by an intermediate-age (1.3 Gyr) stellar population (4% by mass), superimposed
on a 10 Gyr old population and a power law (\alpha_{\lambda} = -1.8); the
stellar populations are consistent with super-solar metallicities, with the
best fit given by the 2.5 Z_sun models. We derive a dynamical mass of 4E11
M_sun within the effective radius from the velocity dispersion. The EELR
spectra clearly indicate that the EELR is photoionized by the hidden central
engine. Photoionization modeling shows evidence that the gas metallicity in
both the EELR and the nuclear narrow-line region is mildly sub-solar (0.3 - 0.7
Z_sun) -- significantly lower than the super-solar metallicities deduced from
typical active galactic nuclei in the SDSS. The more luminous filaments in the
EELR exhibit a velocity field consistent with a common disk rotation. Fainter
clouds, however, show high approaching velocities that are uncoupled with this
apparent disk rotation. The striking similarities between this EELR and the
EELRs around steep-spectrum radio-loud quasars provide further evidence for the
orientation-dependent unification schemes. The metal-poor gas is almost
certainly not native to the massive host galaxy. We suggest that the close
companion galaxy could be the tidally stripped bulge of a late-type galaxy that
is merging with the host galaxy. The interstellar medium of such a galaxy is
probably the source for the low-metallicity gas in 3C79.Comment: Accepted for publication in ApJ. 13 pages, 12 figures, 3 tables.
Paper with figures at full resolution uploaded in this versio
The first VLBI image of an Infrared-Faint Radio Source
Context: To investigate the joint evolution of active galactic nuclei and
star formation in the Universe. Aims: In the 1.4 GHz survey with the Australia
Telescope Compact Array of the Chandra Deep Field South and the European Large
Area ISO Survey - S1 we have identified a class of objects which are strong in
the radio but have no detectable infrared and optical counterparts. This class
has been called Infrared-Faint Radio Sources, or IFRS. 53 sources out of 2002
have been classified as IFRS. It is not known what these objects are. Methods:
To address the many possible explanations as to what the nature of these
objects is we have observed four sources with the Australian Long Baseline
Array. Results: We have detected and imaged one of the four sources observed.
Assuming that the source is at a high redshift, we find its properties in
agreement with properties of Compact Steep Spectrum sources. However, due to
the lack of optical and infrared data the constraints are not particularly
strong.Comment: Accepted for publication in Astronomy and Astrophysics, 5 pages,
needs aa.cl
Implications for unified schemes from submillimetre and far-infrared follow-up of radio-selected samples
We extend our previous analysis which used generalized luminosity functions
(GLFs) to predict the number of quasars and galaxies in
low-radio-frequency-selected samples as a function of redshift, radio
luminosity, narrow-emission-line luminosity and type of unified scheme. Our
extended analysis incorporates the observed submillimetre (850 micron) flux
densities of radio sources, employs a new method which allows us to deal with
non detections, and focuses on the high-luminosity population. First, we
conclude that the submillimetre luminosity L_{850} of low-frequency-selected
radio sources is correlated with the bolometric luminosity L_{Bol} of their
quasar nuclei via an approximate scaling relation L_{850} \propto L_{Bol}^{0.7
\pm 0.2}. Second, we conclude that there is quantitative evidence for a
receding-torus-like physical process for the high-luminosity population within
a two-population unified scheme for radio sources; this evidence comes from the
fact that radio quasars are brighter in both narrow emission lines and
submillimetre luminosity than radio galaxies matched in radio luminosity and
redshift. Third, we note that the combination of a receding-torus-like scheme
and the assumption that the observed submillimetre emission is dominated by
quasar-heated dust yields a scaling relation L_{850} \propto L_{Bol}^{0.5}
which is within the errors of that determined here for radio-selected quasars,
and consistent with that inferred for radio-quiet quasars by Willott, Rawlings
& Grimes (2003).Comment: 13 pages (including an appendix), 5 figures, to appear in MNRA
The origin of the infrared emission in radio galaxies II: analysis of mid- to far-infrared Spitzer observations of the 2Jy sample
We present an analysis of deep mid- to far-infrared (MFIR) Spitzer
photometric observations of the southern 2Jy sample of powerful radio sources
(0.05 < z < 0.7), conducting a statistical investigation of the links between
radio jet, AGN, starburst activity and MFIR properties. This is part of an
ongoing extensive study of powerful radio galaxies that benefits from both
complete optical emission line information and a uniquely high detection rate
in the far-infrared (far-IR). We find tight correlations between the MFIR and
[OIII] emission luminosities, which are significantly better than those between
MFIR and extended radio luminosities, or between radio and [OIII] luminosities.
Since [OIII] is a known indicator of intrinsic AGN power, these correlations
confirm AGN illumination of the circum-nuclear dust as the primary heating
mechanism for the dust producing thermal MFIR emission at both 24 and 70
microns. We demonstrate that AGN heating is energetically feasible, and
identify the narrow line region clouds as the most likely location of the cool,
far-IR emitting dust. Starbursts make a major contribution to the heating of
the cool dust in only 15-28% of our targets.
We also investigate the orientation dependence of the continuum properties,
finding that the broad- and narrow-line objects in our sample with strong
emission lines have similar distributions of MFIR luminosities and colours.
Therefore our results are entirely consistent with the orientation-based
unified schemes for powerful radio galaxies. However, the weak line radio
galaxies (WLRG) form a separate class of objects with intrinsically low
luminosity AGN in which both the optical emission lines and the MFIR continuum
are weak.Comment: 29 pages, 5 figures, Accepted for publication in The Astrophysical
Journa
Spitzer Observations of 3C Quasars and Radio Galaxies: Mid-Infrared Properties of Powerful Radio Sources
We have measured mid-infrared radiation from an orientation-unbiased sample
of 3CRR galaxies and quasars at redshifts 0.4 < z < 1.2 with the IRS and MIPS
instruments on the Spitzer Space Telescope. Powerful emission (L_24micron >
10^22.4 W/Hz/sr) was detected from all but one of the sources. We fit the
Spitzer data as well as other measurements from the literature with synchrotron
and dust components. The IRS data provide powerful constraints on the fits. At
15 microns, quasars are typically four times brighter than radio galaxies with
the same isotropic radio power. Based on our fits, half of this difference can
be attributed to the presence of non-thermal emission in the quasars but not
the radio galaxies. The other half is consistent with dust absorption in the
radio galaxies but not the quasars. Fitted optical depths are anti-correlated
with core dominance, from which we infer an equatorial distribution of dust
around the central engine. The median optical depth at 9.7 microns for objects
with core-dominance factor R > 10^-2 is approximately 0.4; for objects with R <
10^-2, it is 1.1. We have thus addressed a long-standing question in the
unification of FR II quasars and galaxies: quasars are more luminous in the
mid-infrared than galaxies because of a combination of Doppler-boosted
synchrotron emission in quasars and extinction in galaxies, both
orientation-dependent effects.Comment: 42 pages, 14 figures plus two landscape tables. Accepted for
publication in Ap
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