315 research outputs found
A spiral-like disk of ionized gas in IC 1459: Signature of a merging collision
The authors report the discovery of a large (15 kpc diameter) H alpha + (NII) emission-line disk in the elliptical galaxy IC 1459, showing weak spiral structure. The line flux peaks strongly at the nucleus and is more concentrated than the stellar continuum. The major axis of the disk of ionized gas coincides with that of the stellar body of the galaxy. The mass of the ionized gas is estimated to be approx. 1 times 10 (exp 5) solar mass, less than 1 percent of the total mass of gas present in IC 1459. The total gas mass of 4 times 10(exp 7) solar mass has been estimated from the dust mass derived from a broad-band color index image and the Infrared Astronomy Satellite (IRAS) data. The authors speculate that the presence of dust and gas in IC 1459 is a signature of a merger event
ISO far-infrared observations of rich galaxy clusters II. Sersic 159-03
The far-infrared emission from rich galaxy clusters is investigated. Maps
have been obtained by ISO at 60, 100, 135, and 200 microns using the PHT-C
camera. Ground based imaging and spectroscopy were also acquired. Here we
present the results for the cooling flow cluster Sersic 159-03. An infrared
source coincident with the dominant cD galaxy is found. Some off-center sources
are also present, but without any obvious counterparts.Comment: 6 pages, 4 postscript figures, accepted for publication in `Astronomy
and Astrophysics
New absolute magnitude calibrations for W Ursa Majoris type binaries
Parallaxes of W UMa stars in the Hipparcos catalogue have been analyzed. 31 W
UMa stars, which have the most accurate parallaxes ()
which are neither associated with a photometric tertiary nor with evidence of a
visual companion, were selected for re-calibrating the
Period--Luminosity--Color (PLC) relation of W UMa stars. Using the Lutz--Kelker
(LK) bias corrected (most probable) parallaxes, periods (),
and colors (0.04<<1.28) of the 31 selected W UMa, the PLC relation
have been revised and re-calibrated. The difference between the old (revised
but not bias corrected) and the new (LK bias corrected) relations are almost
negligible in predicting the distances of W UMa stars up to about 100 parsecs.
But, it increases and may become intolerable as distances of stars increase.
Additionally, using and colors from 2MASS (Two
Micron All Sky Survey) data, a PLC relation working with infrared data was
derived. It can be used with infrared colors in the range
, and . Despite {\em 2MASS}
data are single epoch observations, which are not guaranteed at maximum
brightness of the W UMa stars, the established relation has been found
surprisingly consistent and reliable in predicting LK corrected distances of W
UMa stars.Comment: 9 pages, 8 figures and 2 tables, accepted for publication in
Astronomische Nachrichte
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Recent results and perspectives on cosmic backgrounds from radio to far-infrared
© 2019 World Scientific Publishing Company. Cosmological and astrophysical surveys from radio to far-infrared, in both temperature and polarization, offer a unique view of the universe properties and of the formation and evolution of its structures. The last release, close to be finalized, of the Planck mission results sets the scene for cosmological models and parameters, while the comparison with other types of data sets raises the issue of possible tensions about some parameters, first of all the Hubble constant. At the same time, on the extragalactic side, Planck carried out the deepest systematic all-sky survey of SZ galaxy clusters and detected thousands of dusty galaxies and many hundreds of extragalactic radio sources, also allowing us to investigate many specific topics, including molecular hydrogen clouds in galactic halos. The exploitation of future generation of CMB missions and the next radio facilities will allow us to deeply investigate several topics in cosmology and astrophysics, from the existence of primordial gravitational waves to the energy releases in the primeval plasma, from the dawn ages and the epoch of reionization to the formation and evolution of early galaxies and clusters, while a wide set of open astrophysical problems can be studied with future IR missions
Recommended from our members
Recent results and perspectives on cosmic backgrounds from radio to far-infrared
© 2019 World Scientific Publishing Company. Cosmological and astrophysical surveys from radio to far-infrared, in both temperature and polarization, offer a unique view of the universe properties and of the formation and evolution of its structures. The last release, close to be finalized, of the Planck mission results sets the scene for cosmological models and parameters, while the comparison with other types of data sets raises the issue of possible tensions about some parameters, first of all the Hubble constant. At the same time, on the extragalactic side, Planck carried out the deepest systematic all-sky survey of SZ galaxy clusters and detected thousands of dusty galaxies and many hundreds of extragalactic radio sources, also allowing us to investigate many specific topics, including molecular hydrogen clouds in galactic halos. The exploitation of future generation of CMB missions and the next radio facilities will allow us to deeply investigate several topics in cosmology and astrophysics, from the existence of primordial gravitational waves to the energy releases in the primeval plasma, from the dawn ages and the epoch of reionization to the formation and evolution of early galaxies and clusters, while a wide set of open astrophysical problems can be studied with future IR missions
