141 research outputs found
Observations of the bright radio sources in the North Celestial Pole region at the RATAN-600 radio telescope
A survey of the North Celestial Pole region using the RATAN-600 radio
telescope at five frequencies in the range 2.3 to 21.7 GHz is described.
Sources were chosen from the NVSS catalogue. The flux densities of 171 sources
in the Declination range +75 to +88 are presented; typical flux density errors
are 5-10 percent including calibration errors. About 20 percent of the sources
have flat spectra or a flat component.Comment: 21 pages, 7 figures; to be published in Astronomy and Astrophysics
(without last figure with the spectra of the observed sources
The Evolution of Radio Galaxies at Intermediate Redshift
We describe a new estimate of the radio galaxy 1.4 GHz luminosity function
and its evolution at intermediate redshifts (z~0.4). Photometric redshifts and
color selection have been used to select Bj<23.5 early-type galaxies from the
Panoramic Deep Fields, a multicolor survey of two 25 sq deg fields.
Approximately 230 radio galaxies have then been selected by matching early-type
galaxies with NVSS radio sources brighter than 5 mJy. Estimates of the 1.4 GHz
luminosity function of radio galaxies measure significant evolution over the
observed redshift range. For an Omega_M=1 cosmology the evolution of the radio
power is consistent with luminosity evolution where P(z)=P(0)(1+z)^{k_L} and
3<k_L<5. The observed evolution is similar to that observed for UVX and X-ray
selected AGN and is consistent with the same physical process being responsible
for the optical and radio luminosity evolution of AGN.Comment: 26 pages, 9 Figures, Accepted for Publication in A
Polarization of the WMAP Point Sources
The detection of polarized sources in the WMAP 5-year data is a very
difficult task. The maps are dominated by instrumental noise and only a handful
of sources show up as clear peaks in the Q and U maps. Optimal linear filters
applied at the position of known bright sources detect with a high level of
significance a polarized flux P from many more sources, but estimates of P are
liable to biases. Using a new technique, named the "filtered fusion technique",
we have detected in polarization, with a significance level greater than 99.99%
in at least one WMAP channel, 22 objects, 5 of which, however, do not have a
plausible low radio frequency counterpart and are therefore doubtful. Estimated
polarized fluxes P < 400 mJy at 23 GHz were found to be severely affected by
the Eddington bias. The corresponding polarized flux limit for Planck/LFI at 30
GHz, obtained via realistic simulations, is 300 mJy. We have also obtained
statistical estimates of, or upper limits to the mean polarization degrees of
bright WMAP sources at 23, 33, 41, and 61 GHz, finding that they are of a few
percent.Comment: 10 pages, 6 figures. Accepted for publication in Ap
A synchrotron self-Compton model with low energy electron cut-off for the blazar S5 0716+714
Rapid inverse Compton cooling sets in when the brightness temperature (T_B)
of a self-absorbed synchrotron source with power-law electrons reaches ~10^{12}
K. However, T_B inferred from observations of intra-day variable sources (IDV)
are well above the "Compton catastrophe" limit. This can be understood if the
underlying electron distribution cuts off at low energy. We approximate a
low-energy cut-off with monoenergetic electrons. We compute the synchrotron
self-Compton (SSC) spectrum of such distribution, and using the IDV source
S5~0716+714 as an example, we compare it to the observed SED of S5~0716+714.
