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Classification of Spectra from the Infrared Space Observatory PHT-S Database
We have classified over 1500 infrared spectra obtained with the PHT-Sspectrometer aboard the Infrared Space Observatory according to thesystem developed for the Short Wavelength Spectrometer (SWS) spectra byKraemer et al. The majority of these spectra contribute to subclassesthat are either underrepresented in the SWS spectral database or containsources that are too faint, such as M dwarfs, to have been observed byeither the SWS or the Infrared Astronomical Satellite Low ResolutionSpectrometer. There is strong overall agreement about the chemistry ofobjects observed with both instruments. Discrepancies can usually betraced to the different wavelength ranges and sensitivities of theinstruments. Finally, a large subset of the observations (~=250 spectra)exhibit a featureless, red continuum that is consistent with emissionfrom zodiacal dust and suggest directions for further analysis of thisserendipitous measurement of the zodiacal background.Based on observations with the Infrared Space Observatory (ISO), aEuropean Space Agency (ESA) project with instruments funded by ESAMember States (especially the Principle Investigator countries: France,Germany, Netherlands, and United Kingdom) and with the participation ofthe Institute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| Radio emission from AGN detected by the VLA FIRST survey
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.Tables 3 and 4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/35
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Soft X-ray properties of a spectroscopically selected sample of interacting and isolated Seyfert galaxies
We present a catalogue of ROSAT detected sources in the sample ofspectroscopically selected Seyfert 1 and Seyfert 2 galaxies of Rafanelliet al. (\cite{Rafanelli95}). The catalogue contains 102 Seyfert 1 and 36Seyfert 2 galaxies. The identification is based on X-ray contour mapsoverlaid on optical images taken from the Digitized Sky Survey. We havederived the basic spectral and timing properties of the X-ray detectedSeyfert galaxies. For Seyfert 1 galaxies a strong correlation betweenphoton index and X-ray luminosity is detected. We confirm the presenceof generally steeper X-ray continua in narrow-line Seyfert 1 galaxies(NLS1s) compared to broad-line Seyfert 1 galaxies. Seyfert 2 galaxiesshow photon indices similar to those of NLS1s. Whereas a tendency for anincreasing X-ray luminosity with increasing interaction strength isfound for Seyfert 1 galaxies, such a correlation is not found forSeyfert 2 galaxies. For Seyfert 1 galaxies we found also a strongcorrelation for increasing far-infrared luminosity with increasinginteraction strength. Both NLS1s and Seyfert 2 galaxies show the highestvalues of far-infrared luminosity compared to Seyfert 1 galaxies,suggesting that NLS1s and Seyfert 2 galaxies host strong (circumnuclear)star formation. For variable Seyfert galaxies we present the X-ray lightcurves obtained from the ROSAT All-Sky Survey and from ROSAT PSPC andHRI pointed observations. Besides the expected strong short- andlong-term X-ray variability in Seyfert 1 galaxies, we find indicationsfor X-ray flux variations in Seyfert 2 galaxies. All overlays can beretrieved via CDS anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)}or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/368/797
| H I line observations of luminous infrared galaxy mergers
A total of 19 luminous infrared galaxy mergers, with LIR>~ 2 1011 Lsun, for H0=75 kms-1 Mpc-1, have been observed in the H I line atNançay and four of them were observed at Arecibo as well. Ofthese 19, ten had not been observed before. Six were clearly detected,one of which for the first time. The objective was to statisticallysample the H I gas mass in luminous infrared mergers along a starburstmerger sequence where the molecular CO gas content is already known. Wealso searched the literature for H I data and compared these with ourobservations.
| Binary globular clusters
The dynamics of a close binary system of globular clusters isconsidered. It is shown that the star transfer process from one of thecomponents to the other should lead to the decrease of the dimension ofthe first cluster with simultaneous increase of the dimension of thesecond one. The rates of variations of clusters' sizes due to the mutualtidal interaction between the components, as well as of the orbitalrotation of the binary system on the evolution of clusters' sizes, areestimated. The results may be attributed to the double nuclei observedin certain galaxies and to globular clusters in LMC.
