1,454 research outputs found

    Compact X-ray and extreme-ultraviolet light sources

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    Evidence for Intrinsic Redshifts in Normal Spiral Galaxies

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    The Tully-Fisher Relationship (TFR) is utilized to identify anomalous redshifts in normal spiral galaxies. Three redshift anomalies are identified in this analysis: (1) Several clusters of galaxies are examined in which late type spirals have significant excess redshifts relative to early type spirals in the same clusters, (2) Galaxies of morphology similar to ScI galaxies are found to have a systematic excess redshift relative to the redshifts expected if the Hubble Constant is 72 km s-1 Mpc-1, (3) individual galaxies, pairs, and groups are identified which strongly deviate from the predictions of a smooth Hubble flow. These redshift deviations are significantly larger than can be explained by peculiar motions and TFR errors. It is concluded that the redshift anomalies identified in this analysis are consistent with previous claims for large non-cosmological (intrinsic) redshifts.Comment: Accepted for publication at Astrophysics&Space Science. 36 pages including 8 tables and 7 figure

    Coordinates and 2MASS and OGLE identifications for all stars in Arp's 1965 finding chart for Baade's Window

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    Aims: We seek to provide 2MASS and OGLE identifications and coordinates for all stars in the finding chart published by Arp\,(1965). This chart covers the low extinction area around NGC 6522, also known as Baade's window, at coordinates (l,b)=(1.02,-3.92). Methods: A cross correlation, using numerical techniques, was performed between a scan of the original finding chart from Arp (1965) and 2MASS and OGLE-II images and stellar coordinates. Results: We provide coordinates for all stars in Arp's finding chart and 2MASS and OGLE identifications wherever possible. Two identifications in quadrant II do not appear in the original finding chart.Comment: 30 pages, accepted by A&A as a Research Not

    Massive Coronae of Galaxies

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    There is reason to suspect that about half of the baryons are in pressure-supported plasma in the halos of normal galaxies, drawn in by gravity along with about half of the dark matter. To be consistent with the observations this baryonic component, the corona, would have to be hotter than the kinetic temperature of the dark matter in the halo so as to produce acceptable central electron densities. We ascribe this hotter plasma temperature to the addition of entropy prior to and during assembly of the system, in an analogy to cluster formation. The plasma cooling time would be longer than the gravitational collapse time but, in the inner parts, shorter than the Hubble time, making the corona thermally unstable to the formation of a cloudy structure that may be in line with what is indicated by quasar absorption line systems. The corona of an isolated spiral galaxy would be a source of soft X-ray and recombination radiation, adding to the more commonly discussed effects of stars and supernovae. In this picture the mass in the corona is much larger than the mass in condensed baryons in a spiral galaxy. The corona thus would be a substantial reservoir of diffuse baryons that are settling and adding to the mass in interstellar matter and stars, so that star formation in isolated spirals will continue well beyond the present epoch.Comment: 14 pages, 5 figure

    The Distribution of Redshifts in New Samples of Quasi-stellar Objects

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    Two new samples of QSOs have been constructed from recent surveys to test the hypothesis that the redshift distribution of bright QSOs is periodic in log(1+z)\log(1+z). The first of these comprises 57 different redshifts among all known close pairs or multiple QSOs, with image separations \leq 10\arcsec, and the second consists of 39 QSOs selected through their X-ray emission and their proximity to bright comparatively nearby active galaxies. The redshift distributions of the samples are found to exhibit distinct peaks with a periodic separation of 0.089\sim 0.089 in log(1+z)\log(1+z) identical to that claimed in earlier samples but now extended out to higher redshift peaks z=2.63,3.45z = 2.63, 3.45 and 4.47, predicted by the formula but never seen before. The periodicity is also seen in a third sample, the 78 QSOs of the 3C and 3CR catalogues. It is present in these three datasets at an overall significance level 10510^{-5} - 10610^{-6}, and appears not to be explicable by spectroscopic or similar selection effects. Possible interpretations are briefly discussed.Comment: submitted for publication in the Astronomical Journal, 15 figure