The hard radio spectrum is well-fitted by this model, and the optical data can
be accommodated by a power-law extension to the electron spectrum. We therefore
examine the scenario of an injection of electrons that is a double power law in
energy with a hard low-energy component that does not contribute to the
synchrotron opacity. We show that the double power-law injection model is in
good agreement with the observed SED of S5~0716+714. For intrinsic variability,
we find that a Doppler factor of D\geq30 can explain the observed SED provided
that low-frequency (<32 GHz) emission originates from a larger region than the
higher-frequency emission. To fit the entire spectrum, D\geq65 is needed. We
find the constraint imposed by induced Compton scattering at high T_B is
insignificant in our model. We confirm that electron distribution with a
low-energy cut-off can explain the high T_B in compact radio sources. We show
that synchrotron spectrum from such distributions naturally accounts for the
observed hard radio continuum with a softer optical component, without the need
for an inhomogeneous source.Comment: 13 pages, 5 figures, 1 table, to appear in A&A; refereces removed
from caption of Fig.3, added acknowledgemen
WMAP anomalous signal in the ecliptic plane
We report the detection of a high Galactic latitude, large scale, 7-sigma
signal in WMAP 5yr and spatially correlated with the ecliptic plane. Two
possible candidates are studied, namely unresolved sources and Zodiacal light
emission. We determine the strength of the Zodiacal light emission at WMAP
frequencies and estimate the contribution from unresolved extragalactic
sources. Neither the standard Zodiacal light emission nor the unresolved
sources alone seem to be able to explain the observed signal. Other possible
interpretations like Galactic foregrounds and diffuse Sunyaev-Zel'dovich effect
also seem unlikely. We check if our findings could affect the low-l anomalies
which have been reported in the WMAP data. Neither Zodiacal light emission nor
unresolved point source residuals seem to affect significantly the quadrupole
and octupole measurements. However, a signal with a quasi-blackbody spectrum
and with a spatial distribution similar to the Zodiacal light emission, could
explain both the anomalous signal and the low-ell anomalies. Future data
(Planck) will be needed in order to explain the origin of this signal.Comment: 8 pages, 9 figures. Submitted to MNRA
Contribution to the Diffuse Radio Background from Extragalactic Radio Sources
We examine the brightness of the Cosmic Radio Background (CRB) by comparing
the contribution from individual source counts to absolute measurements. We use
a compilation of radio counts to estimate the contribution of detected sources
to the CRB in several different frequency bands.We apply a Monte Carlo Markov
Chain technique to estimate the brightness values and uncertainties, paying
attention to various sources of systematic error. We compare our results to
absolute measurements from the ARCADE 2 experiment. At v = 150 MHz, 325 MHz,
408 MHz, 610 MHz, 1.4 GHz, 4.8 GHz, and 8.4 GHz our calculated contributions to
the background sky temperature are 18, 2.8, 1.6, 0.71, 0.11, 0.0032, 0.0059 K,
respectively. If the ARCADE 2 measurements are correct and come from sources,
then there must be an additional population of radio galaxies, fainter than
where current data are probing. More specifically, the Euclidean-normalized
counts at 1.4 GHz have to have an additional bump below about 10 {\mu}Jy.Comment: 9 pages, 7 figures, 3 tables, accepted MNRA
Fertility and gonadal function in female survivors after treatment of early unfavorable Hodgkin lymphoma (HL) within the German Hodgkin Study Group HD14 trial
Background In the HD14 trial, 2× BEACOPPescalated+2× ABVD (2+2) has improved the primary outcome. Compared with 4× ABVD, this benefit might be compromised by more infertility in women. Therefore, we analyzed gonadal function and fertility. Patients and methods Women ≤45 years in ongoing remission at least 1 year after therapy were included. Hormone parameters, menopausal symptoms, measures to preserve fertility, menstrual cycle, pregnancies, and offspring were evaluated. Results Three hundred and thirty one of 579 women addressed participated (57.2%) and 263 per-protocol treated patients qualified (A=ABVD: 137, B=2+2: 126, mean time after therapy 42 and 43 months, respectively). Regular menstrual cycle after treatment (A: 87%, B: 83%) and time to recovery (≤12 months) were not different. Follicle-stimulating hormone and anti-Muellerian hormone were significantly better in arm A. However, pregnancies after therapy favored arm B (A: 15%, B: 26%, P=0.043) and motherhood rates were equivalent to the German normal population. Multivariate analysis revealed prophylactic use of gonadotropin-releasing hormone (GnRH) analogues as highly significant prognostic factor for preservation of fertility (odds ratio=12.87, P=0.001). Severe menopausal symptoms were frequent in women ≥30 years (A: 21%, B: 25%). Conclusions Hormonal levels after 2+2 indicate a reduced ovarian reserve. However, 2+2 in combination with GnRH analogues does not compromise fertility within the evaluated observation tim
