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An IRAS High Resolution Image Restoration (HIRES) Atlas of All Interacting Galaxies in the IRAS Revised Bright Galaxy Sample
The importance of far-infrared observations for our understanding ofextreme activity in interacting and merging galaxies has beenillustrated by many studies. Even though two decades have passed sinceits launch, the most complete all-sky survey to date from which far-IRselected galaxy samples can be chosen is still that of the InfraredAstronomical Satellite (IRAS). However, the spatial resolution of theIRAS all-sky survey is insufficient to resolve the emission fromindividual galaxies in most interacting galaxy pairs, and hence previousstudies of their far-IR properties have had to concentrate either onglobal system properties or on the properties of very widely separatedand weakly interacting pairs. Using the HIRES image reconstructiontechnique, it is possible to achieve a spatial resolution ranging from30" to 1.5m (depending on wavelength and detector coverage), whichis a fourfold improvement over the normal resolution of IRAS. This issufficient to resolve the far-IR emission from the individual galaxiesin many interacting systems detected by IRAS, which is very importantfor meaningful comparisons with single, isolated galaxies. We presenthigh-resolution 12, 25, 60, and 100 μm images of 106 interactinggalaxy systems contained in the IRAS Revised Bright Galaxy Sample (RBGS,Sanders et al.), a complete sample of all galaxies having a 60 μmflux density greater than 5.24 Jy. These systems were selected to haveat least two distinguishable galaxies separated by less than threeaverage galactic diameters, and thus we have excluded very widelyseparated systems and very advanced mergers. Additionally, some systemshave been included that are more than three galactic diameters apart,yet have separations less than 4' and are thus likely to suffer fromconfusion in the RBGS. The new complete survey has the same propertiesas the prototype survey of Surace et al. We find no increased tendencyfor infrared-bright galaxies to be associated with other infrared-brightgalaxies among the widely separated pairs studied here. We find smallenhancements in far-IR activity in multiple galaxy systems relative toRBGS noninteracting galaxies with the same blue luminosity distribution.We also find no differences in infrared activity (as measured byinfrared color and luminosity) between late- and early-type spiralgalaxies.
| Star Formation Rates in Interacting Starburst Galaxies
By narrowband imaging in Hα and in the adjacent red stellarcontinuum we have studied the rate and distribution of star formation in43 systems of luminous and ultraluminous IR galaxies currentlyundergoing interaction and merging. These galaxies are amongst the mostluminous at 60 μm and range in distance from ~50 up to 100 Mpc. Herewe present the Hα and the adjacent red-continuum narrowbandimages, and we compare the star formation rates derived from Hαwith those estimated from the IR luminosity. We find clear evidence forsubstantial extinction and obscuration of star-forming regions in theoptical. Without correction for reddening in the host galaxy orcorrection for [N II] contamination, the star formation rates derivedfor Hα are typically 0.5-1.0 dex lower than those estimated fromthe IR flux, and the scatter in the correlation is very large. However,an unexpected result is that when spectroscopic data are used toeliminate objects dominated by an active nucleus, to determine thegalaxian extinction, and to correct the Hα flux for both reddeningand for the contamination by the [N II] emission, a remarkably goodcorrelation emerges between the star formation rates estimated from theHα flux and those derived from the FIR continuum. In addition, astrong correlation is found between the extinction in the line-emittingregion, AHα, and the rate of star formation. Ourresults invalidate the use of Hα imaging as a reliable indicatorof star formation in starburst galaxies unless spectroscopic data arealso available. This has important implications for the determination ofstar formation rates in high-redshift galaxies. Finally, we find nocorrelation between the measured star formation rates, and theinteraction class, suggesting that the enhanced star formation ratestriggered by the interaction continue throughout the whole of themerging sequence.
| Southern Isolated Galaxy Triplets
Seventy-six isolated triple systems of galaxies with declinatiosnδ<-3° were selected using ESO/SERC and POSS-I sky surveydata. The equatorial coordinates, configuration types, angular sizes,component angular separations, component morphological types, totalmagnitudes, and other parameters are reported for each triplet.Radial-velocity estimates are available for all components in 33 of the76 triplets. The median values of the main dynamicalparametersradial-velocity dispersion, mean harmonic radius,absolute magnitudes of member galaxies, and mass-to-luminosityratiosare similar to those obtained earlier for 83 isolatedtriple systems with δ>-3°.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| Spectroscopic observations of Arp-Madore interacting galaxies. I - Pairs of comparably sized galaxies
Nuclear spectra of 129 galaxies from a sample of 71 pairs of interactingdoubles of comparably sized galaxies have been analyzed on the basis ofIRAS observations. Data obtained include radial velocities, relativeemission-line intensity measurements, and optical classifications. It isconfirmed that a large number of these objects are indeed showing H IIregion type spectra. It is suggested that a low LINER detection ratecould be due to the IR criteria which favor a strong H II region typeactivity and make it difficult to detect low-level LINER activity whichmay be present. The excess of Seyfert-type nuclei was not found, and thereason remains unclear. A high-frequency of one-sided enhancedstar-formation activity, suggested by the far-infrared study of the samesample of galaxies, also was not found. The enhancement of thestar-formation activity more likely to take place in both galaxies, butthe strength and/or time-scale and phase of the activity in each of thetwo galaxies of the pair may differ substantially.
