WIKISKY.ORG
 Home Getting Started To Survive in the Universe News@Sky Astro Photo The Collection Forum Blog New! FAQ Press Login

# NGC 4383

Contents

### Images

DSS Images   Other Images

### Related articles

 The SAURON project - VII. Integral-field absorption and emission-line kinematics of 24 spiral galaxy bulgesWe present observations of the stellar and gas kinematics for arepresentative sample of 24 Sa galaxies obtained with our custom-builtintegral-field spectrograph SAURON operating on the William HerschelTelescope. The data have been homogeneously reduced and analysed bymeans of a dedicated pipeline. All resulting data cubes were spatiallybinned to a minimum mean signal-to-noise ratio of 60 per spatial andspectral resolution element. Our maps typically cover thebulge-dominated region. We find a significant fraction of kinematicallydecoupled components (12/24), many of them displaying central velocitydispersion minima. They are mostly aligned and co-rotating with the mainbody of the galaxies, and are usually associated with dust discs andrings detected in unsharp-masked images. Almost all the galaxies in thesample (22/24) contain significant amounts of ionized gas which, ingeneral, is accompanied by the presence of dust. The kinematics of theionized gas are consistent with circular rotation in a disc co-rotatingwith respect to the stars. The distribution of mean misalignmentsbetween the stellar and gaseous angular momenta in the sample suggeststhat the gas has an internal origin. The [OIII]/Hβ ratio is usuallyvery low, indicative of current star formation, and shows variousmorphologies (ring-like structures, alignments with dust lanes oramorphous shapes). The star formation rates (SFRs) in the sample arecomparable with that of normal disc galaxies. Low gas velocitydispersion values appear to be linked to regions of intense starformation activity. We interpret this result as stars being formed fromdynamically cold gas in those regions. In the case of NGC5953, the datasuggest that we are witnessing the formation of a kinematicallydecoupled component from cold gas being acquired during the ongoinginteraction with NGC5954. A Comparison of Hα and Stellar Scale Lengths in Virgo and Field SpiralsThe scale lengths of the old stars and ionized gas distributions arecompared for similar samples of Virgo Cluster members and field spiralgalaxies via Hα and broad R-band surface photometry. While theR-band and Hα scale lengths are, on average, comparable for thecombined sample, we find significant differences between the field andcluster samples. While the Hα scale lengths of the field galaxiesare a factor of 1.14+/-0.07 longer, on average, than their R-band scalelengths, the Hα scale lengths of Virgo Cluster members are, onaverage, 20% smaller than their R-band scale lengths. Furthermore, inVirgo, the scale length ratios are correlated with the size of thestar-forming disk: galaxies with smaller overall Hα extents alsoshow steeper radial falloff of star formation activity. At the sametime, we find no strong trends in scale length ratio as a function ofother galaxy properties, including galaxy luminosity, inclination,morphological type, central R-band light concentration, or bar type. Ourresults for Hα emission are similar to other results for dustemission, suggesting that Hα and dust have similar distributions.The environmental dependence of the Hα scale length placesadditional constraints on the evolutionary process(es) that cause gasdepletion and a suppression of the star formation rate in clusters ofgalaxies. A multibeam HI survey of the Virgo cluster - two isolated HI clouds?We have carried out a fully sampled large area (4°× 8°)21-cm HI line survey of part of the Virgo cluster using the Jodrell Bankmultibeam instrument. The survey has a sensitivity some three timesbetter than the standard HIJASS (HI Jodrell All Sky Survey) and HIPASS(HI Parkes All Sky Survey) surveys. We detect 31 galaxies, 27 of whichare well-known cluster members. The four new detections have beenconfirmed in the HIPASS data and by follow-up Jodrell Bank pointedobservations. One object lies behind M86, but the other three have noobvious optical counterparts upon inspection of the digital sky surveyfields. These three objects were mapped at Arecibo with a smaller3.6-arcmin half power beam width (HPBW) and a four times bettersensitivity than the Jodrell Bank data, which allow an improveddetermination of the dimensions and location of two of the objects, butsurprisingly failed to detect the third. The two objects are resolved bythe Arecibo