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Two-dimensional warm gas kinematics in interacting galaxy systems
Gas reservoirs, internal or acquired, play an important role in thesecular evolution of interacting galaxies, since they are able toenhance/trigger star formation episodes and, probably, feed the activityof active galactic nuclei. Using Fabry-Perot observations, we havemapped, in the Hα line, the warm (T~ 104) gasdistribution and the velocity fields of the galaxy members of fiveinteracting, gas-rich galaxy systems. We investigated two M51-likesystems (Arp 70 and Arp 74), two systems containing highly disruptedmembers (WBL 366 and RR 24) and a case of merging in progress (Arp 299,one of the nearest luminous infrared objects).We detected gas motions following the elongated arm/tail of Arp 70b,while in the fainter member of the pair of galaxies, Arp 70a, the gasdistribution is off-centred with respect to the stellar isophotes,suggesting an external acquisition. Our kinematic data highlightednon-circular motions in the velocity field of one of the members of Arp74 (Arp 74a). The two galaxies of the RR 24 system are connected by onetidal tail, through which the kinematically disturbed component RR 24bseems to supply warm gas to RR 24a. In spite of the nearly irregular gasdistribution and perturbed morphology, WBL 366a (the star-forming galaxyVV-523) and WBL 366b have nearly regular velocity fields. The velocityfield in the Arp 299 system is irregular, and gas flow between the twonuclei is detected.The present observations, discussed in the light of model predictionsand complementary observations from the literature, suggest that allthese systems are still probably in an early phase of the encounter.However, the ionized gas distribution and kinematics are stronglyinfluenced by tidal forces. In particular, cross-fuelling mechanismsbetween galaxies are in action. In Arp 299 the warm and cold gaseouscomponents show similar kinematic properties, although the cold gasseems to maintain a still better organized motion with respect to thewarm gas.
| Hubble Space Telescope Observations of Star-forming Regions in NGC 3994/3995
We obtained ultraviolet and optical images of star-forming regions inthe interacting galaxy system NGC 3994/3995 using the Space TelescopeImaging Spectrograph on the Hubble Space Telescope. We describe thecharacteristics of 56 detected knots, a majority of which are youngerthan 20 Myr old. There is no discernible pattern of knot age withrespect to position within the galaxies. The knots have masses and radiiranging from 7.2×103 to 4.4×106Msolar and from 4 to 23 pc, respectively. Using aconservative criterion, we find that ~15% of these knots may beproto-globular clusters; the percentage of proto-globular clusters maybe as high as ~70%. The UV flux distribution of the knots in NGC 3995can be fitted with a power law with α=-0.72+/-0.11, with noturnover detected brightward of the completeness limit.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS5-26555.
| Revised masses of dust and gas of SCUBA Local Universe Survey far-infrared bright galaxies based on a recent CO survey
Recent CO measurements of an essentially complete subsample of galaxiesfrom the SCUBA Local Universe Survey (SLUGS) are used to examine theirimplications for dust and gas masses in this sample. Estimates of dustmasses are affected by a contribution to the SCUBA brightnessmeasurements by CO(3-2) emission, and molecular gas masses by the use ofa modified value of the CO-to-H2 conversion factor X. Theaverage dust mass is reduced by 25-38 per cent, which has no bearing onearlier conclusions concerning the shape of the dust mass luminosityfunction derived from the SLUGS. The value of X found from the COsurvey, when applied together with the reduction in dust masses, leadsto lower estimates for the mean gas-to-dust mass ratios, where the gasincludes both H2 and H I. For the CO sample, the mean globalratio is reduced from approximately 430 to about 320-360, but is furtherreduced to values near 50 when applied to the nuclear regions relevantto the CO observations. We discuss these results and suggest that thedifferences between the nuclear and outer regions may simply reflectdifferences in metallicity or the existence of considerable amounts ofunobserved cold dust in the outer regions of these galaxies.
