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Supernovae 2006es, 2006et, 2006eu
IAUC 8745 available at Central Bureau for Astronomical Telegrams.
| An Integrated Spectrophotometric Survey of Nearby Star-forming Galaxies
We present integrated optical spectrophotometry for a sample of 417nearby galaxies. Our observations consist of spatially integrated,S/N=10-100 spectroscopy between 3600 and 6900 Å at ~8 Å FWHMresolution. In addition, we present nuclear (2.5"×2.5")spectroscopy for 153 of these objects. Our sample targets a diverserange of galaxy types, including starbursts, peculiar galaxies,interacting/merging systems, dusty, infrared-luminous galaxies, and asignificant number of normal galaxies. We use population synthesis tomodel and subtract the stellar continuum underlying the nebular emissionlines. This technique results in emission-line measurements reliablycorrected for stellar absorption. Here we present the integrated andnuclear spectra, the nebular emission-line fluxes and equivalent widths,and a comprehensive compilation of ancillary data available in theliterature for our sample. In a series of subsequent papers we use thesedata to study optical star formation rate indicators, nebular abundancediagnostics, the luminosity-metallicity relation, the dust properties ofnormal and starburst galaxies, and the star formation histories ofinfrared-luminous galaxies.
| Multiwavelength Star Formation Indicators: Observations
We present a compilation of multiwavelength data on different starformation indicators for a sample of nearby star forming galaxies. Herewe discuss the observations, reductions and measurements of ultravioletimages obtained with STIS on board the Hubble Space Telescope (HST),ground-based Hα, and VLA 8.46 GHz radio images. These observationsare complemented with infrared fluxes, as well as large-apertureoptical, radio, and ultraviolet data from the literature. This databasewill be used in a forthcoming paper to compare star formation rates atdifferent wave bands. We also present spectral energy distributions(SEDs) for those galaxies with at least one far-infrared measurementsfrom ISO, longward of 100 μm. These SEDs are divided in two groups,those that are dominated by the far-infrared emission, and those forwhich the contribution from the far-infrared and optical emission iscomparable. These SEDs are useful tools to study the properties ofhigh-redshift galaxies.Based on observations made with the NASA/ESA Hubble Space Telescope,which is operated by the Association of Universities for Research inAstronomy, Inc., under NASA contract NAS5-26555.Based on observations obtained with the Apache Point Observatory 3.5 mtelescope, which is owned and operated by the Astrophysical ResearchConsortium.
| Ultraviolet-to-Far-Infrared Properties of Local Star-forming Galaxies
We present the results of a multiwavelength study of nearby galaxiesaimed at understanding the relation between the ultraviolet andfar-infrared emission in star-forming galaxies. The data set comprisesnew ultraviolet (from HST STIS), ground-based Hα, and radiocontinuum observations, together with archival infrared data (from IRASand ISO). The local galaxies are used as benchmarks for comparison ofthe infrared-to-ultraviolet properties with two populations ofhigh-redshift galaxies: the submillimeter star-forming galaxies detectedby SCUBA and the ultraviolet-selected Lyman break galaxies (LBGs). Inaddition, the long wavelength baseline covered by the present dataenables us to compare the star formation rates (SFRs) derived from theobserved ultraviolet, Hα, infrared, and radio luminosities and togauge the impact of dust opacity in the local galaxies. We also derive anew calibration for the nonthermal part of the radio SFR estimator,based on the comparison of 1.4 GHz measurements with a new estimator ofthe bolometric luminosity of the star-forming regions. We find that moreactively star-forming galaxies show higher dust opacities, which is inline with previous results. We find that the local star-forming galaxieshave a lower Fλ(205 μm)/Fλ(UV)ratio by 2-3 orders of magnitude than the submillimeter-selectedgalaxies and may have a similar or somewhat higherFλ(205 μm)/Fλ(UV) ratio thanLBGs. The Fλ(205 μm)/Fλ(UV) ratioof the local galaxy population may be influenced by the cool dustemission in the far-infrared heated by nonionizing stellar populations,which may be reduced or absent in the LBGs.Based on observations made with the NASA/ESA Hubble Space Telescope,which is operated by the Association of Universities for Research inAstronomy, Inc., under NASA contract NAS5-26555.Based on observations obtained with the Apache Point Observatory 3.5 mtelescope, which is owned and operated by the Astrophysical ResearchConsortium.