| Cold gas and star formation in a merging galaxy sequence
We explore the evolution of the cold gas (molecular and neutralhydrogen) and star formation activity during galaxy interactions, usinga merging galaxy sequence comprising both pre- and post-mergercandidates. Data for this study come from the literature, but aresupplemented by some new radio observations presented here. First, weconfirm that the ratio of far-infrared luminosity to molecular hydrogenmass (LFIRM(H2); star formation efficiency)increases close to nuclear coalescence. After the merging of the twonuclei there is evidence that the star formation efficiency declinesagain to values typical of ellipticals. This trend can be attributed toM(H2) depletion arising from interaction induced starformation. However, there is significant scatter, likely to arise fromdifferences in the interaction details (e.g., disc-to-bulge ratio,geometry) of individual systems. Secondly, we find that the centralmolecular hydrogen surface density, ΣH2,increases close to the final stages of the merging of the two nuclei.Such a trend, indicating gas inflows caused by gravitationalinstabilities during the interaction, is also predicted by numericalsimulations. Furthermore, there is evidence for a decreasing fraction ofcold gas mass from early interacting systems to merger remnants,attributed to neutral hydrogen conversion into other forms (e.g., stars,hot gas) and molecular hydrogen depletion resulting from ongoing starformation. The evolution of the total-radio to blue-band luminosityratio, reflecting the total (disc and nucleus) star formation activity,is also investigated. Although this ratio is on average higher than thatfor isolated spirals, we find a marginal increase along the mergingsequence, attributed to the relative insensitivity of disc starformation to interactions. However, a similar result is also obtainedfor the nuclear radio emission, although galaxy interactions arebelieved to significantly affect the activity (star formation, AGN) inthe central galaxy regions. Nevertheless, the nuclear-radio to blue-bandluminosity ratio is significantly elevated compared with that forisolated spirals. Finally, we find that the FIR-radio flux ratiodistribution of interacting galaxies is consistent with star formationbeing the main energizing source.
| Optical Spectral Signatures of Dusty Starburst Galaxies
We analyze the optical spectral properties of the complete sample ofVery Luminous Infrared Galaxies presented by Wu et al., and we find ahigh fraction (~50%) of spectra showing both a strong Hδ line inabsorption and relatively modest [O II] emission [e(a) spectra]. Thee(a) signature has been proposed as an efficient method to identifydusty starburst galaxies, and we study the star formation activity andthe nature of these galaxies, as well as the effects of dust on theirobserved properties. We examine their emission-line characteristics, inparticular their [O II]/Hα ratio, and we find this to be greatlyaffected by reddening. A search for AGN spectral signatures reveals thatthe e(a) galaxies are typically H II/LINER galaxies. We compare the starformation rates derived from the FIR luminosities with the estimatesbased on the Hα line and find that the values obtained from theoptical emission lines are a factor of 10-70 (Hα) and 20-140 ([OII]) lower than the FIR estimates (50-300 Msolaryr-1). We then study the morphological properties of the e(a)galaxies, looking for a near companion or signs of a merger/interaction.In order to explore the evolution of the e(a) population, we present anoverview of the available observations of e(a) galaxies in differentenvironments both at low and high redshift. Finally, we discuss the roleof dust in determining the e(a) spectral properties and we propose ascenario of selective obscuration in which the extinction decreases withthe stellar age.