Radio to infrared spectra of late-type galaxies with Planck and WMAP data
We use the Planck Early Release Compact Source Catalogue combined with WMAP
and other archival measurements to construct continuum spectra of three nearby
dusty star-forming galaxies: Messier 82, NGC 253 and NGC 4945. We carry out a
least-squares fit to the spectra using a combination of simple synchrotron,
free-free and thermal dust models, and look for evidence of anomalous microwave
emission (AME). We find that the radio spectra of all three galaxies are
consistent with steep spectrum synchrotron emission, with a significant amount
of free-free emission required to explain the Planck and WMAP data points in
the frequency range 30-150 GHz. This brings the star-formation rate based on
free-free emission into better agreement with that from the non-thermal
emission. We place limits on the presence of AME in these galaxies, finding
that it is lower than expectations based on the ratio of far infrared to AME
from the Galaxy. Nevertheless, the shape of the spectrum of NGC 4945 hints at
the presence of AME with a peak around 30 GHz. Future Planck data will let us
look more closely at these galaxies, as well as to extend the analysis to many
more galaxies.Comment: 5 pages, 1 figure (6 panels), 1 table. Submitted to MNRAS letter
3C 57 as an Atypical Radio-Loud Quasar: Implications for the Radio-Loud/Radio-Quiet Dichotomy
Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the
4D Eigenvector 1 (4DE1) parameter space which implies restricted
geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ)
majority of quasars. We discuss how this restricted domain for the LD RL parent
population supports the notion for a RQ-RL dichotomy among Type 1 sources. 3C
57 is an atypical RL quasar that shows both uncertain radio morphology and
falls in a region of 4DE1 space where RL quasars are rare.
We present new radio flux and optical spectroscopic measures designed to
verify its atypical optical/UV spectroscopic behaviour and clarify its radio
structure. The former data confirms that 3C 57 falls off the 4DE1 quasar "main
sequence" with both extreme optical FeII emission (R_{FeII} ~ 1) and a large
CIV 1549 profile blueshift (~ -1500 km/s). These parameter values are typical
of extreme Population A sources which are almost always RQ. New radio measures
show no evidence for flux change over a 50+ year timescale consistent with
compact steep-spectrum (CSS or young LD) over core-dominated morphology. In the
4DE1 context where LD RL are usually low L/L_{Edd} quasars we suggest that 3C
57 is an evolved RL quasar (i.e. large Black Hole mass) undergoing a major
accretion event leading to a rejuvenation reflected by strong FeII emission,
perhaps indicating significant heavy metal enrichment, high bolometric
luminosity for a low redshift source and resultant unusually high Eddington
ratio giving rise to the atypical CIV 1549.Comment: Accepted for publication in MNRAS; 10 pages, 6 figures, 4 table
Galaxy Populations and Evolution in Clusters IV: Deep HI Observations of Dwarf Ellipticals in the Virgo Cluster
We present in this paper the deepest Arecibo HI observations of Virgo cluster
dwarf ellipticals (dEs) taken to date. Based on this data we argue that a
significant fraction of Virgo cluster dEs recently underwent evolution. Our new
observations consist of HI 21-cm line observations for 22 classified dE
galaxies with optical radial velocities consistent with membership in the Virgo
cluster. Cluster members VCC 390 and VCC 1713 are detected with HI masses M(HI)
= 6*10^7 M_solar and 8*10^7 M_solar, respectively, while M(HI) in the remaining
20 dE galaxies have upper limits as low as 5*10^5 M_solar. We combine our
results with those for 27 other Virgo cluster dEs with HI observations in the
literature, 7 of which have HI detection claims. New optical images from the
WIYN telescope of 5 of these HI-detected dEs, along with archival data, suggest
that seven of the claimed detections are real, yielding a ~ 15% detection rate.
These HI-detected classified dEs are preferentially located near the periphery
of the Virgo cluster. Three Virgo dEs have observed HI velocity widths > 200
km/s, possibly indicating the presence of a large dark matter content, or
transient extended HI. We discuss the possible origins of these objects and
argue that they originate from field galaxies accreted onto high angular
momentum orbits by Virgo in the last few Gyr. As a result these galaxies are
slowly transformed within the cluster by gradual gas stripping processes,
associated truncation of star formation, and passive fading of stellar
populations. Low-mass early-type cluster galaxies are therefore currently being
produced as the product of cluster environmental effects. We utilize our
results to estimate the recent (past 1-3 Gyr) average mass accretion rate into
the Virgo cluster, finding dM/dt ~ 50 M_solar/year.Comment: Accepted to ApJ, 21 page
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