| 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).
| 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.
| COLA. II. Radio and Spectroscopic Diagnostics of Nuclear Activity in Galaxies
We present optical spectroscopic observations of 93 galaxies taken fromthe infrared-selected COLA (compact objects in low-power AGNs) sample.These are all galaxies for which we have previously obtainedlow-resolution radio observations and high-resolution (<0.05")Australian Long Baseline Array snapshots. The sample spans the range offar-IR luminosities from normal galaxies to luminous infrared galaxiesand contains a significant number of galaxies involved in galaxy-galaxyinteractions. Of the galaxies observed, 78 (84%) exhibit emission linesindicating that they are either AGNs or actively forming stars(starburst galaxies). Using a newly developed, theoretically based,optical emission line scheme to classify the spectra, we find that 15%of the emission-line galaxies are Seyfert galaxies, 77% are starbursts,and the rest are either borderline AGN/starburst or show ambiguouscharacteristics. We find little evidence for an increase in the fractionof AGNs in the sample as a function of far-IR (FIR) luminosity, incontrast to previous studies, but our sample covers only a small rangein infrared luminosity(1010.5Lsolar<=LFIR<=1011.7 Lsolar), and thus a weak trend may be masked. Instead,as the infrared luminosity increases, so does the fraction of metal-richstarbursts, objects that on more traditional diagnostic diagrams wouldhave been classified as weak, low-ionization, narrow emission lineregions. As a whole the Seyfert galaxies exhibit a small, butstatistically significant, radio excess on the radio-FIR correlationcompared to the galaxies classified as starbursts. Compact (<0.05")radio cores are detected in 55% of the Seyfert galaxies, and thesegalaxies exhibit a significantly larger radio excess than the Seyfertgalaxies in which compact cores were not detected. Our results indicatethat there may be two distinct populations of Seyfert galaxies,``radio-excess'' Seyfert galaxies, which exhibit extended radiostructures and compact radio cores, and ``radio-quiet'' Seyfertgalaxies, in which the majority of the radio emission can be attributedto star formation in the host galaxy. No significant difference is seenbetween the IR and optical spectroscopic properties of Seyfert galaxieswith and without radio cores.
| The IRAS Revised Bright Galaxy Sample
IRAS flux densities, redshifts, and infrared luminosities are reportedfor all sources identified in the IRAS Revised Bright Galaxy Sample(RBGS), a complete flux-limited survey of all extragalactic objects withtotal 60 μm flux density greater than 5.24 Jy, covering the entiresky surveyed by IRAS at Galactic latitudes |b|>5°. The RBGS includes629 objects, with median and mean sample redshifts of 0.0082 and 0.0126,respectively, and a maximum redshift of 0.0876. The RBGS supersedes theprevious two-part IRAS Bright Galaxy Samples(BGS1+BGS2), which were compiled before the final(Pass 3) calibration of the IRAS Level 1 Archive in 1990 May. The RBGSalso makes use of more accurate and consistent automated methods tomeasure the flux of objects with extended emission. The RBGS contains 39objects that were not present in the BGS1+BGS2,and 28 objects from the BGS1+BGS2 have beendropped from RBGS because their revised 60 μm flux densities are notgreater than 5.24 Jy. Comparison of revised flux measurements forsources in both surveys shows that most flux differences are in therange ~5%-25%, although some faint sources at 12 and 25 μm differ byas much as a factor of 2. Basic properties of the RBGS sources aresummarized, including estimated total infrared luminosities, as well asupdates to cross identifications with sources from optical galaxycatalogs established using the NASA/IPAC Extragalactic Database. Inaddition, an atlas of images from the Digitized Sky Survey with overlaysof the IRAS position uncertainty ellipse and annotated scale bars isprovided for ease in visualizing the optical morphology in context withthe angular and metric size of each object. The revised bolometricinfrared luminosity function, φ(Lir), forinfrared-bright galaxies in the local universe remains best fit by adouble power law, φ(L)~Lα, withα=-0.6(+/-0.1) and α=-2.2(+/-0.1) below and above the``characteristic'' infrared luminosityL*ir~1010.5Lsolar,respectively. A companion paper provides IRAS High Resolution (HIRES)processing of over 100 RBGS sources where improved spatial resolutionoften provides better IRAS source positions or allows for deconvolutionof close galaxy pairs.