| 2.5-11 micron spectroscopy and imaging of AGNs. Implication for unification schemes
We present low resolution spectrophotometric and imaging ISOobservations of a sample of 57 AGNs and one non-active SB galaxy overthe 2.5-11 mu m range. The sample is about equally divided into type I(<= 1.5; 28 sources) and type II (> 1.5; 29 sources) objects. Themid-IR (MIR) spectra of type I (Sf1) and type II (Sf2) objects arestatistically different: Sf1 spectra are characterized by a strongcontinuum well approximated by a power-law of average index < alpha> = -0.84+/-0.24 with only weak emission features from PolycyclicAromatic Hydrocarbon (PAH) bands at 3.3, 6.2, 7.7 and 8.6 mu m. In sharpcontrast to Sf1s, most Sf2s display a weak continuum but very strong PAHemission bands, with equivalent widths (EW) up to 7.2 mu m. On the otherhand, Sf1s and Sf2s do not have statistically different PAH luminositieswhile the 7 mu m continuum is on the average a factor ~ 8 less luminousin Sf2s than in Sf1s. Because the PAH emission is unrelated to thenuclear activity and arises in the interstellar medium of the underlyinggalactic bulge, its EW is a sensitive nuclear redenning indicator. Theseresults are consistent with unification schemes and imply that the MIRnuclear continuum source of Sf2s is, on the average, extinguished by92+/-37 visual magnitudes whereas it is directly visible in Sf1s. Thedispersion in Sf2's PAH EW is consistent with the expected spread inviewing angles. Those Sf2s with EW(PAH) > 5 μm suffer from anextinction Av > 125 magnitudes and are invariablyextremely weak X-ray sources. Such Sf2s presumably represent the highlyinclined objects where our line of sight intercepts the full extent ofthe molecular torus. Conversely, about a third of the Sf2s have PAH EW<= 2 mu m, in the range of Sf1s. Among them, those which have beenobserved in spectropolarimetry and/or in IR spectroscopy invariablydisplay ``hidden'' broad lines. As proposed by Heisler et al.(\cite{heisler}), such Sf2s are most likely seen at grazing incidencesuch that one has a direct view of both the ``reflecting screen'' andthe torus inner wall responsible for the near and mid-IR continuum. Ourobservations therefore constrain the screen and the torus inner wall tobe spatially co-located. Finally, the 9.7 mu m Silicate feature appearsweakly in emission in Sf1s, implying that the torus vertical opticalthickness cannot significantly exceed 1024 cm-2.Based on observations with ISO, an ESA projects with instruments fundedby ESA member states (especially the PI countries: France, Germany, theNetherlands and the United Kingdom) and with the participation of ISASand NASA. Tables 2, 3, 4, 5 are only available in electronic form viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Star formation in distant starburst galaxies
This paper discusses the stellar population content of distant (5 000 kms^{-1} <== V_R<=16 000 km s^{-1}) galaxies with enhancedstar-formation activity. Distinction is made between isolated galaxiesand galaxies morphologically disturbed, with clear signs of interactionsuch as mergers. In these galaxies the International UltravioletExplorer (M_BoxIUE) large aperture samples most of the galaxy's body.Consequently, the resulting integrated spectra arise primarily from bluestellar populations of different ages together with significantcontributions from intermediate and old age components, subject tovarying reddening amounts. Instead of analysing individual, usually lowSignal-to-Noise ratio (S/N) spectra, our approach is to coadd thespectra of objects with similar spectral properties in the UV,considering as well their properties in the visible/near-infraredranges. Consequently, the resulting high (S/N) template spectra containthe average properties of a rather uniform class of objects, andinformation on spectral features can now be analysed with moreprecision. Three groups have been found for the interacting galaxies,corresponding to a red, blue and very blue continuum. Isolated galaxieshave been separated into two groups, one with a flat/red continuum andthe other with a blue continuum. For comparison, we also include in thepresent analysis two groups of nearby disturbed galaxies. Stellarpopulations are analysed by means of a synthesis algorithm based on starcluster spectral components of different ages which fit the observedspectra both in terms of continuum distribution and spectral features.Flux fractions of the different age groups found in the synthesis havebeen transformed into mass fractions, allowing inferences on the starformation histories. Young stellar populations (age <500 Myr) are themain flux contributors, except for the groups with a red spectrum notdue to extinction, arising from the intermediate (age ~1 - 2 Gyr) andold age populations. We also study the reddening values and theextinction law: a Small Magellanic Cloud-like extinction law isappropriate for all cases. As compared to nearby galaxies with enhancedstar-formation, the distant starburst galaxy spectral groups exhibitlarger contributions from the intermediate and old age populations. Thiseffect is mainly accounted for by the larger spatial area sampled by theM_BoxIUE slit in the distant galaxies, including not only the entirebulge but also evolved disk populations. The present results provide aquantitative measure of the star-forming activity in interactinggalaxies, compared to isolated galaxies. Based upon data collected withthe International Ultraviolet Explorer (IUE) Satellite, supported byNASA, SERC and ESA.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Molecular Gas Depletion and Starbursts in Luminous Infrared Galaxy Mergers
