Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
The Nature of Nearby Counterparts to Intermediate-Redshift Luminous Compact Blue Galaxies. II. CO Observations
We present the results of a single-dish beam-matched survey of the threelowest rotational transitions of CO in a sample of 20 local (D<~70Mpc) luminous compact blue galaxies (LCBGs). These ~L*, blue, highsurface brightness, starbursting galaxies were selected on the samecriteria used to define LCBGs at higher redshifts. Our detection ratewas 70%, with those galaxies havingLB<7×109 Lsolar not detected.We find that the H2 masses of local LCBGs range from6.6×106 to 2.7×109 Msolar,assuming a Galactic CO-to-H2 conversion factor. Combiningthese results with our earlier H I survey of the same sample, we findthat the ratio of molecular to atomic gas mass is low, typically 5%-10%.Using a large velocity gradient model, we find that the average gasconditions of the entire interstellar medium in local LCBGs are similarto those found in the centers of star-forming regions in our Galaxy andin the nuclear regions of other galaxies. Star formation rates,determined from IRAS fluxes, are a few Msolaryr-1, much higher per unit dynamical mass than normal spiralgalaxies. If this rate remains constant, the molecular hydrogendepletion timescales are short, ~10-200 Myr.
| The Nature of Nearby Counterparts to Intermediate-Redshift Luminous Compact Blue Galaxies. I. Optical/H I Properties and Dynamical Masses
We present single-dish H I spectra obtained with the Green BankTelescope, along with optical photometric properties from the SloanDigital Sky Survey, of 20 nearby (D<~70 Mpc) luminous compact bluegalaxies (LCBGs). These ~L*, blue, high surface brightness, starburstinggalaxies were selected using the same criteria as were used to defineLCBGs at higher redshifts. We find that these galaxies are gas-rich,with MHI ranging from 5×108 to8×109 Msolar andMHIL-1B ranging from 0.2 to 2Msolar L-1solar, consistent with avariety of morphological types of galaxies. We find that the dynamicalmasses (measured within R25) span a wide range, from 1 to1×1011 Msolar. However, at least half havedynamical mass-to-light ratios smaller than those of nearby galaxies ofall Hubble types, as found for LCBGs at intermediate redshifts. Bycomparing line widths and effective radii with local galaxy populations,we find that LCBGs are consistent with the dynamical mass properties ofMagellanic (low luminosity) spiral galaxies and the more massiveirregular and dwarf elliptical galaxies, such as NGC 205.
| On the local radio luminosity function of galaxies. I. The Virgo cluster
We cross-correlate the galaxies brighter than m_B=18 in the Virgocluster with the radio sources in the NVSS survey (1.4 GHz), resultingin 180 radio-optical identifications. We determine the radio luminosityfunction of the Virgo galaxies, separately for the early- andlate-types. Late-type galaxies develop radio sources with a probabilityproportional to their optical luminosity. In fact their radio/optical(R_B) distribution is gaussian, centered at log R_B ~ -0.5, i.e. theradio luminosity is ~ 0.3 of the optical one. The probability oflate-type galaxies to develop radio sources is almost independent oftheir detailed Hubble type, except for Sa (and S0+S0a) which are afactor of ~ 5 less frequent than later types at any R_B. Giantelliptical galaxies feed ``monster" radio sources with a probabilitystrongly increasing with mass. However the frequency of fainter radiosources is progressively less sensitive on the system mass. The faintestgiant E galaxies (M_B=-17) have a probability of feeding low power radiosources similar to that of dwarf E galaxies as faint as M_B=-13. Table~1is only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A Complete Redshift Survey to the Zwicky Catalog Limit in a 2^h X 15 deg Region around 3C 273
We compile 1113 redshifts (648 new measurements, 465 from theliterature) for Zwicky catalog galaxies in the region (-3.5d <= delta<= 8.5d, 11h5 <= alpha <= 13h5). We include redshifts for 114component objects in 78 Zwicky catalog multiplets. The redshift surveyin this region is 99.5% complete to the Zwicky catalog limit, m_Zw =15.7. It is 99.9% complete to m_Zw = 15.5, the CfA Redshift Survey(CfA2) magnitude limit. The survey region is adjacent to the northernportion of CfA2, overlaps the northernmost slice of the Las CampanasRedshift Survey, includes the southern extent of the Virgo Cluster, andis roughly centered on the QSO 3C 273. As in other portions of theZwicky catalog, bright and faint galaxies trace the same large-scalestructure.
| The large-scale distribution of late-type galaxies between Virgo and the Great Wall
Neutral hydrogen data are presented for 88 of the Virgo Cluster Cataloggalaxies thought on morphological grounds to lie in the background ofthe cluster. We confirm that the morphological assignment of clustermembership works quite well; very few of the 'background' galaxies arein fact at cluster redshifts. The resulting sample of redshifts, alongwith optical redshifts from the literature, allow us to explore thelarge-scale distribution of galaxies in the space between the LocalSupercluster and the Great Wall. Galaxies in a larger window around theVirgo Cluster, but at redshifts between Virgo and the Great Wall, have afairly low average number density, but the distribution is far fromuniform: Some portions resemble voids, but in other portions galaxiescan be assigned to clouds or filaments of appreciable size (sometimescontaining bound groups). We investigate the luminosity function inhigh- and low-density regions of our galaxy sample, which excludes theVirgo Cluster proper. We find no significant difference. However, ourselection procedures are insensitive to galaxies of very low surfacebrightness, which have been reported to be more abundant in low-densityregions. The average probability of a line of sight intersecting theoptical disk of our sample galaxies is derived separately for the VirgoSupercluster region (redshifts below 3500 km/s) and for the regionbehind (out to 10,000 km/s). The number density ratio of Ly-alpha forestlines to galaxies is larger by a factor of order 10 in the far(low-density) region than in the near. A survey of recent literature ongalaxy redshifts uncovers a new candidate, MCG 0-32-16, for the lowestredshift absorption line.
| Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area.
The present catalog of 2096 galaxies within an area of about 140 sq degapproximately centered on the Virgo cluster should be an essentiallycomplete listing of all certain and possible cluster members,independent of morphological type. Cluster membership is essentiallydecided by galaxy morphology; for giants and the rare class of highsurface brightness dwarfs, membership rests on velocity data. While 1277of the catalog entries are considered members of the Virgo cluster, 574are possible members and 245 appear to be background Zwicky galaxies.Major-to-minor axis ratios are given for all galaxies brighter than B(T)= 18, as well as for many fainter ones.
| Accurate Optical Positions of Arakelian Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981AJ.....86..820K&db_key=AST
| Galaxies of high surface brightness
Two lists are presented which contain 621 galaxies whose surfacebrightness, as derived from their apparent magnitudes, is at least 22.0magnitudes from an area of 1 sq arcsec. The lists were compiled in anattempt to verify observationally a possible correlation between surfacebrightness and nuclear activity. Four percent of all the galaxies in anarea of 4.5 sr at declinations higher than -3 deg and galactic latitudesgreater than 20 deg are listed, including 30 Markarian, 29 Zwicky, and 7blue Haro galaxies. A morphological study of 130 of the galaxiesindicates that about half are elliptical or lenticular, 50 are compactor peculiar, and that there is an excess of elliptical and lenticularobjects in comparison with a random sample. Notes on the morphologicaltypes and colors of the galaxies are provided along with identificationcharts.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
Katalógusok és elnevezések:
|