| The infrared supernova rate in starburst galaxies
We report the results of our ongoing search for extincted supernovae(SNe) at near-infrared wavelengths. We have monitored at 2.2 mu m asample of 46 Luminous Infrared Galaxies and detected 4 SNe. The numberof detections is still small but sufficient to provide the firstestimate of supernova rate at near-infrared wavelengths. We measure a SNrate of SNNIR_r=7.6+/- 3.8 SNu which is an order of magnitudelarger than observed in quiescent galaxies. On the other hand, theobserved near-infrared rate is still a factor 3-10 smaller than thatestimated from the far-infrared luminosity of the galaxies. Amongvarious possibilities, the most likely scenario is that dust extinctionis so high (AV>30) to obscure most SNe even in thenear-IR.The role of type Ia SNe is also discussed within this context. We derivethe type Ia SN rate as a function of the stellar mass of the galaxy andfind a sharp increase toward galaxies with higher activity of starformation. This suggests that a significant fraction of type Ia SNe areassociated with young stellar populations.Finally, as a by-product, we give the average K-band light curve ofcore-collapse SNe based on all the existing data, and review therelation between SN rate and far-infrared luminosity.Based on observations collected at the European Southern Observatory,Chile (proposal 66.B-0417), at the Italian Telescopio Nazionale Galileo(TNG) operated on the island of La Palma by the Centro Galileo Galileiof the INAF (Istituto Nazionale di Astrofisica), and at the StewardObservatory 61'' telescope.
| 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.
| The Far-Infrared Energy Distributions of Seyfert and Starburst Galaxies in the Local Universe: Infrared Space Observatory Photometry of the 12 Micron Active Galaxy Sample
New far-infrared photometry with ISOPHOT aboard the Infrared SpaceObservatory (ISO) is presented for 58 galaxies with homogeneouspublished data for another 32 galaxies, all belonging to the 12 μmgalaxy sample-in total, 29 Seyfert 1 galaxies, 35 Seyfert 2 galaxies,and 12 starburst galaxies, or about half of the 12 μm active galaxysample, plus 14 normal galaxies for comparison. ISO and InfraredAstronomical Satellite (IRAS) data are used to define color-colordiagrams and spectral energy distributions (SEDs). Thermal dust emissionat two temperatures (one cold at 15-30 K and one warm at 50-70 K) canfit the 60-200 μm SED, with a dust emissivity law proportional to theinverse square of the wavelength. Seyfert 1 galaxies and Seyfert 2galaxies are indistinguishable longward of 100 μm, while, as alreadyseen by IRAS, the former have flatter SEDs shortward of 60 μm. A mildanticorrelation is found between the [200-100] color and the ``60 μmexcess.'' We infer that this is due to the fact that galaxies with astrong starburst component and thus a strong 60 μm flux have asteeper far-infrared turnover. In non-Seyfert galaxies, increasing theluminosity corresponds to increasing the star formation rate, whichenhances the 25 and 60 μm emission. This shifts the peak emissionfrom around 150 μm in the most quiescent spirals to shorter than 60μm in the strongest starburst galaxies. To quantify these trendsfurther, we identified with the IRAS colors three idealized infraredSEDs: pure quiescent disk emission, pure starburst emission, and pureSeyfert nucleus emission. Even between 100 and 200 μm, the quiescentdisk emission remains much cooler than the starburst component. Seyfertgalaxies have 100-200 μm SEDs ranging from pure disks to purestarbursts, with no apparent contribution from their active nuclei atthose wavelengths. Based on observations with ISO, an ESA project withinstruments funded by ESA Member States (especially the PI countries:France, Germany, the Netherlands, and the United Kingdom) with theparticipation of ISAS and NASA.