beam, giving them a size far larger than any optical imagesin the nearby field. To our mass limit of 5 ×107(Δv/50 km s-1) Msolar andcolumn density limit of 3 × 1018(Δv/50 kms-1) atom cm-2, these new detections representonly about 2 per cent of the cluster atomic hydrogen mass. Ourobservations indicate that the HI mass function of the cluster turnsdown at the low-mass end, making it very different to the field galaxyHI mass function. This is quite different to the Virgo cluster opticalluminosity function, which is much steeper than that in the generalfield. Many of the sample galaxies are relatively gas-poor compared withHI selected samples of field galaxies, confirming the anaemic spirals'view of Virgo cluster late-type galaxies. The velocity distribution ofthe HI detected galaxies is also very different to that of the clusteras a whole. There are relatively more high-velocity galaxies in the HIsample, suggesting that they form part of a currently infallingpopulation. The HI sample with optical identifications has a minimum HIcolumn density cut-off more than an order of magnitude above thatexpected from the sensitivity of the survey. This observed columndensity is above the normally expected level for star formation tooccur. The two detections with no optical counterparts have very muchlower column densities than that of the rest of the sample, below thestar formation threshold. Hα Morphologies and Environmental Effects in Virgo Cluster Spiral GalaxiesWe describe the various Hα morphologies of Virgo Cluster andisolated spiral galaxies and associate the Hα morphologies withthe types of environmental interactions that have altered the clustergalaxies. The spatial distributions of Hα and R-band emission areused to divide the star formation morphologies of the 52 Virgo Clusterspiral galaxies into several categories: normal (37%), anemic (6%),enhanced (6%), and (spatially) truncated (52%). Truncated galaxies arefurther subdivided on the basis of their inner star formation rates intotruncated/normal (37%), truncated/compact (6%), truncated/anemic (8%),and truncated/enhanced (2%). The fraction of anemic galaxies isrelatively small (6%-13%) in both environments, suggesting thatstarvation is not a major factor in the reduced star formation rates ofVirgo spiral galaxies. The majority of Virgo spiral galaxies have theirHα disks truncated (52%), whereas truncated Hα disks arerarer in isolated galaxies (12%). Most of the Hα-truncatedgalaxies have relatively undisturbed stellar disks and normal toslightly enhanced inner disk star formation rates, suggesting thatintracluster medium-interstellar medium (ICM-ISM) stripping is the mainmechanism causing the reduced star formation rates of Virgo spiralgalaxies. Several of the truncated galaxies are peculiar, with enhancedcentral star formation rates, disturbed stellar disks, and barlikedistributions of luminous H II complexes inside the central 1 kpc but nostar formation beyond, suggesting that recent tidal interactions orminor mergers have also influenced their morphology. Two highly inclinedHα-truncated spiral galaxies have numerous extraplanar H IIregions and are likely in an active phase of ICM-ISM stripping. Severalspiral galaxies have one-sided Hα enhancements at the outer edgeof their truncated Hα disks, suggesting modest local enhancementsin their star formation rates due to ICM-ISM interactions. Low-velocitytidal interactions and perhaps outer cluster H I accretion seem to bethe triggers for enhanced global star formation in four Virgo galaxies.These results indicate that most Virgo spiral galaxies experienceICM-ISM stripping, many experience significant tidal effects, and manyexperience both. Massive Star Formation Rates and Radial Distributions from Hα Imaging of 84 Virgo Cluster and Isolated Spiral GalaxiesThe massive star formation properties of 55 Virgo Cluster and 29isolated S0-Scd bright (MB<=-18) spiral galaxies arecompared via analyses of R and Hα surface photometry andintegrated fluxes as functions of Hubble type and central R lightconcentration (bulge-to-disk ratio). In the median, the total normalizedmassive star formation rates (NMSFRs) in Virgo Cluster spiral galaxiesare reduced by factors of up to 2.5 compared with isolated spiralgalaxies of the same type or concentration, with a range from enhanced(up to 2.5 times) to strongly reduced (up to 10 times). Within the inner30% of the optical disk, Virgo Cluster and isolated spiral galaxies havesimilar ranges in NMSFRs, with similar to enhanced (up to 4 times)median NMSFRs for Virgo galaxies. NMSFRs in the outer 