| 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.
| H I Observations of Barred Magellanic Spirals. II. The Frequency and Impact of Companions
The results of an H I 21 cm line survey of a sample of Magellanic spiralgalaxies with apparent optical companions reveal that only four of 13systems have confirmed H I-detected neighbors. The current interactionsare affecting the morphology of the main galaxy in only two cases, NGC3664 and NGC 3995. The presence of companions near NGC 2537 and UGC 5391appears to have no effect on the morphology of those galaxies. Overall,there is little difference between the asymmetry of the H I profiles ofthose galaxies with and without companions, and on average, theseMagellanic spirals have H I profiles that are no more asymmetric than arandom sample of spirals in the field. We conclude that currentinteractions cannot be responsible for the lopsided morphology of mostof the galaxies in this sample and that, whatever its original cause,lopsidedness must be a long-lived characteristic of these galaxies.
| Classifications of the Host Galaxies of Supernovae, Set II
Classifications on the DDO system are given for an additional 231 hostgalaxies of supernovae that have been discovered during the course ofthe Lick Observatory Supernova Search with the Katzman Automatic ImagingTelescope (KAIT). This brings the total number of hosts of supernovae(SNe) discovered (or independently rediscovered) by KAIT, which have sofar been classified on a homogeneous system, to 408. The probabilitythat SNe Ia and SNe II have a different distribution of host-galaxyHubble types is found to be 99.7%. A significant difference is alsofound between the distributions of the host galaxies of SNe Ia and ofSNe Ibc (defined here to include SNe Ib, Ib/c, and Ic). However, nosignificant difference is detected between the frequency distributionsof the host galaxies of SNe II and SNe IIn. This suggests that SNe IInare generally not SNe Ia embedded in circumstellar material that aremasquerading as SNe II. Furthermore, no significant difference is foundbetween the distribution of the Hubble types of the hosts of SNe Ibc andof SNe II. Additionally, SNe II-P and SNe II-L are found to occur amongsimilar stellar populations. The ratio of the number of SNe Ia-pec tonormal SNe Ia appears to be higher in early-type galaxies than it is ingalaxies of later morphological types. This suggests that the ancestorsof SNe Ia-pec may differ systematically in age or composition from theprogenitors of normal SNe Ia. Unexpectedly, five SNe of Types Ib/c, II,and IIn (all of which are thought to have massive progenitors) are foundin host galaxies that are nominally classified as types E and S0.However, in each case the galaxy classification is uncertain, or newlyinspected images show evidence suggesting a later classification. Amongthese five objects, NGC 3720, the host galaxy of SN 2002at, wasapparently misidentified in the Carnegie Atlas of Galaxies.
| CO Molecular Gas in Infrared-luminous Galaxies
We present the first statistical survey of the properties of the12CO(1-0) and 12CO(3-2) line emission from thenuclei of a nearly complete subsample of 60 infrared (IR) luminousgalaxies selected from SCUBA Local Universe Galaxy Survey (SLUGS). Thissubsample is flux limited at S60μm>=5.24 Jy with far-IR(FIR) luminosities mostly at LFIR>1010Lsolar. We compare the emission line strengths of12CO(1-0) and (3-2) transitions at a common resolution of~15". The measured 12CO(3-2) to (1-0) line intensity ratiosr31 vary from 0.22 to 1.72, with a mean value of 0.66 for thesources observed, indicating a large spread of the degree of excitationof CO in the sample. These CO data, together with a wide range of dataat different wavelengths obtained from the literature, allow us to studythe relationship between the CO excitation conditions and the physicalproperties of gas/dust and star formation in the central regions ofgalaxies. Our analysis shows that there is a nonlinear relation betweenCO and FIR luminosities, such that their ratioLCO/LFIR decreases linearly with increasingLFIR. This behavior was found to be consistent with theSchmidt law relating star formation rate to molecular gas content, withan index N=1.4+/-0.3. We also find a possible dependence of the degreeof CO gas excitation on the efficiency of star-forming activity. Usingthe large velocity gradient (LVG) approximation to model the observeddata, we investigate the CO-to-H2 conversion factor X for theSLUGS sample. The results show that the mean value of X for the SLUGSsample is lower by a factor of 10 compared to the conventional valuederived for the Galaxy, if we assume the abundance of CO relative toH2, ZCO=10-4. For a subset of 12galaxies with H I maps, we derive a mean total face-on surface densityof H2+HI of about 42 Msolar pc-2 withinabout 2 kpc of the nucleus. This value is intermediate between that ingalaxies like our own and those with strong star formation.