| First Results from the COLA Project: The Radio-Far-Infrared Correlation and Compact Radio Cores in Southern COLA Galaxies
We present the first results from the COLA (compact objects in low-powerAGNs) project, which aims to determine the relationship between onefacet of AGN activity, the compact radio core, and star formation in thecircumnuclear region of the host galaxy. This will be accomplished bythe comparison of the multiwavelength properties of a sample of AGNswith compact radio cores to those of a sample of AGNs without compactcores and a matched sample of galaxies without AGNs. In this paper wediscuss the selection criteria for our galaxy samples and present theinitial radio observations of the 107 southern(δ<0deg) galaxies in our sample. Low-resolution ATCAobservations at 4.8, 2.5, and 1.4 GHz and high-resolution,single-baseline snapshots at 2.3 GHz with the Australian Long BaselineArray (LBA) are presented. We find that for the majority of the galaxiesin our sample, the radio luminosity is correlated with the far-infrared(FIR) luminosity. However, a small number of galaxies exhibit a radioexcess causing them to depart from the FIR-radio correlation. Compactradio cores are detected at fluxes greater than 1.5 mJy in nine of the105 galaxies observed with the LBA. The majority (8/9) of these galaxiesexhibit a radio excess, and 50% (7/14) of the galaxies that lie abovethe radio-FIR correlation by more than 1 σ have compact radiocores. The emission from the compact cores is too weak to account forthis radio excess, implying that there are radio structures associatedwith the compact cores that extend farther than the 0.05" resolution(corresponding to a linear scale 11-22 pc) of the LBA. There is noevidence that the radio luminosity of the compact cores is correlatedwith the FIR galaxy luminosity, indicating that the core contributeslittle to the overall FIR emission of the galaxy. The galaxies withcompact cores tend to be classified optically as AGNs, with two-thirds(6/9) exhibiting Seyfert-like optical emission line ratios, and theremaining galaxies classified either as composite objects (2/9) orstarburst (1/9). The galaxies classified optically as AGNs also exhibitthe largest radio excesses, and we therefore conclude that a large radioexcess on the radio-FIR correlation is a strong indication of an AGNwith a compact radio core.
| Starburst or Seyfert? Adding a Radio and Far-Infrared Perspective to the Investigation of Activity in Composite Galaxies
It was once common to regard Seyfert and starburst galaxies ascompletely different types of object, but there is growing recognitionthat these classifications refer to the extremes of a continuousspectrum of galaxy types. In a previous study we investigated a sampleof galaxies with ambiguous optical emission-line ratios and concludedfrom near-infrared spectroscopic observations that the sample consistedof composite galaxies, containing both a starburst and an activegalactic nucleus (AGN). We now extend our study using radio synthesisand long-baseline interferometer observations made with the AustraliaTelescope, together with far-infrared IRAS observations, to discuss therelative contribution of starburst and AGN components to the overallluminosity of the composite galaxies. We find that only a small fractionof the radio emission (<10%) can be attributed to an AGN and that themajority of the far-infrared emission (>90%) is probably due to thestarburst component. We also show that an AGN contribution to theoptical emission of as little as 10% is sufficient to account for theambiguous line-ratio diagnostics.
| Surface photometry of binary galaxies.
Not Available
| A neutral hydrogen survey of polar ring galaxies. III. Nançay observations and comparison with published data
A total of 50 optically selected polar ring galaxies, polar ring galaxycandidates and related objects were observed in the 21-cm H i line withthe Nançay decimetric radio telescope and 31 were detected. Theobjects, selected by their optical morphology, are all north ofdeclination -39o, and generally relatively nearby (V< 8000km s-1) and/or bright (mB< 15.5). The H i linedata are presented for all 74 galaxies observed for the survey with theEffelsberg, Green Bank or Nanç radio telescopes, as well as allother published H i line parameters of these objects. Three objects wereobserved and detected by us at Parkes. A total of 59 objects weredetected. For each object a brief description is given based on aliterature search.
