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|A catalogue of ultra-luminous X-ray source coincidences with FIRST radio sources|
Aims.We search for ultra luminous X-ray source (ULXs) radio counterpartslocated in nearby galaxies in order to constrain their physicalnature. Methods: .Our work is based on a systematiccross-identification of the most recent and extensive available ULXcatalogues and archival radio data. Results: .A catalogue of 70positional coincidences is reported. Most of them are located within thegalaxy nucleus. Among them, we find 11 new cases of non-nuclear ULXsources with possibly associated radio emission.
|The H I Kinematics and Distribution of Four Blue Compact Dwarf Galaxies|
We present VLA H I observations of the blue compact dwarf (BCD) galaxiesNGC 2366, NGC 4861, VII Zw 403, and Haro 2. These galaxies span a rangeof BCD morphological types. The cometary-like BCDs NGC 2366 and NGC 4861have regular rotational kinematics with a V/σ of 8.7 and 6.4,respectively. On the other hand, the velocity fields of the iE BCD VIIZw 403 and of the nE BCD Haro 2 lack regularity, and their rotationalmotion is around the major, not the minor, axis. The H I distribution iscentrally peaked in VII Zw 403 and Haro 2, a general feature of all iEand nE-type BCDs, the most common ones. In contrast, cometary-type BCDshave multiple H I peaks that are scattered over the disk. The activeregions of star formation are associated with regions of high H I columndensities, with slight displacements between the H I and stellar peaks.NGC 2366 shows many H I minima, resulting from the disruptive influenceof massive star formation and supernovae on the interstellar medium(ISM). In NGC 2366 and NGC 4861, there is a tendency for H I gas with ahigher velocity dispersion to be associated with regions of lower H Icolumn density. This anticorrelation can be understood in the context ofa two-phase model of the ISM. In all BCDs, the radio continuum emissionis associated with the star-forming regions and is predominantly thermalin nature. H I clouds with no optical counterparts have been found inthe vicinity of NGC 4861 and Haro 2.Based on observations obtained at the National Radio AstronomyObservatory, a facility of the National Science Foundation, operatedunder cooperative agreement by Associated Universities, Inc.
|A Search for H I in Five Elliptical Galaxies with Fine Structure|
We report on VLA H I spectral line observations of five early-typegalaxies classified as optically peculiar because of the presence ofjets, ripples, or other optical fine structure. We detect H I within theprimary beam (30' half-power beamwidth) in four of the five systems.However, in only one case is this gas associated with the targetedelliptical galaxy. In the other cases the H I is associated with anearby gas-rich disk or dwarf galaxy. The one H I detection is for NGC7626, where we tentatively detect an H I cloud lying between 20 and 40kpc southwest of the galaxy center. Its origin is unclear. Our failureto detect obvious tidal H I features suggests that if thesefine-structure elliptical galaxies are remnants of disk galaxy mergers,either the progenitors were gas-poor or they are well evolved and anygaseous tidal features have dispersed and/or been converted into otherphases. Our targeted systems all reside in groups or clusters, and itseems likely that tidal H I is shorter lived in these environments thansuggested by studies of more isolated merger remnants.
|The Westerbork HI survey of spiral and irregular galaxies. II. R-band surface photometry of late-type dwarf galaxies|
R-band surface photometry is presented for 171 late-type dwarf andirregular galaxies. For a subsample of 46 galaxies B-band photometry ispresented as well. We present surface brightness profiles as well asisophotal and photometric parameters including magnitudes, diameters andcentral surface brightnesses. Absolute photometry is accurate to 0.1 magor better for 77% of the sample. For over 85% of the galaxies the radialsurface brightness profiles are consistent with published data withinthe measured photometric uncertainty. For most of the galaxies in thesample H I data have been obtained with the Westerbork Synthesis RadioTelescope. The galaxies in our sample are part of the WHISP project(Westerbork H I Survey of Spiral and Irregular Galaxies), which aims atmapping about 500 nearby spiral and irregular galaxies in H I. Theavailability of H I data makes this data set useful for a wide range ofstudies of the structure, dark matter content and kinematics oflate-type dwarf galaxies. Based on observations made with INT operatedon the island of La Palma by the Isaac Newton Group in the SpanishObservatorio del Roque de los Muchachos of the Instituto de Astrofisicade Canarias. The tables in Appendix A are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/390/863. Thefigures in Appendix B are only available in electronic formhttp://www.edpsciences.org
|Panchromatic Study of Nearby Ultraviolet-bright Starburst Galaxies: Implications for Massive Star Formation and High-Redshift Galaxies|
We present a panchromatic study of nearby starburst galaxies from theultraviolet to the visible, including narrowband Hα usingWisconsin-Indiana-Yale-NOAO (WIYN) and Hubble Space Telescope data, todetermine how star formation processes affect the morphologies andintegrated fluxes of nearby starbursts. We find that the UV and Hαmorphologies of starbursts tend to differ, although not in a standard orpredictable manner. From our sample of six nearby starbursts, threesystems show good correlations between UV and Hα fluxes, but wefind differences in UV and Hα morphology among the other three.Occasionally we find systems with well-defined H II regions without thecorresponding brightness in the UV, and vice versa. We discuss thelikely mechanisms behind these differences, which include starburstages, dust absorption, stellar energy ejecta through supernovae andwinds, and leakage of UV photons from stellar clusters. We conclude thatthe large-scale morphological features in starbursts are primarily dueto both age and absorption from a ``picket-fence'' dust distribution. Wefurther demonstrate the similarity and differences between these nearbystarbursts and high-redshift star-forming galaxies. The overallmorphology of our sample of starbursts changes little between UV andvisible wavelengths. If high-redshift galaxies are similar to thesestarbursts, their morphologies should change little between rest-frameUV and optical. We also show that FIR and UV spectral energydistributions and slopes can be used to determine large-scalemorphological features for extreme starbursts, with the steepest FIRslopes correlating with the most disturbed galaxies.