| Tidally Triggered Star Formation in Close Pairs of Galaxies. II. Constraints on Burst Strengths and Ages
Galaxy-galaxy interactions rearrange the baryons in galaxies and triggersubstantial star formation; the aggregate effects of these interactionson the evolutionary histories of galaxies in the universe are poorlyunderstood. We combine B- and R-band photometry and optical spectroscopyto estimate the strengths and timescales of bursts of triggered starformation in the centers of 190 galaxies in pairs and compact groups.Based on an analysis of the measured colors and EW(Hα), wecharacterize the preexisting and triggered populations separately. Thebest-fitting burst scenarios assume stronger reddening corrections forline emission than for the continuum and continuous star formationlasting for >~100 Myr. The most realistic scenarios require aninitial mass function that is deficient in the highest mass stars. Thecolor of the preexisting stellar population is the most significantsource of uncertainty. Triggered star formation contributessubstantially (probably >~50%) to the R-band flux in the centralregions of several galaxies; tidal tails do not necessarily accompanythis star formation. Many of the galaxies in our sample have bluercenters than outskirts, suggesting that pre- or nonmerger interactionsmay lead to evolution along the Hubble sequence. These objects wouldappear blue and compact at higher redshifts; the older, redder outskirtsof the disks would be difficult to detect. Our data indicate thatgalaxies with larger separations on the sky contain weaker, and probablyolder, bursts of star formation on average. However, confirmation ofthese trends requires further constraints on the colors of the olderstellar populations and on the reddening for individual galaxies.
| 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.
| Possibly interacting Vorontsov-Velyaminov galaxies. II. The 6-m telescope spectroscopy of VV 080, 131, 499, 523 and 531
In continuation of the program formulated in Paper I we present resultsof long-slit spectroscopy with the Russian 6-m telescope of five moreobjects from the Vorontsov-Velyaminov (hereafter VV) Atlas and Catalogueof Interacting galaxies. These are the galaxies for which theinteraction is not evident, although all of them are classified asmultiple systems (usually as ``nests'', ``chains'' and similar systems).The spectrophotometry data enable us to derive for all galaxiesabundances of O, and for some of them abundances of N, Ne and S. For twoof them chemical abundances are given for the first time. In spectra ofthree of the studied galaxies [O Iii] lambda 4363 line is measured, andT_e and oxygen abundance are derived by the classical method. For thetwo others, empirical methods are used. For all 5 galaxies, the radialvelocity distribution along the slit was obtained in the Hα -line.The studied galaxies represent a rather mixed sample: from very lowluminosity irregular galaxies, like VV 499 (DDO 053), to rather brightVV 523 (NGC 3991). Their metallicities vary from Z ~ 1/25Zsun for VV 499 to ~ 1/2 Zsun for VV 523. Themorphology of these galaxies ranges between typical dIrr (VV 080)through ring-like (VV 131) to clumpy Irr (VV 523). Position-Velocitydiagrams in the Hα -line along the galaxy body imply the existenceof large-scale ionized gas outflows/supershells around the sites ofintense current and/or recent SF activity. Sizes of supershells vary inthe range of several hundred pc to ~ 2 kpc. For all studied galaxies weexamine their local environment and indicate the nearest neighbouringobjects capable of inducing the observed enhanced star formation.