| Starburst or Seyfert? Using Near-Infrared Spectroscopy to Measure the Activity in Composite Galaxies
We present near-infrared spectra for a sample of galaxies with ambiguousoptical emission-line ratios. These galaxies fall between starbursts andSeyferts in the usual optical diagnostic diagrams. We find a similarresult with the near-infrared emission-line ratios, which suggests thatthe galaxies are composite, containing both a starburst and an AGNcomponent. Furthermore, CO absorption, produced in late-type stars, isdetected within the sample, although at a weaker level than is typicalfor starburst galaxies. We conclude that the CO feature is being dilutedby a contribution from an AGN, thereby confirming the composite natureof these galaxies.
| The Supernova Rate in Starburst Galaxies
We conducted an optical CCD search for supernovae in a sample of 142bright [m(B) <= 16 mag], nearby (z<=0.03) starburst galaxies overthe period 1988 December to 1991 June, to a limiting R-band magnitude of18. Five supernovae were found, in all cases outside the host galaxy'snucleus. We determine supernova rates (in supernova units or SNU) in theextranuclear regions to be 0.7 h^2 SNU for Type Ia, 0.7 h^2 SNU for TypeIb/c, and ~0.6 h^2 SNU for Type II, with large uncertainties but upperlimits of 2.2 h^2, 2.5 h^2, and 1.7 h^2 SNU, respectively. These ratesare similar to those measured in ``normal'' galaxies. We found noevidence for a supernova-induced brightening in any galactic nucleusand, with a few reasonable assumptions, can place upper limits of 9 h^2,12 h^2, and 7 h^2 SNU on the rates of unobscured supernovae Types Ia,Ib/c, and II, respectively, inside the nuclei.
| The Durham/UKST Galaxy Redshift Survey - V. The catalogue
We present the radial velocities and blue, optical magnitudes for all ofthe galaxies within the Durham/UKST Galaxy Redshift Survey. Thiscatalogue consists of ~2500 galaxy redshifts to a limiting apparentmagnitude of B_J⋍17 mag, covering a ~1500-deg^2 area around theSouth Galactic Pole. The galaxies in this survey were selected from theEdinburgh/Durham Southern Galaxy Catalogue and were sampled, in order ofapparent magnitude, at a rate of one galaxy in every three. Thespectroscopy was performed at the 1.2-m UK Schmidt Telescope inAustralia using the FLAIR multi-object spectrograph. We show that ourradial velocity measurements made with this instrument have an empiricalaccuracy of +/-150 km s^-1. The observational techniques and datareduction procedures used in the construction of this survey are alsodiscussed. This survey demonstrates that the UKST can be used to make athree-dimensional map of the large-scale galaxy distribution, via aredshift survey to b_J⋍17 mag, over a wide area of the sky.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| On the morphology of peculiar ring galaxies
It is proposed that peculiar ring galaxies can be divided into fiveprincipal types according to the morphology of the ring and bulge, basedon the visual inspection of 489 selected objects. Those objects havebeen named ``peculiar'' following the ``Catalogue of Southern PeculiarGalaxies and Associations'' by \cite[Arp & Madore (1986]{am6}) Table2 with its notes is only available electronically via anonymous ftp130.79.128.5 or http://cdsweb.u-strasbg.fr.