Most luminous infrared galaxies (LIGs) are closely interacting/mergingsystems that are rich in molecular gas. Here we study the relationshipbetween the stage of the galaxy-galaxy interactions, the molecular gasmass, and the star formation rate as deduced from the infraredluminosity L_IR in LIGs. We find a correlation between the CO (1-0)luminosity [a measure of molecular mass M(H_2)] and the projectedseparation of merger nuclei (the indicator of merging stages) in asample of 50 LIG mergers, which shows that the molecular gas contentdecreases as merging advances. The starburst is due to enhanced starformation in preexisting molecular clouds and not to the formation ofmore molecular clouds from atomic gas. Because of the starbursts, themolecular content is being rapidly depleted as merging progresses. Thisis further supported by an anticorrelation between L_IR/M(H_2), theglobal measure of the star formation rate per unit gas mass, and theprojected separation that implies an enhanced star formation``efficiency'' in late-stage mergers compared with that of earlymergers. This is the first evidence connecting the depletion ofmolecular gas with starbursts in interacting galaxies.
| A statistical study of the spectra of very luminous IRAS galaxies. II. Spectral and environmental analysis
Spectroscopic observations of a sample of 73 very luminous IRAS galaxies(log(LIR/Lsun)>=11.5 for H0=50 km\s(-1) ; Mpc(-1) ,q0=0.5) from the 2 Jy redshift surveycatalogue were carried out using the 2.16 m telescope at the BeijingAstronomical Observatory. The observational data, including the opticalimages (extracted from Digital Sky Survey) and spectra for thesegalaxies, are presented in Paper I \cite[(Wu et al. 1998)]{wu98}. Inthis paper, we give the spectral and morphological classifications forthese very luminous IRAS galaxies (VLIRGs). We show that about 60% ofVLIRGs exhibit AGN-like spectra (Seyfert 1s, Seyfert 2s, LINER-likegalaxies). This fraction goes up to 82% for the ultraluminous IRASgalaxies (ULIRGs) subsample (Log(LIR/Lsun) >=12.0). 56% of the VLIRGs show strong interaction or merging signatures;this fraction rises to 91% for the ULIRGs. These statistical resultsstrongly suggest that interaction triggers nuclear activities andenhances the infrared luminosity. We find that LINER and a mixture typewhich have optical properties of both HII galaxies and LINERs could beat the transition stage from infrared luminous HII galaxies to AGNs;their main energy production is from starbursts as well as AGNs. Bothinfrared luminosities and Hα equivalent widths increasedramatically as nuclear separations between VLIRGs and their nearestneighbors decrease. There is little doubt that strong starbursts happenin the nuclei of VLIRGs. Assuming class 0 as advanced merger, weconstruct a simple merger sequence, from morphological classes 1 to 4(with near or far companions), to class 5 and 6 (interacting pairs andmergers) and then to class 0 (isolated galaxies). Along this sequence,VLIRGs evolve from HII galaxies to AGNs. Table 1 is only available atthe CDS via anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr
| A statistical study of the spectra of very luminous IRAS galaxies. I. Data
This paper presents the results of spectral observations for the largestcomplete sample of very luminous IRAS galaxies obtained to date. Thesample consists of those 73 objects for which log(L_IR/Lsun)>= 11.5 (H0=50;km; s(-1) Mpc(-1) , q0=0.5) andmag <= 15.5 , and was extracted from the 2 Jy IRAS redshift catalog.All the spectra were obtained using the 2.16 m telescope of BeijingAstronomical Observatory during the years 1994-1996. A total of 123galaxy spectra were obtained with spectral ranges of 4400;Angstroms to7100;Angstroms and 3500;Angstroms to 8100;Angstroms at resolutions of11.2;Angstroms and 9.3;Angstroms respectively. In addition to the 73spectra for sample galaxies, we also present spectra for ten non-samplegalaxies and a further 40 for the companions of sample galaxies. Thedata presented include nuclear spectrum and the parameters describingthe emission lines, absorption lines and continua as well as DSS imagesand environmental parameters. Table 1 is also available in electricform, Table 2-4 are only available in electronic form form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130. 79.128.5) or via http:cdsweb.u-strasbg.fr/Abstract.html. Figures 4 and 9 are published in theon-line version of A&A..