|The CfA Redshift Survey: Data for the NGP +36 Zone|
We have assembled redshifts for a complete sample of 719 galaxies withm_zw_ <= 15.5 in the declination range 32.5^deg^ <= δ <=38.5^deg^ and right ascension range 8^h^ <= α <= 17^h^. Wehave determined morphological types for all galaxies in the magnitudelimited sample by direct inspection of the POSS-O plates. 576 of theredshifts are measurements from Mount Hopkins, and 405 are newredshifts. We also include new redshifts for 77 fainter galaxies in thesame strip.
|CCD imaging of NGC 4861: Ionized gas properties and stellar formation|
This work undertakes the study of the galaxy NGC 4861, using imagingcentered at the strong lines H-alpha, H-beta, (O III) lambda 5007 andnearby continua. Integrated, absolute fluxes of 28 H II regions, and theregion known as the bright knot, have been measured showing correlationsbetween the equivalent width of H-beta and the excitation index log ((OIII)/H-beta). An excitation gradient has been detected along the chainof H II regions extending northwards from the bright knot, which isunusual for irregular galaxies like NGC 4861. We suggest that thisgradient is due to different stages of evolution, or ages, of the H IIregions. The continuum fluxes of eight emissionless associations and thecontinuum colors of the companion galaxy IC 3961 have also beenmeasured, and the presence of ionized gas cannot be detected. The ageand mass of the stellar population and ionizing stars of the bright knotwere subsequently estimated. It was also verified that this region isthe most important burst of star formation in NGC 4861.
|CCD Imaging of NGC4861 - Morphology and Brightness Distribution|
We discuss narrow band CCD imaging of NGC 4861 in continua at 4500 A,5300 A and 6300 A as well as in Hα, Hβ and (O III]λ5007 A lines. We find that the system exhibits a double nucleusstructure and a counter-tail to the well-known northeast chain of HIIregions. The mean value of lines and continua frames for the main bodybrightness distribution of NGC 4861 is R^-2.04+/-0.35^, comparable tothe Hubble-Reynolds law R^-2^. The three mentioned characteristicsindicate that NGC 4861 might have undergone a merger process. The timeelapsed from the beginning of the phenomenon is set to be smaller thanthree crossing times. New observations are proposed to confirm or rejectthe merger scenario for this peculiar galaxy.
|An atlas of ultraviolet spectra of star-forming galaxies|
A systematic study is presented of the UV spectra of star-forminggalaxies of different morphological type and activity class using asample drawn from a uniformly reduced IUE data set. The spectra for awide variety of galaxies, including normal spiral, LINER, starburst,blue compact, blue compact dwarf, and Seyfert 2 galaxies, are presentedin the form of spectral energy distributions to demonstrate the overallcharacteristics according to morphology and activity class and in theform of absolute flux distributions to better show the absorption andemission features of individual objects. The data support the picturebased on UV spectra of the Orbiting Astronomical Observatory and of theAstronautical Netherlands Satellite that spiral galaxies of later Hubbleclass have more flux at the shortest UV wavelengths than do spiralgalaxies of earlier Hubble class.
|Narrow band CCD imagery of NGC 4861 on H-alpha, H-beta, [OIII]_lambda5007 and nearby continua.|
|Mean galaxy luminosity classifications|
To prepare a catalog of weighted means on the classification system ofvan den Bergh, we have combined eight independent lists of luminosityclass estimates, L. Luminosity class values from each set weretransformed to the standard system and weighted according to the errorsderived through a statistical comparison of L differences betweencatalog pairs. Relations were derived for predicting accidental errorsassociated with galaxy diameter and inclination. In addition, we presentformulas for correcting systematic errors associated with diameter andinclination. Finally, we tabulate a high weight subsample of the meanluminosity classes usable as standards. Most values are tabulated in theThird Reference Catalog of Bright Galaxies.
|Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members|
This paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent.
|Radial velocities of double galaxies|
Spectral observations of 92 galaxies in isolated pairs have been carriedout. In 52 cases radial velocities were measured. The mean value of theorbital mass-to-luminosity ratio for 18 pairs is (16.2 plus or minus10.0) times the solar value.
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