70% of the opticaldisk are reduced in the median by factors of up to 9 for Virgo Clusterspiral galaxies, with more severely reduced star formation atprogressively larger disk radii. Thus, the reduction in total starformation of Virgo Cluster spiral galaxies is caused primarily byspatial truncation of the star-forming disks. The correlation between HI deficiency and R light central concentration is much weaker than thecorrelation between H I deficiency and Hubble type. The previouslyobserved systematic difference in H I spatial distributions andkinematics between early- and late-type spiral galaxies in the VirgoCluster is at least partially due to the misleading classification ofstripped spiral galaxies as early types. Intraclustermedium-interstellar medium stripping of the gas from spiral galaxies islikely responsible for the truncated star-forming disks of Virgo Clusterspiral galaxies. This effect may be responsible for a significant partof the morphology-density relationship, in that a large fraction ofVirgo Cluster galaxies classified as Sa galaxies are H I-deficientgalaxies with truncated star-forming disks rather than galaxies withlarge bulge-to-disk ratios. Radio and Far-Infrared Emission as Tracers of Star Formation and Active Galactic Nuclei in Nearby Cluster GalaxiesWe have studied the radio and far-infrared (FIR) emission from 114galaxies in the seven nearest clusters (<100 Mpc) with prominentX-ray emission to investigate the impact of the cluster environment onthe star formation and active galactic nucleus (AGN) activity in themember galaxies. The X-ray selection criterion is adopted to focus onthe most massive and dynamically relaxed clusters. A large majority ofcluster galaxies show an excess in radio emission over that predictedfrom the radio-FIR correlation, the fraction of sources with radioexcess increases toward cluster cores, and the radial gradient in theFIR/radio flux ratio is a result of radio enhancement. Of theradio-excess sources, 70% are early-type galaxies, and the same fractionhost an AGN. The galaxy density drops by a factor of 10 from thecomposite cluster center out to 1.5 Mpc, yet galaxies show no change inFIR properties over this region and show no indication of masssegregation. We have examined in detail the physical mechanisms thatmight impact the FIR and radio emission of cluster galaxies. Whilecollisional heating of dust may be important for galaxies in clustercenters, it appears to have a negligible effect on the observed FIRemission for our sample galaxies. The correlations between radio and FIRluminosity and radius could be explained by magnetic compression fromthermal intracluster medium pressure. We also find that simple delayedharassment cannot fully account for the observed radio, FIR, and mid-IRproperties of cluster galaxies. The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39 Tracing the star formation history of cluster galaxies using the Hα/UV flux ratioSince the Hα and UV fluxes from galaxies are sensitive to stellarpopulations of ages <107 and ≈ 108 yrrespectively, their ratio f(Hα)/f(UV) provides us with a tool tostudy the recent t ≤ 108 yr star formation history ofgalaxies, an exercise that we present here applied to 98 galaxies in 4nearby clusters (Virgo, Coma, Abell 1367 and Cancer). The observedf(Hα)/f(UV) ratio is  a factor of two smaller than theexpected one as determined from population synthesis models assuming arealistic delayed, exponentially declining star formation history. Wediscuss various mechanisms that may have affected the observedf(Hα)/f(UV) ratio and we propose that the above discrepancy arisesfrom either the absorption of Lyman continuum photons by dust within thestar formation regions or from the occurrence of star formationepisodes. After splitting our sample into different subsamples accordingto evolutionary criteria we find that our reference sample of galaxiesunaffected by the cluster environment show an average value off(Hα)/f(UV) two times lower than the expected one. We argue thatthis difference must be mostly due to absorption of ≈45% of the Lymancontinuum photons within star forming regions. Galaxies with clear signsof an ongoing interaction show average values of f(Hα)/f(UV)slightly higher than the reference value, as expected if those objectshad SFR increased by a factor of ≃4. The accuracy of the currentUV and Hα photometry is not yet sufficient to clearly disentanglethe effect of interactions on the f(Hα)/f(UV) ratio, butsignificant observational improvements are shortly expected to resultfrom the GALEX mission.Tables 1-3 