| Optical and Far-Infrared Emission of IRAS Seyfert Galaxies
This paper presents an analysis of moderately large samples of type 1and 2 Seyfert galaxies through optical observations and far-infraredIRAS data, also taking into account theoretical color indices derivedfrom dust emission models. The galaxies in the samples cover a ratherlarge interval in far-infrared luminosity, i.e., 7.6 <= log(LIR/Lȯ) <= 12.6. We show that both types of Seyferts haveapproximately the same distribution of number of objects with a givenLIR. Galaxies with similar far-infrared color indices alpha (100, 60)are grouped together, and the corresponding average color indices areinterpreted in terms of a simple model in which the observed colorsresult from the combination of dust directly heated by the activegalactic nucleus with a component from the host galaxy represented bythe emission of cool dust. On the basis of the average IRAS colors ofthe derived groups, we show that type 1 and 2 Seyfert galaxies areundistinguishable from each other. From the luminosity ratios LIR/LHalpha and LIR/L[O III], we show that basically the same model can beapplied to both types of Seyfert, only allowing for the variation ofmodel conditions: type 2 Seyferts would be like type 1 Seyferts but withthe Seyfert nucleus and broad line region more effectively "hidden" bydust.
| Galactic H i Column Densities toward Quasars and Active Galactic Nuclei
We have determined accurate values of the Galactic neutral hydrogencolumn density, N_H_, toward 220 quasars and active galactic nuclei from21 cm H I measurements made on the 140 Foot Telescope (42.7 m). Accuratevalues of N_H_ have now been obtained for the whole PG bright quasarsample and most quasars that have been observed by ROSAT and the HubbleSpace Telescope through mid-1993. The spectra were corrected for stray21 cm radiation yielding values of NH with a typical uncertainty of 1 x1O^19^ cm^-2^ for high Galactic latitude directions. The H I columndensities will be useful for correcting for interstellar opacity at UVand soft X-ray wavelengths, and for estimating the reddening andextinction toward these objects.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| A multifrequency radio continuum and IRAS faint source survey of markarian galaxies
Results are presented from a multifrequency radio continumm survey ofMarkarian galaxies (MRKs) and are supplemented by IRAS infrared datafrom the Faint Source Survey. Radio data are presented for 899 MRKsobserved at nu = 4.755 GHz with the National Radio Astronomy Observatory(NRAO)-Green Bank 300 foot (91 m) telescope, including nearly 88% ofthose objects in Markarian lists VI-XIV. In addition, 1.415 GHzmeasurements of 258 MRKs, over 30% of the MRKs accessible from theNational Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported.Radio continuum observations of smaller numbers of MRKs were made at10.63 GHz and at 23.1 GHz and are also presented. Infrared data from theIRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, withreasonably secure identifications extracted from the NASA/IPACExtragalactic Database. MRKs exhibit the same canonical infraredcharacteristics as those reported for various other galaxy samples, thatis well-known enhancement of the 25 micrometer/60 micrometer color ratioamong Seyfert MRKs, and a clear tendency for MRKs with warmer 60micrometer/100 micrometer colors to also possess cooler 12 micrometer/25micrometer colors. In addition, non-Seyfert are found to obey thewell-documented infrared/radio luminosity correlation, with the tightestcorrelation seen for starburst MRKs.