| SCUBA observations of galaxies with metallicity measurements: a new method for determining the relation between submillimetre luminosity and dust mass
Using a new technique, we have determined a value for the constant ofproportionality between submillimetre emission and dust mass, the dustmass-absorption coefficient (κd) at 850μm. Ourmethod has an advantage over previous methods in that we avoidassumptions about the properties of dust in the interstellar medium. Ouronly assumption is that the fraction of metals incorporated in the dust(ɛ) in galaxies is a universal constant. To implement ourmethod, we require objects that have submillimetre and far-infrared fluxmeasurements as well as gas mass and metallicity estimates. We presentdata for all the galaxies with suitable measurements, including newsubmillimetre maps for five galaxies. We find κ850=0.07 +/- 0.02 m2 kg-1. We have also been able touse our sample to investigate our assumption that ɛ is auniversal constant. We find no evidence that ɛ is different fordwarf and giant galaxies, and show that the scatter in ɛ fromgalaxy to galaxy is apparently quite small.
| The distribution of atomic gas and dust in nearby galaxies - I. Presentation of matched-resolution VLA H I and SCUBA 850-μm maps
We present matched-resolution VLA HI and SCUBA 850-μm maps of 20IRAS-bright galaxies. Of the galaxies observed, two were not detected inHI and two were detected in absorption. The HI distributions of thegalaxies have a range of morphologies. Some of the systems appear HIdeficient in the central regions which could be due to a high conversionrate of HI into molecules or HI absorption. In contrast to the HI, the850-μm emission has a smooth distribution which is concentratedtowards the optical centre of each galaxy. We also find evidence for850-μm emission extending to the periphery of the optical disc insome of the galaxies. Finally, we note that the relative lack of850-μm emission when compared with HI does not necessarily mean thatthe atomic gas and dust do not have similar mass distributions.
| A New Database of Observed Spectral Energy Distributions of Nearby Starburst Galaxies from the Ultraviolet to the Far-Infrared
We present a database of UV-to-FIR data of 83 nearby starburst galaxies.The galaxies are selected based upon the availability of IUE data. Wehave recalibrated the IUE UV spectra for these galaxies by incorporatingthe most recent improvements. For 45 of these galaxies we useobservations by Storchi-Bergmann et al. and McQuade et al. for thespectra in the optical range. The NIR data are from new observationsobtained at the NASA/IRTF and the Mount Laguna Observatory, combinedwith the published results from observations at the Kitt Peak NationalObservatory. In addition, published calibrated ISO data are included toprovide mid-IR flux densities for some of the galaxies. Theoptical-to-IR data are matched as closely as possible to the IUE largeaperture. In conjunction with IRAS and ISO FIR flux densities, all thesedata form a set of observed spectral energy distributions (SEDs) of thenuclear regions of nearby starburst galaxies. The SEDs should be usefulin studying star formation and dust/gas attenuation in galaxies. We alsopresent the magnitudes in the standard BVRI and various HST/WFPC2bandpasses synthesized from the UV and optical wavelength ranges ofthese SEDs. For some of the galaxies, the HST/WFPC2 magnitudessynthesized from the SEDs are checked with those directly measured fromWFPC2 images to test the photometric errors of the optical data andtheir effective matching of apertures with the UV data. The implicationsof the new SEDs on the star formation rates and dust/gas attenuation arebriefly discussed.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| 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.