are only available in electronic form athttp://www.edpsciences.org Radio continuum spectra of galaxies in the Virgo cluster regionNew radio continuum observations of galaxies in the Virgo cluster regionat 4.85, 8.6, and 10.55 GHz are presented. These observations arecombined with existing measurements at 1.4 and 0.325 GHz. The sampleincludes 81 galaxies where spectra with more than two frequencies couldbe derived. Galaxies that show a radio-FIR excess exhibit centralactivity (HII, LINER, AGN). The four Virgo galaxies with the highestabsolute radio excess are found within 2° of the centerof the cluster. Galaxies showing flat radio spectra also host activecenters. There is no clear trend between the spectral index and thegalaxy's distance to the cluster center.Figure 3 is only available in electronic form athttp://www.edpsciences.orgTable 3 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/1 Spectrophotometry of galaxies in the Virgo cluster. II. The dataDrift-scan mode (3600-6800 Å) spectra with 500 Starbursts in barred spiral galaxies. VI. HI observations and the K-band Tully-Fisher relationThis paper reports a study of the effect of a bar on the neutralhydrogen (HI) content of starburst and Seyfert galaxies. We also makecomparisons with a sample of normal'' galaxies and investigate howwell starburst and Seyfert galaxies follow the fundamental scalingTully-Fisher (TF) relation defined for normal galaxies. 111 Markarian(Mrk) IRAS galaxies were observed with the Nançay radiotelescope,and HI data were obtained for 80 galaxies, of which 64 are newdetections. We determined the (20 and 50%) linewidths, the maximumvelocity of rotation and total HI flux for each galaxy. Thesemeasurements are complemented by data from the literature to form asample of Mrk IRAS (74% starburst, 23% Seyfert and 3% unknown) galaxiescontaining 105 unbarred and 113 barred ones. Barred galaxies have lowertotal and bias-corrected HI masses than unbarred galaxies, and this istrue for both Mrk IRAS and normal galaxies. This robust result suggeststhat bars funnel the HI gas toward the center of the galaxy where itbecomes molecular before forming new stars. The Mrk IRAS galaxies havehigher bias-corrected HI masses than normal galaxies. They also showsignificant departures from the TF relation, both in the B and K bands.The most deviant points from the TF relation tend to have a strongfar-infrared luminosity and a low oxygen abundance. These resultssuggest that a fraction of our Mrk IRAS galaxies are still in theprocess of formation, and that their neutral HI gas, partly of externalorigin, has not yet reached a stationary state.Based on observations obtained at the large radiotelescope ofObservatoire de Nançay, operated by Observatoire de Paris.Tables 5 and 6 are only (and Table 4 also) available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/515 Minor-axis velocity gradients in disk galaxiesWe present the ionized-gas kinematics and photometry of a sample of 4spiral galaxies which are characterized by a zero-velocity plateau alongthe major axis and a velocity gradient along the minor axis,respectively. By combining these new kinematical data with thoseavailable in the literature for the ionized-gas component of the S0s andspirals listed in the Revised Shapley-Ames Catalog of Bright Galaxies werealized that about 50% of unbarred galaxies show a remarkable gasvelocity gradient along the optical minor axis. This fraction rises toabout 60% if we include unbarred galaxies with an irregular velocityprofile along the minor axis. This phenomenon is observed all along theHubble sequence of disk galaxies, and it is particularly frequent inearly-type spirals. Since minor-axis velocity gradients are unexpectedif the gas is moving onto circular orbits in a disk coplanar to thestellar one, we conclude that non-circular and off-plane gas motions arenot rare in the inner regions of disk galaxies.Based on observations carried out at the European Southern Observatoryin La Silla (Chile) (ESO 69.B-0706 and 70.B-0338), with the MultipleMirror Telescope which is a joint facility of the SmithsonianInstitution and the University of Arizona, and with the ItalianTelescopio Nazionale Galileo (AOT-5, 3-18) at the Observatorio del Roquede los Muchachos in La Palma (Spain).Table 1 is only available in electronic form athttp://www.edpsciences.org. Table 5 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/507 Radio emission from AGN detected by the VLA FIRST surveyUsing 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 Dust emission in the far-infrared as a star