| Gas content of infrared luminous markarian galaxies
The atomic and molecular hydrogen gas properties of a complete sample ofMarkarian galaxies with flux density at 60 µm higher than 1.95 Jyare presented. We present the improved far-infrared luminosity functionof Markarian galaxies; and its comparison with other samples. We findthat 40% of the bright IRAS galaxies of far-infrared luminosity higherthan 1010.5 L are Markarian galaxies. There is an absence of correlationbetween HI content of Markarian galaxies and current star formationactivity, implying that star formation in these systems has complexstructure and it is not a simple function of the HI content. On thecontrary, the H2 content of Markarian galaxies is well correlated withstar formation activity. It is argued that tight correlation between HIand H2 contents is a consequence of transformation of atomic hydrogeninto molecular.
| On the excess of physical companions among Seyfert galaxies
The results of a search for close companions in two magnitude limitedsamples (mB less than or equal to 15.5) of 99 Seyfert 1 and98 Seyfert 2 galaxies are presented. It is found that there is an excessof physical companions in both samples of galaxies, compared with twocontrol samples of normal field spiral galaxies. The calculated lowerlimit percentages of physical companions are (12 +/- 3)% and (12 +/- 4)%for Seyfert 1 and Seyfert 2, respectively, while the upper limits on thepercentage of galaxies with physical companions are in the range (0%-5%)in both control samples. The excess is confirmed by analysis of theredshifts for all pairs found in the complete, magnitude limited (B(O)less than or equal to 14.5) CfA sample of Seyfert galaxies.
| Optical imaging and long-slit spectroscopy of Markarian galaxies with multiple nuclei. I - Basic data
Optical CCD images and long-slit spectroscopic data are presented forover 100 Markarian (UV-excess) galaxies reported in early studies topossess multiple optical nuclei or extreme morphological peculiaritiessuggestive of galaxy collisions and mergers. Stacked broad-band imagesare presented with histogram equalization in order to showsimultaneously the nuclei and features at very low surface-brightnesslevels. Morphological properties, luminosities and colors of theintegral systems are given. Photometric and image properties of over 200individual nuclei and giant H II regions have been measured with respectto the local backgrounds in the galaxies using an objective imagefinding algorithm. Labeled contour plots identify the measuredsubcomponents. Two-dimensional spectral data are presented, in additionto intensity profiles along the slit in the light of H-alpha + forbiddenN II emission lines and adjacent continuum. Nuclear emission-linemeasurements, reddening estimates, monochromatic continuum magnitudes,and colors are given.
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| Far-infrared properties of Markarian galaxies with multiple nuclei - Warm dust emission in mergers
An investigation of coadded IRAS data is performed on 187 Markariangalaxies where distinguishing morphological characteristics or multipleoptical nuclei are present. The far-IR properties of Markarian galaxiesare compared to the IRAS Bright Galaxy Sample, and a much higher mediandust temperature is found in the multiple nucleus galaxies, suggestingthat more far-IR luminosity results from active star formation. Bothoptical/UV and far-IR selection techniques are necessary to extractcomplete samples of AGNs since the far-IR two-color plane can miss up to50 percent of the galaxies. A systematic increase in the contribution ofwarm dust emission due to active star formation and AGNs is found in astatistical comparison of merger candidates and other galaxy samples.The assumed nature of precursor galaxies determines the assumedenhancement of far-IR luminosity caused by galaxy collisions. A model ispresented which describes the properties of the Markarian galaxies interms of enhanced OB star formation and different grain sizedistributions. The results of the investigation are shown to beconsistent with a 'subdued' interpretation of merging galaxies with highluminosities.