| IRAS LRS spectroscopy of galaxies
The study presents IRAS LRS data for 350 galaxies with pointlike IRASsources having either S(12) or S(25) not less than 1.5 Jy. Techniquesare presented which form the mean of an ensemble of LRS spectra, ll ofwhich are only of low signal-to-noise ratio, by quantitative evaluationof the significance of the individual spectra for each object ratherthan mere acceptance of the 'average spectrum' present in the completeLRS data base. Average LRS spectra for groups of galaxies with distinctoptical nuclear properties are formed. Average LRS spectra for severalcategories of objects are presented and interpreted. H II regiongalaxies show the polycyclic aromatic hydrocarbon spectrum of bands inemissions; type 2 Seyferts present a broad emission feature parking near16 microns; LINERs and galaxies without optical emission lines have LRSspectra that decline with wavelength, whereas type 1 Seyferts and WRgalaxies have red spectra suggestive of nonthermal emission processes.
| Infrared properties of interacting IRAS galaxies
This paper presents near-infrared photometry and coadded IRAS data for asample of 19 interacting and merging galaxy systems selected by IRASflux and morphological criteria. The far-infrared activity LFIR/LB riseswith interaction strength. There are also changes in the far-infraredcolors: log(f12/f25) is lower and log(f60/f100) higher for stronginteractions. This behavior can be understood in the context oftwo-component models of the far-infrared emission as an increase in thecontribution of active star formation to the infrared activity. Thenear-infrared colors of the galaxies are studied, and the use of K-Lcolor excesses to search for far-infrared emission is justified. Thedistribution of infrared activity in binary galaxies is analyzed withthe help of K-L color excesses and confirmed using IRAS data. Contraryto some earlier studies, it is found that enhanced activity in bothcomponents of an interacting system is frequent. The implications ofthis behavior for the conditions necessary to trigger starbursts arediscussed. The occurrence of a significant number of systems withinfrared activity in both galaxies suggests that disturbances of thegaseous component leading to starbursts may be less sensitive to therelative orientation of the interacting galaxies than disturbances ofthe stellar component leading to prominent tidal tails.
| Long slit spectroscopy of emission line galaxies. II - Physical properties of the ionized gas and general characteristics
A physical interpretation is given to long-slit spectroscopic data for16 extended ionized envelopes surrounding different types of AGNpresented in a previous paper. Ionization mechanisms are discussed,comparing reddened emission line ratios to published hot-ionization andshock ionization models. High ionization emission lines can be accountedfor by photoionization by a nonstellar UV continuum, whilelow-ionization emission lines are better accounted for when shocks areincluded. Detailed physical properties are derived for a number ofextranuclear regions show that the gas is always clumpy with typicalfilling factors of a few 0.01. A correlation is found between themaximum extent of the ionized gas and the UV luminosity at the Lymanlimit. For a large sample of nebulosities gathered from the literature,correlations are found between phi(max) and the absolute magnitude andbetween phi(max) and the radio power.
| A catalogue of extended ionized nebulosities around active galactic nuclei
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989A&AS...81..253D&db_key=AST
| A catalogue of Seyfert galaxies.
Not Available
| Long slit spectroscopy of emission line galaxies. I - The sample
Optical long slit spectroscopic observations have been made for 15emission line galaxies with nuclei showing a sequence of activity levelsin the radio, X-ray, and/or optical ranges. The existence of extendedionized envelopes has been found for the first time for about half ofthe galaxies considered, including low-ionization-level nebulositiesaround two Seyfert type-1 nucleii. The main properties of each galaxy atdifferent wavelengths are presented, along with the observed lineintensities for the nuclei and for several extranuclear regions. Thereddening corrections to be applied are discussed, and electronictemperatures and densities are given where possible.
| Imaging of the ionized gas and stars in emission line galaxies
Broad-band and narrow-band (mainly H-alpha and forbidden O III)observations of 11 galaxies with differing types of nuclear activity,obtained using a CCD imaging system on the 1.5-m Danish telescope at ESOduring December 1983 and August 1984, are reported. The data arepresented in tables and isophote maps and characterized in detail. Nineof the galaxies are shown to have diffuse ionized nebulosity extendingbeyond the spiral arms; the size of the nebulosity increases with thegalactic optical and UV luminosity but does not depend on the level ofnuclear activity or the radio loudness. It is inferred that extendedcloud structures may result from intergalactic tidal interactions, andthat in each galaxy the ionization mechanisms in the narrow-line regionand the nebulosity are the same.
| Southern Galaxy Catalogue.
Not Available
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