| The Westerbork HI survey of spiral and irregular galaxies. II. R-band surface photometry of late-type dwarf galaxies
R-band surface photometry is presented for 171 late-type dwarf andirregular galaxies. For a subsample of 46 galaxies B-band photometry ispresented as well. We present surface brightness profiles as well asisophotal and photometric parameters including magnitudes, diameters andcentral surface brightnesses. Absolute photometry is accurate to 0.1 magor better for 77% of the sample. For over 85% of the galaxies the radialsurface brightness profiles are consistent with published data withinthe measured photometric uncertainty. For most of the galaxies in thesample H I data have been obtained with the Westerbork Synthesis RadioTelescope. The galaxies in our sample are part of the WHISP project(Westerbork H I Survey of Spiral and Irregular Galaxies), which aims atmapping about 500 nearby spiral and irregular galaxies in H I. Theavailability of H I data makes this data set useful for a wide range ofstudies of the structure, dark matter content and kinematics oflate-type dwarf galaxies. Based on observations made with INT operatedon the island of La Palma by the Isaac Newton Group in the SpanishObservatorio del Roque de los Muchachos of the Instituto de Astrofisicade Canarias. The tables in Appendix A are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/390/863. Thefigures in Appendix B are only available in electronic formhttp://www.edpsciences.org
| The Westerbork HI survey of spiral and irregular galaxies. I. HI imaging of late-type dwarf galaxies
Neutral hydrogen observations with the Westerbork Synthesis RadioTelescope are presented for a sample of 73 late-type dwarf galaxies.These observations are part of the WHISP project (Westerbork H I Surveyof Spiral and Irregular Galaxies). Here we present H I maps, velocityfields, global profiles and radial surface density profiles of H I, aswell as H I masses, H I radii and line widths. For the late-typegalaxies in our sample, we find that the ratio of H I extent to opticaldiameter, defined as 6.4 disk scale lengths, is on average 1.8 +/- 0.8,similar to that seen in spiral galaxies. Most of the dwarf galaxies inthis sample are rich in H I, with a typical Mion {Hi}/L_B of1.5. The relative H I content M_ion {HI}/L_R increases towards fainterabsolute magnitudes and towards fainter surface brightnesses. Dwarfgalaxies with lower average H I column densities also have lower averageoptical surface brightnesses. We find that lopsidedness is as commonamong dwarf galaxies as it is in spiral galaxies. About half of thedwarf galaxies in our sample have asymmetric global profiles, a thirdhas a lopsided H I distribution, and about half shows signs of kinematiclopsidedness.
| Supernovae in isolated galaxies, in pairs and in groups of galaxies
In order to investigate the influence of environment on supernova (SN)production, we have performed a statistical investigation of the SNediscovered in isolated galaxies, in pairs and in groups of galaxies. 22SNe in 18 isolated galaxies, 48 SNe in 40 galaxy members of 37 pairs and211 SNe in 170 galaxy members of 116 groups have been selected andstudied. We found that the radial distributions of core-collapse SNe ingalaxies located in different environments are similar, and consistentwith those reported by Bartunov, Makarova & Tsvetkov. SNe discoveredin pairs do not favour a particular direction with respect to thecompanion galaxy. Also, the azimuthal distributions inside the hostmembers of galaxy groups are consistent with being isotropics. The factthat SNe are more frequent in the brighter components of the pairs andgroups is expected from the dependence of the SN rates on the galaxyluminosity. There is an indication that the SN rate is higher in galaxypairs compared with that in groups. This can be related to the enhancedstar formation rate in strongly interacting systems. It is concludedthat, with the possible exception of strongly interacting systems, theparent galaxy environment has no direct influence on SN production.