    Arp 302: Non-starburst Luminous Infrared Galaxies

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    Arp 302, a luminous infrared source (L_{IR} = 4.2x10^{11} Lsun), consisting of two spiral galaxies (VV340A and VV340B) with nuclear separation of 40'', has the highest CO luminosity known. Observations with the BIMA array at 5'' X 7'' resolution reveal that the CO emission is extended over 23.0 kpc in the edge-on spiral galaxy, VV340A, corresponding to 6.7x10^{10} Msun of H_2. In the companion face-on galaxy, VV340B, the CO emission is extended over ~10.0 kpc, with 1.1x10^{10} Msun of H_2. The large CO extent is in strong contrast to starburst systems, such as Arp 220, in which the CO extent is typically \le 1 kpc. Furthermore, LIR/ML_{IR}/M(H_2) is found to be \le 6.0 Lsun/Msun throughout both galaxies. Thus the high IR luminosity of Arp 302 is apparently not due to starbursts in the nuclear regions, but is due to its unusually large amount of molecular gas forming stars at a rate similar to giant molecular clouds in the Milky Way disk. Arp 302 consists of a pair of very gas-rich spiral galaxies that may be interacting and in a phase before a likely onset of starbursts.Comment: AAS Latex plus two postscript figures. ApJ Letters (accepted

    A Molecular Tidal Tail in the Medusa Minor Merger

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    We have detected CO 1-0 emission along the tidal tail of the NGC 4194 (the Medusa) merger. It is the first CO detection in the optical tail of a minor merger. Emission is detected both in the centre of the tail and at its tip. The molecular mass in the 33'' Onsala 20m beam is estimated to be >= 8.5 x 10^7 M_{sun} which is at least 4% of the total molecular mass measured so far in this system. We suggest that the emission is a molecular tidal tail which is part of the extended structure of the main body, and that the molecular gas was thrown out by the collision instead of having formed in situ from condensing atomic material. We find it unlikely that the emission is associated with a tidal dwarf galaxy (even if the future formation of such an object is possible), but high resolution HI, CO and optical observations are necessary to resolve the issue. The Medusa is very likely the result of an elliptical+spiral collison and our detection supports the notion that molecular gas in minor mergers can be found at great distances from the merger centre.Comment: 4 Pages, 2 figures included, accepted for A&A letter

    On time dilation in quasar light curves

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    In this paper we set out to measure time dilation in quasar light curves. In order to detect the effects of time dilation, sets of light curves from two monitoring programmes are used to construct Fourier power spectra covering timescales from 50 days to 28 years. Data from high and low redshift samples are compared to look for the changes expected from time dilation. The main result of the paper is that quasar light curves do not show the effects of time dilation. Several explanations are discussed, including the possibility that time dilation effects are exactly offset by an increase in timescale of variation associated with black hole growth, or that the variations are caused by microlensing in which case time dilation would not be expected.Comment: 8 pages, 5 figures. Accepted for publication in MNRAS. Published online 9 April 2010

    Globular Clusters as Candidates for Gravitational Lenses to Explain Quasar-Galaxy Associations

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    We argue that globular clusters (GCs) are good candidates for gravitational lenses in explaining quasar-galaxy associations. The catalog of associations (Bukhmastova 2001) compiled from the LEDA catalog of galaxies (Paturel 1997) and from the catalog of quasars (Veron-Cetty and Veron 1998) is used. Based on the new catalog containing 8382 pairs, we show that one might expect an increased number of GCs around irregular galaxies of types 9 and 10 from the hypothesis that distant compact sources are gravitationally lensed by GCs in the halos of foreground galaxies. The King model is used to determine the central surface densities of 135 GCs in the Milky Way. The distribution of GCs in central surface density was found to be lognormal.Comment: 22 pages, 4 figure
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