| 1.25-mm observations of a complete sample of IRAS galaxies. II. Dust properties.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996MNRAS.283...85A&db_key=AST
| Soft X-Ray Properties of Seyfert Galaxies in the ROSAT All-Sky Survey
We present the results of ROSAT All-Sky Survey observations of Seyfertand IR luminous galaxies from the extended 12 micron galaxy sample andthe optically selected CfA sample. Detections are available for 80%(44/55) of the Seyfert 1's and 34% (23/67) of the Seyfert 2's in the 12micron sample, and for 76% (26/34) of the Seyfert 1's and 38% (6/16) ofthe Seyfert 2's in the CfA sample. Roughly half of the Seyfert galaxies(mostly Seyfert 1's) have been fitted to an absorbed power-law model,yielding an average photon index of {GAMMA} = 2.26 +/- 0.11 for 43Seyfert 1's and {GAMMA} = 2.45 +/- 0.18 for 10 Seyfert 2's, with bothtypes having a median value of 2.3. The soft X-ray luminosity correlateswith the 12 micron luminosity, with Seyfert 1's having relatively moresoft X-ray emission than Seyfert 2's of similar mid-IR luminosities by afactor of 1.6 +/- 0.3. Several physical interpretations of these resultsare discussed, including the standard unified model for Seyfertgalaxies. Infrared luminous non- Seyferts are shown to have similardistributions of soft X-ray luminosity and X-ray-to-IR slope as Seyfert2's, suggesting that some of them may harbor obscured active nuclei (ashas already been shown to be true for several objects) and/or that thesoft X-rays from some Seyferts 2's may be nonnuclear. A soft X-rayluminosity function (XLF) is calculated for the 12 micron sample, whichis described well by a single power law with a slope of - 1.75. Thenormalization of this XLF agrees well with that of a hard X-ray selectedsample. Several of our results, related to the XLF and the X- ray-to-IRrelation, are shown to be consistent with the hard X-ray observations ofthe 12 micron sample by Barcons et al.
| Dust and CO emission in normal spirals. I. The data.
We present 1300μm continuum observations and measurements of the CO(1-0) and (2-1) emission from the inner regions of 98 normal galaxies.The spatial resolution ranges from 11" to 45". The sources come from acomplete FIR selected sample of 138 inactive spirals with an opticaldiameter D_25_<=180".
| A CO survey of galaxies with the SEST and the 20-m Onsala telescope.
A large survey of galaxies in the J=1-0 CO line, performed during1985-1988 using the 15-m SEST and the 20-m millimetre wave telescope ofOnsala Space Observatory, is presented. The HPBW of the telescopes are44" and 33" at 115GHz, respectively. The central positions of 168galaxies were observed and 101 of these were detected in the CO line.More than 20% of these are new detections. Maps of some of the galaxiesare also presented.
| The bar-enhanced star-formation activities in spiral galaxies.
We use the ratio L_FIR_/L_B_ and the IRAS color index S_25_/S_12_ (bothwidely used as indices of relative star formation rates in galaxies) toanalyse subsets (containing no known AGNs or merging/interactinggalaxies) of: (a) the IRAS Bright Galaxy Sample, (b) galaxies from theoptically complete RSA sample which have IRAS detections in all fourbands, and (c) a volume-limited IR-unselected sample. We confirm thatIR-bright barred (SB) galaxies do, on average, have very significantlyhigher values of the FIR-optical and S_25_/S_12_ ratios (and presumably,higher relative star formation rates, SFR) than that do unbarred ones;the effect is most obvious in the IR colors. We also confirm that thesedifferences are confined to early-type (S0/a-Sbc) spirals and are notevident among late-type systems (Sc-Sdm). Unlike others, we see noenhancement of the SFR in weakly-barred (SAB) galaxies. We furtherconfirm that the effect of bars on the SFR is associated with therelative IR luminosity and show that it is detectable only in galaxieswith L_FIR_/L_B_>1/3, suggesting that as soon as they have anyeffect, bars translate their host galaxies into this relativelyIR-luminous group. Conversely, for galaxies with L_FIR_/L_B_ below ~0.1this luminosity ratio is lower among barred than unbarred systems, againconfirming and quantifying an earlier result. Although there is nosimple physical relation between H I content and star formation, astrong correlation of H I content with the presence of bars has beenfound for early-type spirals with L_FIR_/L_B_>1/3. This suggests thatthe availability of fuel is the factor determining just which galaxiesundergo bar-induced starbursts.