Recent results and perspectives on cosmology and fundamental physics from microwave surveys
Recent cosmic microwave background data in temperature and polarization have
reached high precision in estimating all the parameters that describe the
current so-called standard cosmological model. Recent results about the
integrated Sachs-Wolfe effect from cosmic microwave background anisotropies,
galaxy surveys, and their cross-correlations are presented. Looking at fine
signatures in the cosmic microwave background, such as the lack of power at low
multipoles, the primordial power spectrum and the bounds on non-Gaussianities,
complemented by galaxy surveys, we discuss inflationary physics and the
generation of primordial perturbations in the early Universe. Three important
topics in particle physics, the bounds on neutrinos masses and parameters, on
thermal axion mass and on the neutron lifetime derived from cosmological data
are reviewed, with attention to the comparison with laboratory experiment
results. Recent results from cosmic polarization rotation analyses aimed at
testing the Einstein equivalence principle are presented. Finally, we discuss
the perspectives of next radio facilities for the improvement of the analysis
of future cosmic microwave background spectral distortion experiments.Comment: 27 pages, 9 figures. Review Article. International Journal of Modern
Physics D, in press. [Will appear also on the proceedings of the Fourteenth
Marcel Grossmann Meeting University of Rome "La Sapienza" - Rome, July 12-18,
2015 (http://www.icra.it/mg/mg14/), eds. Robert T. Jantzen, Kjell Rosquist,
Remo Ruffini. World Scientific, Singapore
OVI Observations of Galaxy Clusters: Evidence for Modest Cooling Flows
A prediction of the galaxy cluster cooling flow model is that as gas cools
from the ambient cluster temperature, emission lines are produced in gas at
subsequently decreasing temperatures. Gas passing through 10^5.5 K emits in the
lines of OVI 1032,1035, and here we report a FUSE study of these lines in three
cooling flow clusters, Abell 426, Abell 1795, and AWM 7. No emission was
detected from AWM 7, but OVI is detected from the centers of Abell 426 and
Abell 1795, and possibly to the south of the center in Abell 1795, where X-ray
and optical emission line filaments lie. In Abell 426, these line luminosities
imply a cooling rate of 32+/-6 Msolar/yr within the central r = 6.2 kpc region,
while for Abell 1795, the central cooling rate is 26+/-7 Msolar/yr (within r =
22 kpc), and about 42+/-9 Msolar/yr including the southern pointing. Including
other studies, three of six clusters have OVI emission, and they also have star
formation as well as emission lines from 1E4 K gas. These observations are
generally consistent with the cooling flow model but at a rate closer to 30
Msolar/yr than originally suggested values of 100-1000 Msolar/yr.Comment: 17 pages, 6 figures, ApJ, in pres
On the Nature of the NGC 1275 System
Sub-arcsecond images, taken in B, R, and H-Alpha filters, and area
spectroscopy obtained with the WIYN 3.5-m telescope provide the basis for an
investigation of the unusual structures in the stellar body and ionized gas in
and around the Perseus cluster central galaxy, NGC 1275. Our H-Alpha filter is
tuned to gas at the velocity of NGC 1275, revealing complex, probably
unresolved, small-scale features in the extended ionized gas, located up to
50/h kpc from NGC 1275. The mean H-Alpha surface brightness varies little along
the outer filaments; this, together with the complex excitation state
demonstrated by spectra, imply that the filaments are likely to be tubes, or
ribbons, of gas. The morphology, location and inferred physical parameters of
the gas in the filaments are consistent with a model whereby the filaments form
through compression of the intracluster gas by relativistic plasma emitted from
the active nucleus of NGC 1275. Imaging spectroscopy with the Densepak fiber
array on WIYN suggests partial rotational support of the inner component of low
velocity ionized gas. We confirm and extend evidence for features in the
stellar body of NGC 1275, and identify outer stellar regions containing very
blue, probably very young, star clusters. We interpret these as evidence for
recent accretion of a gas-rich system, with subsequent star formation. We
suggest that two main processes, which may be causally connected, are
responsible for the rich phenomenology of the NGC 1275 system -- NGC 1275
experienced a recent merger/interaction with a group of gas-rich galaxies, and
recent outflows from its AGN have compressed the intracluster gas, and perhaps
the gas in the infalling galaxies, to produce a complex web of filaments.
(Abridged)Comment: AJ, accepted; a recommended full resolution version is available at
http://www.astro.wisc.edu/~chris/pera.p
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