| An 18-cm OH and 21-cm H I survey of luminous far-infrared galaxies. II - H I properties
As a part of the present 18-cm OH and 21-cm H I survey of luminousfar-infrared galaxies, the paper provides H I data obtained at Nancayfor 88 IRAS galaxies, with FIR luminosity above 10 to the 10th solarluminosity. Among them, 64 are measured here for the first time. Whenrestricting to radial velocities smaller than 11,000 km/s, the detectionrate is equal to 85 percent, independent of the distance. These galaxiesappear as giant ones in dimension, total mass and total blue luminosity.All these parameters increase with increasing FIR luminosity. ExtremeFIR luminosity is thus related to gigantism, which could be the resultof mergers. These galaxies are also deficient in their relative H Icontent, in the sense that their global relative H I content issignificantly smaller than in classical galaxies of the Hubble sequence.
| Tests for alignment of galaxy position angles within a sheet of galaxies
Measured position angles of 149 galaxies that lie in a sheet near thevoid in Corona Borealis are presented. The distribution of positions andposition angles is tested for alignment; none is detected.
| X-ray and infrared selected active galactic nuclei. I - The missing edge-on galaxies
Morphological classification and axial ratio measurements for a sampleof 288 Seyfert Galaxies (SGs) are presented. Seyferts are predominantlyspirals, and a deficiency of edge-on objects is found of both classesSeyfert 1 and 2 in comparison with a sample of 1600 normal spirals. Thedata suggest that obscuration extends beyond line region, and that thedistribution of dust is flattened and coplanar with the disk of theparent galaxy. A way to find the missing edge-on SGs on the basis oftheir infrared and X-ray emission is proposed. A sample of 144 IRASgalaxies lying inside or close to unidentified hard X-ray HEAO-1 sourcesis selected. Most of the target galaxies are in fact seen edge-on, andit is estimated that at least about 34 of them are obscured activegalactic nuclei (AGN) associated with the X-ray sources.
| High-luminosity IRAS galaxies. II - Optical spectroscopy, modelling of starburst regions and comparison with structure
Moderate-resolution spectrophotometry was used to obtain variousemission-line ratios and emission-line luminosities for a completesample of predominantly high-luminosity IRAS galaxies. Most of theobjects exhibit H II region-like spectra, while about 12 percent areSeyferts or LINERs. The results show the IRAS galaxies to be of lowerionization than an optically selected sample of H II region-likegalaxies, possibly due to either high metallicities or to their highdust content. Although the estimated number of O stars present isconsistent with the observed emission-line flux, the IR to emission-lineluminosity ratio of all the IRAS galaxies is very high. The presentobservations can be reconciled using a model with two types of regions,type I clouds (with extinctions of about 20) representing very recentstar formation, and type II clouds (with extinctions of about 1)representing older starburst and/or general disk star formation.
| High-luminosity IRAS galaxies. I - The proportion of IRAS galaxies in interacting systems
An analysis of CCD images of a sample of 60 high-luminosity IRASgalaxies from the redshift survey of Lawrence et al. (1986) and of acontrol sample of 87 optically selected galaxies from the Durhamredshift survey (Peterson et al., 1986) is presented. It is found that18 + or - 5 percent of the optically selected galaxies are interactingor merging systems, and that 11 + or - 8 percent of the low-luminosityIRAS galaxies are interacting or merging. At high luminosities, theproportion is shown to be 46 + or - 12 percent. The results suggest thatalthough galaxy interaction is a common causal factor in luminous IRactivity, it is far from being the ubiquitous factor suggested in recentreports.
| Groups of galaxies in the Center for Astrophysics redshift survey
By applying the Huchra and Geller (1982) objective group identificationalgorithm to the Center for Astrophysics' redshift survey, a catalog of128 groups with three or more members is extracted, and 92 of these areused as a statistical sample. A comparison of the distribution of groupcenters with the distribution of all galaxies in the survey indicatesqualitatively that groups trace the large-scale structure of the region.The physical properties of groups may be related to the details oflarge-scale structure, and it is concluded that differences among groupcatalogs may be due to the properties of large-scale structures andtheir location relative to the survey limits.
| A catalogue of Seyfert galaxies.
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