| The Tully-Fisher Relation as a Measure of Luminosity Evolution: A Low-Redshift Baseline for Evolving Galaxies
We use optical rotation curves to investigate the R-band Tully-Fisherproperties of a sample of 90 spiral galaxies in close pairs, covering arange of luminosities, morphological types, and degrees of tidaldistortion. The galaxies follow the Tully-Fisher relation remarkablywell, with the exception of eight distinct ~3 σ outliers. Althoughmost of the outliers show signs of recent star formation, gasdynamicaleffects are probably the dominant cause of their anomalous Tully-Fisherproperties. Four outliers with small emission-line widths have verycentrally concentrated line emission and truncated rotation curves; thecentral emission indicates recent gas infall after a close galaxy-galaxypass. These four galaxies may be local counterparts to compact, bluegalaxies at intermediate redshift. The remaining galaxies have anegligible offset from the reference Tully-Fisher relation, but ashallower slope (2.6 σ significance) and a 25% larger scatter. Weargue that triggered star formation is a significant contributor to theslope difference. We characterize the nonoutlier sample with measures ofdistortion and star formation to search for third-parameter dependencein the residuals of the TF relation. Severe kinematic distortion is theonly significant predictor of TF residuals; this distortion is not,however, responsible for the slope difference from the referencedistribution. Because the outliers are easily removed by sigma clipping,we conclude that even in the presence of some tidal distortion,detection of moderate (>~0.5 mag in rest-frame R) luminosityevolution should be possible with high-redshift samples the size of this90-galaxy study. The slope of the TF relation, although difficult tomeasure, is as fundamental for quantifying luminosity evolution as thezero-point offset. Some observations reported in this paper wereobtained at the Multiple Mirror Telescope Observatory, a facilityoperated jointly by the University of Arizona and the SmithsonianInstitution.
| Supernova 2000ez in NGC 3995
IAUC 7535 available at Central Bureau for Astronomical Telegrams.
| Supernova 2000ez in NGC 3995
IAUC 7533 available at Central Bureau for Astronomical Telegrams.
| The SCUBA Local Universe Galaxy Survey - I. First measurements of the submillimetre luminosity and dust mass functions
This is the first of a series of papers presenting results from theSCUBA Local Universe Galaxy Survey (SLUGS), the first statistical surveyof the submillimetre properties of the local Universe. As the initialpart of this survey, we have used the SCUBA camera on the James ClerkMaxwell Telescope to observe 104 galaxies from the IRAS Bright GalaxySample. We present here the 850-μm flux measurements. The 60-, 100-,and 850-μm flux densities are well fitted by single-temperature dustspectral energy distributions, with the sample mean and standarddeviation for the best-fitting temperature beingTd=35.6+/-4.9K and for the dust emissivity indexβ=1.3+/-0.2. The dust temperature was found to correlate with60-μm luminosity. The low value of β may simply mean that thesegalaxies contain a significant amount of dust that is colder than thesetemperatures. We have estimated dust masses from the 850-μm fluxesand from the fitted temperature, although if a colder component ataround 20K is present (assuming a β of 2), then the estimated dustmasses are a factor of 1.5-3 too low. We have made the first directmeasurements of the submillimetre luminosity function (LF) and of thedust mass function. Unlike the IRAS 60-μm LF, these are well fittedby Schechter functions. The slope of the 850-μm LF at lowluminosities is steeper than -2, implying that the LF must flatten atluminosities lower than we probe here. We show that extrapolating the60-μm LF to 850μm using a single temperature and β does notreproduce the measured submillimetre LF. A population of `cold' galaxies(Td<25K) emitting strongly at submillimetre wavelengthswould have been excluded from the 60-μm-selected sample. If suchgalaxies do exist, then this estimate of the 850-μm flux is biased(it is underestimated). Whether such a population does exist is unknownat present. We correlate many of the global galaxy properties with theFIR/submillimetre properties. We find that there is a tendency for lessluminous galaxies to contain hotter dust and to have a greater starformation efficiency (cf. Young). The average gas-to-dust ratio for thesample is 581+/-43 (using both the atomic and molecular hydrogen), whichis significantly higher than the Galactic value of 160. We believe thatthis discrepancy is probably due to a `cold dust' component atTd<=20K in our galaxies. There is a surprisingly tightcorrelation between dust mass and the mass of molecular hydrogen,estimated from CO measurements, with an intrinsic scatter of ~=50percent.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Panchromatic Study of Nearby Ultraviolet-bright Starburst Galaxies: Implications for Massive Star Formation and High-Redshift Galaxies
