Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
Interstellar Gas in the NGC 4410 Galaxy Group
We present new radio continuum, 21 cm H I, and 2.6 mm CO data for thepeculiar radio galaxy NGC 4410A and its companion NGC 4410B and comparewith available optical and X-ray maps. Our radio continuum maps show anasymmetric double-lobed structure, with a high surface brightness lobeextending 3.6′ (~100 kpc) to the southeast and a 6.2′(~180 kpc) low surface brightness feature in the northwest. Moleculargas is abundant in NGC 4410A, withMH2~4×109 Msolar(using the standard Galactic conversion factor) but is undetected in NGC4410B. H I is less abundant, with MHI~109Msolar for the pair. Our H I map shows a3×108 Msolar H I tail extending 1.7′(50 kpc) to the southeast of the pair, coincident with a faint opticaltail and partially overlapping with the southeastern radio lobe. The H Itail is anticoincident with a 2' (56 kpc) long X-ray structure alignedwith a stellar bridge that connects the pair to a third galaxy. If thisX-ray emission is associated with the group, we infer(3-8)×108 Msolar of hot gas in this feature.This may be either intracluster gas or shocked gas associated with thebridge. Our detection of abundant interstellar gas in this pair,including an H I-rich tidal tail near the southeastern radio lobe,suggests that the observed distortions in this lobe may have been causedby the interstellar medium in this system. The gravitational interactionof the two galaxies and the subsequent motion of the interstellar mediumin the system relative to the jet may have produced sufficient rampressure to bend and distort the radio jet. An alternative hypothesis isthat the jet was distorted by ram pressure due to an intraclustermedium, although the small radial velocity of NGC 4410A relative to thegroup and the lack of diffuse X-ray emission in the group makes thisless likely unless the group is not virialized or is in the process ofmerging with another group. Using our VLA data, we also searched for H Icounterparts to the other 10 known members of the NGC 4410 group and COfrom three other galaxies in the inner group. In our velocity range of6690-7850 km s-1, we detected six other galaxies above our HI sensitivity limits of 2×108 Msolar for theinner group and 4×108 Msolar for the outergroup. The total H I in the group is 1.4×1010Msolar, 80% of which arises from four galaxies in the outergroup. Three of these galaxies (VCC 822, VCC 831, and VCC 847) arespirals with MHI/LB ratios typical of fieldgalaxies, while FGC 170A appears to be a gas-rich dwarf galaxy(MB~-18, MHI~3×109Msolar). In the inner group, the SBa galaxy NGC 4410D (VCC934) was detected in H I and CO (MHI~5×108Msolar and MH2~8×108Msolar) and has a 1' (28 kpc) long H I tail that pointstoward the nearby disk galaxy NGC 4410F. NGC 4410F was also detected inH I (MHI~4×108 Msolar). Thegalaxies in the inner group appear to be somewhat deficient in H Icompared to their blue luminosities, suggesting phase changes driven bygalaxy-galaxy or galaxy-intracluster medium encounters.
| Far infrared and Ultraviolet emissions of individual galaxies at z=0: selection effects on the estimate of the dust extinction
We have cross-correlated Far Infrared (IRAS) and UV (FOCA) observationsof galaxies to construct a sample of FIR selected galaxies with a UVobservation at 0.2 mu m. The FIR and UV properties of this sample arecompared to the mean properties of the local Universe deduced from theluminosity distributions at both wavelengths. Almost all the galaxies ofour sample have a FIR to UV flux ratio larger than the ratio of the FIRand UV luminosity densities, this effect becoming worse as the galaxiesbecome brighter: the increase of the UV (0.2 mu m) extinction is about0.5 mag per decade of FIR (60 mu m) luminosity. Quantitative starformation rates are estimated by adding the contribution of the FIR andUV emissions. They are found consistent with the corrections forextinction deduced from the FIR to UV flux ratio. A total localvolume-average star formation rate is calculated by summing thecontribution of the FIR and UV wavelengths bands. Each band contributesfor an almost similar amount to the total star formation rate with rhoSFR = 0.03 +/- 0.01 h * Msun/yr/Mpc3 at z=0. Thisis equivalent to a global extinction of 0.75 mag to apply to the localluminosity density at 0.2 mu m. The trend of a larger FIR to UV fluxratio for a larger FIR luminosity found for our sample of nearbygalaxies is extended and amplified toward the very large FIRluminosities when we consider the galaxies detected by ISOCAM in a CFRSfield and the Ultra Luminous Infrared Galaxies at low and high redshift.A UV extinction is tentatively estimated for these objects.
| Optical identifications of the IRAS faint sources in the Virgo cluster area.