| Optical Spectroscopy of Luminous Infrared Galaxies. II. Analysis of the Nuclear and Long-Slit Data
A spectroscopic survey of a sample of 200 luminous IRAS galaxies (LIGs:L_ir_^7^ > 3 x 10^10^ L_sun_; H_0_ = 75 km s^-1^ Mpc^-1^) was carriedout using the Palomar 5 meter and University of Hawaii 2.2 m telescopes.Kim et al. (1995) described the data-taking and data-reductionprocedures and presented line and continuum measurements extracted fromthe nucleus of these objects. In this paper, the nuclear data arecombined with circumnuclear measurements on 23 of these galaxies toinvestigate the properties of the line-emitting gas and underlyingstellar population in and out of the nucleus. The nuclear spectra ofthese galaxies were classified as H II region-like" or "AGN-like" usinga large number of line-ratio diagnostics corrected for the underlyingstellar absorption features. This correction is an important source oferrors in some previous studies. The emission-line spectra of many AGNswere found to-be of relatively low ionization level and were thereforeclassified as LINER. We confirm that both the fraction of LIGs with AGNspectra and the fraction of Seyferts among the AGN increase withinfrared luminosity, reaching values of 62% and 54% at the highestobserved luminosities, respectively. The fraction of LINERs, on theother hand, is relatively constant at ~27%. The source of the ionizationof the emission-line gas often is a function of the distance from thenucleus. Based on the emission-line ratios and the strengths of thestellar absorption features, circumnuclear starburst activity is acommon feature of LIGs, regardless of their nuclear spectral types. Theemission-line, absorption-line, continuum, radio, and IRAS properties ofthe LINERs suggest that most of the LINER emission in theseinfrared-selected galaxies is produced through shock ionization ratherthan photoionization by a genuine active nucleus. The nuclear region ofSeyfert LIGs is found to be slightly less reddened than that of theLINERs and H II galaxies. The dust distribution generally isconcentrated toward the nucleus, in agreement with the often peakydistribution of the molecular gas observed in these galaxies. Inverteddust profiles in which the nucleus appears less dusty than thecircumnuclear region are observed in only three LIGs, all of which haveAGN emission-line characteristics (one Seyfert 2 galaxy and two LINERs).Low nuclear dust content appears to favor the detection of activenuclei. This may be due to selection effects or may reflect realphysical differences between these classes of objects: galaxies withSeyfert emission lines may be at a more advanced stage of dustdestruction/expulsion than H II LIGs. Complex optical depth effects mayalso explain these results without invoking a smaller amount of dust inthe nucleus. The Hβ and Mg I b absorption features are stronger inthe nuclei of AGNs (especially among the LINERs) than in H II LIGs,suggesting that AGN LIGs are at a more advanced stage of stellarevolution than H II LIGs. Further support for this scenario comes fromthe fact that AGNs are found more frequently in advanced mergers than HII galaxies (only two Seyfert galaxies are detected in systems withwell-separated nuclei). However, this last result may be a luminosityeffect rather than an effect related to the dominant nuclear source ofionization. Moreover, the absorption-line data may simply reflect thefact that galaxies with powerful H II regions show evidence for youngstars while galaxies with AGNs do not. The radial variations of theHβ and Mg I b absorption features indicate the presence of a strongsource of featureless continuum in the nucleus of nearly all LIGs,regardless of their nuclear spectral types. Contamination by thecircumnuclear starburst prevents us from determining the extent of thiscontinuum source. The [O III] profiles of both Seyfert and LINER LIGswere found to be broader on average than those of H II objects. Nearly20% of the LIGs in our sample have line widths larger than 600 km s^-1^.We find that most of the galaxies in which we could determine the radialvariations of the [O III] line width present broader profiles in thecircumnuclear region than at the nucleus. When combined with publisheddata on a few other well-studied LIGs, these results suggest thatlarge-scale nuclear winds are common in these objects and are anefficient way of getting rid of the obscuring material in the nuclearregion. The spatially extended LINER emission observed in many of theseobjects is probably due to shock ionization resulting from theinteraction of the wind-accelerated gas with the ambient material of thehost galaxy.