formation tracer at z= 0: systematic trends with luminosityWe investigate whether dust emission in the far-infrared (far-IR)continuum provides a robust estimate of the star formation rate (SFR)for a nearby, normal late-type galaxy. We focus on the ratio of the40-1000 μm luminosity (Ldust) to the far-ultraviolet(far-UV) (0.165 μm) luminosity, which is connected to recent episodesof star formation. Available total photometry at 0.165, 60, 100 and 170μm limits the statistics to 30 galaxies, which, however, span a largerange in observed (and, thus, attenuated by dust) K-band (2.2 μm)luminosity, morphology and inclination (i). This sample shows that theratio of Ldust to the observed far-UV luminosity depends notonly on i, as expected, but also on morphology and, in a tighter way, onobserved K-band luminosity. We find thatLdust/LFUV~ e-τK (α+0.62)LK0.62, where LFUV andLK are the unattenuated stellar luminosities in far-UV and K,respectively, and α is the ratio of the attenuation optical depthsat 0.165 μm (τFUV) and 2.2 μm (τK).This relation is to zeroth order independent of i and morphology. It maybe further expressed asLdust/LFUV~LδK, whereδ= 0.61 - 0.02α, under the observationally motivatedassumption that, for an average inclination,e-τK~L-0.02K. We adoptcalculations of two different models of attenuation of stellar light byinternal dust to derive solid-angle-averaged values of α. We findthat δ is positive and decreases towards 0 from the more luminousto the less luminous galaxies. This means that there is no universalratio of far-IR luminosity to unattenuated far-UV luminosity for nearby,normal late-type galaxies. The far-IR luminosity systematicallyoverestimates SFR in more luminous, earlier-type spirals, owing to theincreased fractional contribution to dust heating of optical/near-IRphotons in these objects. Conversely, it systematically underestimatesSFR in fainter, later-type galaxies, the τFUV of which isreduced. The limited statistics and the uncertainty affecting theprevious scaling relations do not allow us to establish quantitativeconclusions, but an analogous analysis making use of larger data sets,available in the near future (e.g. from GALEX, ASTRO-F and SIRTF), andof more advanced models will allow a quantitative test of ourconclusions. The PDS versus Markarian starburst galaxies: comparing strong and weak IRAS emitter at 12 and 25 μm in the nearby UniverseThe characteristics of the starburst galaxies from the Pico dos Diassurvey (PDS) are compared with those of the nearby ultraviolet (UV)bright Markarian starburst galaxies, having the same limit in redshift(vh < 7500 km s-1) and absolute B magnitude(MB < -18). An important difference is found: theMarkarian galaxies are generally undetected at 12 and 25 μm in IRAS.This is consistent with the UV excess shown by these galaxies andsuggests that the youngest star-forming regions dominating thesegalaxies are relatively free of dust.The far-infrared selection criteria for the PDS are shown to introduce astrong bias towards massive (luminous) and large size late-type spiralgalaxies. This is contrary to the Markarian galaxies, which are found tobe remarkably rich in smaller size early-type galaxies. These resultssuggest that only late-type spirals with a large and massive disc arestrong emitters at 12 and 25 μm in IRAS in the nearby Universe.The Markarian and PDS starburst galaxies are shown to share the sameenvironment. This rules out an explanation of the differences observedin terms of external parameters. These differences may be explained byassuming two different levels of evolution, the Markarian being lessevolved than the PDS galaxies. This interpretation is fully consistentwith the disc formation hypothesis proposed by Coziol et al. to explainthe special properties of the Markarian SBNG. The IRAS Revised Bright Galaxy SampleIRAS 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 thecharacteristic'' 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. Star formation rate in galaxies from UV, IR, and Hα estimatorsInfrared (IR) luminosity of galaxies originating from dust thermalemission can be used as an indicator of the star formation rate (SFR).Inoue et al. (\cite{inoue00}, IHK) have derived a formula for theconversion from dust IR luminosity to SFR by using the following threequantities: the fraction of Lyman continuum luminosity absorbed by gas(f), the fraction of UV luminosity absorbed by dust (epsilon ), and thefraction of dust heating from old (ga 108 yr) stellarpopulations (eta ). We develop a method to estimate those threequantities based on