This paper presents a study on the deep optical identifications of 369IRAS faint sources in a 102 square degree area centered on the Virgocluster. We obtained the positions and magnitudes of candidates fromfour UK Schmidt Telescope IIIa-J direct plates. 89 (24%) are identifiedas stars and 276 (75%) as galaxies. There are 4 (1%) empty fields to theplate limit of B=~22. The infrared-optical database for 193 FSC-onlysources is given. Most of the IRAS galaxy sources are spirals. There are83 IRAS galaxy sources being regarded as the cluster members by Binggeliet al. (1985). In our sample, a correlation between the luminosity ratioL_IR_/L_B_ and the infrared flux ratio F(100μm)/F(60μm) isevident. For the member galaxies, a weak correlation between L_IR_/L_B_and L_IR_ is also found.
| Dwarf galaxies in the Virgo cluster. II - Photometric techniques and basic data
Results are presented of photographic surface photometry carried out for305 (mostly dwarf) galaxies in the Virgo cluster, in which the galaxyimages were digitized on 14 of the 67 du Pont plates used for the Virgocluster survey. Azimuthally averaged surface brightness profiles areshown for all galaxies. The following model-free photometric parametersare derived and listed for each galaxy: total apparent blue magnitude,mean effective radius and surface brightness, and various isophotalradii, ellipticity, and position angle. Most galaxies were fitted by anexponential form and/or a King model profile. The best-fittingparameters, including the 'nuclear' (central residual) magnitudes fordE+dS0 galaxies, are listed.
| Neutral hydrogen detection survey of dwarf galaxies. II - Faint Virgo dwarfs and a field sample
Neutral hydrogen spectra are presented for 53 faint dwarf galaxies inVirgo, completing the Arecibo survey of all late-type dwarfs in theVirgo Cluster Catalog, and for 42 dwarf galaxies from the field sampleof Binggeli et al. (1989). For detected galaxies, heliocentricvelocities, profile widths, and single-beam fluxes are tabulated. Thefield sample has been used to investigate the field luminosity functionand the clustering of dwarf galaxies vis-a-vis bright galaxies.
| H I detection survey of a complete magnitude-limited sample of dwarf irregular galaxies in the Virgo Cluster area
New single-beam Arecibo H I observations of 298 late-type galaxies inthe Virgo Cluster drawn mostly from the new catalog of Binggeli,Sandage, and Tammann (1985) are presented. Two hundred seventeen ofthese constitute a magnitude-limited 'complete sample' of such galaxies,types Sdm through Im and BCD. Sixty-one percent of this 'completesample' was detected, greatly enhancing the store of redshifts and H Imasses for such galaxies in the Virgo Cluster. For detected galaxies,heliocentric velocities, 50 percent profile widths, and single-beamfluxes are presented. For those that escaped detection, upper limits arecomputed to the flux appropriate to the redshift range (-600 to +3000km/s).
| 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.
| A catalog of dwarf galaxies in Virgo
A catalog listing the location, apparent angular diameter, type,estimated central light concentration, and estimated brightness of 846dwarf galaxies in a 200-deg-sq region in Virgo is presented. Thegalaxies comprise 634 ellipticals, 137 IC-3475-type galaxies, 73 dwarfspirals and irregulars, and two objects which are jets of normalgalaxies, and were found on nine long-exposure IIIa-J-emulsion platesmade with the 1.2-m-Schmidt telescope at Palomar Observatory from 1971to 1976. Concordances to other catalogs, tables of additionalparameters, maps, graphs, and photographs are provided. The projecteddistributions of normal and dwarf galaxies and the dependence ofapparent luminosity on central light concentration are discussed. It isfound that dwarf ellipticals and IC-3475-type galaxies are probablemembers of the Virgo cluster, while dwarf spirals and possibly dwarfirregulars are not.
| The distribution of Sculptor-type dwarf galaxies.
Not Available
| Dwarf galaxies in the Virgo cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61...69R&db_key=AST
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
Catàlegs i designacions:
|