| Optical Spectroscopy of Luminous Infrared Galaxies. I. Nuclear Data
A spectroscopic survey of a large sample of luminous infrared galaxies[log (L_ir_/L_sun_)^7^ ~ 10.5-12.5; H_0_ = 75 km s^-1^ Mpc^-1^] has beencarried out using the Palomar 5 m telescope,, and the University ofHawaii 2.2 m telescope. Long-slit spectra covering 375o-8000 A at aresolution of ~10 A were obtained of 200 IRAS galaxies, including 114objects from the IRAS Bright Galaxy Survey, and 86 objects with fainterinfrared fluxes selected on the basis of their "warm" far-infrared(S_60_/S_100_) colors. The methods of observation and data reduction arediscussed. An atlas of the spectra extracted from the nuclear region ofthese objects is presented along with a large number of parametersdescribing the properties of the emission lines, the stellar absorptionlines, and the continuum emission that were measured from the spectra.An analysis of these data is presented in a companion paper (Veilleux etal. 1995) along with a discussion of the spatial variations of theseparameters in a subsample of twenty-three objects.
| Multiwavelength Energy Distributions and Bolometric Luminosities of the 12 Micron Galaxy Sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...453..616S&db_key=AST
| CO, HI and cold dust in a sample of IRAS galaxies.
Using the IRAM 30m, SEST 15m, and Nancay radiotelescopes, we havegathered the 1mm continuum emission, the intensities of the J=1-0 lineof the CO molecule and of the atomic hydrogen line at 21cm for twosamples of IRAS galaxies. The southern sample was selected from the IRASCatalogue and is complete at the limiting flux of 2Jy at 60μm; of the10 northern objects 7 belong to the Smith et al. complete sample (1987)and 3 are isolated objects. Using these data, we have estimated theatomic hydrogen masses from the 21cm emission, the molecular gas massesfrom the CO(1-0)line brightness, and the dust and gas masses from the mmcontinuum emission using two "extreme" dust models. The main conclusionsof this work for far-infrared selected galaxies can be summarized in thefollowing points: (1) the median value of M_H_2__/M_HI_ is 0.5, meaningthat the atomic phase dominates in these galaxies. The fraction of gasin molecular form increases with increasing FIR luminosity but does notshow any obvious trend with other galaxy properties, in particular withthe FIR surface brightness. (2) the H_2_ surface density derived fromCO(1-0)emission is better correlated with the cold dust surface densitythan the HI surface density, but the correlation of HI with dust is notnegligible (we found a correlation coefficient of 0.5, while thecorrelation coefficient with σ_H_2__ is 0.70). Thus, globally inthese galaxies, the cold dust emission is likely associated with boththe molecular and atomic phases. Indeed, the dust surface density isalso correlated with the total gas surface density. (3) the FIR surfacebrightness increases as the third power of the S(60μm) /S(100μm)ratio. It shows a tight correlation with both the H_2_ and dust surfacedensities and a weaker one with the HI surface density. This suggeststhat a large part of the far-infrared emission of these galaxiesoriginates in the molecular medium. (4) the gas-to-dust ratio, (M_H_2__+M_HI_)/M_d_ ranges between 100 and 1000 and its average value is 230,close to the Galactic value. There is indeed a clear trend: this ratiodecreases as the FIR surface density increases. This result can beexplained in the framework of an enhancement of metallicity in galaxydiscs having a higher star formation rate.
| Dust in spiral galaxies, 2
We have mapped 32 non-active spirals at 1300 micrometers and measured 7of them at 450 and 800 micrometers. We determine gas masses, dusttemperatures and IR luminosities. From a detailed analysis we find: (1)The spatial extent of the cold dust is comparable to the optical size ofthe galaxies. About 70% of the mass is contained within half the opticalradius; there the gas surface density decreases inversely proportionalto the galactocentric radius. (2) The new submm data set limits on thedecomposition of the FIR spectra into dust components of differenttemperatures. The flux ratios of 450 to 1300 micrometers suggest twokinds of nonactive spirals: those with S450micrometers/S1300 micrometers approximately equal to40, like the Milky Way, where the coldest dust is approximately 20K andaccounts for most of the emission between 100 and 1300 micrometers; onthe other hand, there are galaxies with S450micrometers/S1300 micrometers approximately 20 whichimplies that most of the interstellar dust is extremely cold(approximately 10 K). (3) The ratio of infrared luminosity to gas mass,LIR/Mgas, equals 5 +/- 2 in solar units. Foractive galaxies from the Markarian catalog this ratio is 20 timeslarger. Therefore LIR/Mgas gives a clear signaturefor the activity stage.
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