We present a panchromatic study of nearby starburst galaxies from theultraviolet to the visible, including narrowband Hα usingWisconsin-Indiana-Yale-NOAO (WIYN) and Hubble Space Telescope data, todetermine how star formation processes affect the morphologies andintegrated fluxes of nearby starbursts. We find that the UV and Hαmorphologies of starbursts tend to differ, although not in a standard orpredictable manner. From our sample of six nearby starbursts, threesystems show good correlations between UV and Hα fluxes, but wefind differences in UV and Hα morphology among the other three.Occasionally we find systems with well-defined H II regions without thecorresponding brightness in the UV, and vice versa. We discuss thelikely mechanisms behind these differences, which include starburstages, dust absorption, stellar energy ejecta through supernovae andwinds, and leakage of UV photons from stellar clusters. We conclude thatthe large-scale morphological features in starbursts are primarily dueto both age and absorption from a ``picket-fence'' dust distribution. Wefurther demonstrate the similarity and differences between these nearbystarbursts and high-redshift star-forming galaxies. The overallmorphology of our sample of starbursts changes little between UV andvisible wavelengths. If high-redshift galaxies are similar to thesestarbursts, their morphologies should change little between rest-frameUV and optical. We also show that FIR and UV spectral energydistributions and slopes can be used to determine large-scalemorphological features for extreme starbursts, with the steepest FIRslopes correlating with the most disturbed galaxies.
| Young, Star Forming Regions in NGC 3994 and NGC 3995
NGC 3991, NGC 3994, and NGC 3995 comprise a small group of interactinggalaxies. Groundbased images indicate significantly distorted morphologyin NGC 3991 and NGC 3995, while NGC 3994 appears to be a normal,inclined spiral. Spectra of NGC 3991 and NGC 3995 have features typicalof strong HII regions. NGC 3994 is a LINER. All three galaxies havestrong ultraviolet emission and have been observed with IUE (Kinney, etal. 1993). As part of an investigation of star formation in interactinggalaxies, we have obtained ultraviolet and visible images of the centralregions of NGC 3994 and 3995 with the Space Telescope ImagingSpectrograph on HST. Imaging was obtained in two ultraviolet(FUV-MAMA+F25QTZ, NUV-MAMA+F25CN182) and one visible (CCD+F28X50LP)band. Individual star forming knots (at HST resolution) have beenidentified in both galaxies. In NGC 3994 star-forming knots are foundtracing the spiral arms. Results from ground based spectroscopy indicatenuclear reddening of E(B-V) ~ 0.3- 0.4, suggesting that the lack ofUV-bright knots in the center is real and not due to extinction. Theknots in NGC 3995 have a distorted, 'hook shaped' distribution. Theknots are typically 12 - 45 pc in diameter (FWHM), with observed FUVfluxes of approximately 10-17 to 10-16 ergscm-2sec-1 Å-1. We compare ourimaging and spectroscopy data to current starburst models to constrainknot ages and masses. Knot characteristics as a function of location inthe galaxy will also be discussed. This work has been supported in partby NASA, under contract NAS5-31231, and through the Nevada Space GrantConsortium.
| 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.
| Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
| The 3-D structure of the Coma-A 1367 supercluster: Optical spectroscopy of 102 galaxies
Optical spectroscopy of 117 CGCG galaxies, 102 of which are projected inthe direction of the Coma-A 1367 supercluster, is reported. These newmeasurements, added to those found in the literature, bring to 1068 thenumber of CGCG galaxies in this region with available redshift, out of atotal of 1085 objects with m_p<= 15.7. We use these data to infer the3-D structure of the Coma supercluster. Based on observations obtainedwith the Loiano telescope belonging to the University of Bologna, Italy,and with the G. Haro telescope of the INAOE, Mexico.
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