the idea that the various way of SFR estimates fromultraviolet (UV) luminosity (2000 Å luminosity), Hαluminosity, and dust IR luminosity should return the same SFR. Afterapplying our method to samples of galaxies, the following results areobtained in our framework. First, our method is applied to a sample ofstar-forming galaxies, finding that f ~ 0.6, epsilon ~ 0.5, and eta ~0.4 as representative values. Next, we apply the method to a starburstsample, which shows larger extinction than the star-forming galaxysample. With the aid of f, epsilon , and eta , we are able to estimatereliable SFRs from UV and/or IR luminosities. Moreover, the Hαluminosity, if the Hα extinction is corrected by using the Balmerdecrement, is suitable for a statistical analysis of SFR, because thesame {correction factor for the Lyman continuum extinction (i.e. 1/f)}is applicable to both normal and starburst galaxies over all the rangeof SFR. The metallicity dependence of f and epsilon is also tested:Only the latter proves to have a correlation with metallicity. As anextension of our result, the local (z=0) comoving density of SFR can beestimated with our dust extinction corrections. We show that all UV,Hα , and IR comoving luminosity densities at z=0 give a consistentSFR per comoving volume ( ~ 3x 10-2h M_sun yr-1Mpc-3). Useful formulae for SFR estimate are listed.Tables 1 and 2, and Appendix A are only available in electronic form athttp://www.edpsciences.org The far-infrared/radio correlation in the ISO era. The warm and cold far-infrared/radio correlationsWe present the correlation between the far-infrared (FIR) and radioemissions from a composite sample of 72 nearby normal galaxies observedwith the ISOPHOT instrument on board the Infrared Space Observatory. Thegalaxies in the sample have measurements at three FIR wavelengths (60,100 and 170 mu m), which allowed a direct determination of the warm andcold FIR emission components. This is the first time that thecorrelation has been established for the total FIR luminosity, of whichmost is carried by the cold dust component predominantly emittinglongwards of the spectral coverage of IRAS. The slope of thiscorrelation is slightly non-linear (1.10+/- 0.03). Separate correlationsbetween the warm and cold FIR emission components and the radio emissionhave also been derived. The slope of the warm FIR/radio correlation wasfound to be linear (1.03 +/- 0.03). For the cold FIR/radio correlationwe found a slightly non-linear (1.13 +/- 0.04) slope. We qualitativelyinterpret the correlations in terms of star formation rate and find thatboth the FIR and radio emissions may be consistent with a non-lineardependence on star formation rate for galaxies not undergoing starburstactivity.Based on observations with the Infrared Space Observatory (ISO), an ESAproject with instruments funded by ESA member States (especially the PIcountries: France, Germany, The Netherlands, and the UK) and with theparticipation of ISAS and NASA.Table \ref{Tab2} and Appendices A and B are only available in electronicform at http://www.edpsciences.org A new catalogue of ISM content of normal galaxiesWe have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of normality''. Thedefinition of a normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5 The cold gas properties of Markarian galaxiesA sample of 61 Markarian galaxies detected in the CO line was compiled.Using available HI, element H2, optical and radio continuumdata, the analysis of the gas kinematics and the star formationproperties for this sample of galaxies was performed. The mainconclusion can be summarized as follows: (1) The HI and CO line widthsare well correlated. Interaction between galaxies has no influence onthe CO line broadening. A rapidly rotating nuclear disk in the galaxymight lead to the CO line broadening with less influence on the HI line.(2) The atomic and molecular gas surface densities are well correlatedwith the blue, FIR and radio continuum surface brightness; however, thecorrelation for molecular component is stronger.\ (3) In general, thegalaxies with UV-excess (Markarian galaxies) do not differ in their starformation properties from the non-UV galaxies. The luminosity function of the Virgo Cluster from MB=-22 to -11We measure the galaxy luminosity function (LF) for the Virgo Clusterbetween blue magnitudes MB=-22 and -11 from wide-fieldcharge-coupled device (CCD) imaging data. The LF is only graduallyrising for -22 The SAURON project - II. Sample and early resultsEarly results are reported from the SAURON survey of the kinematics andstellar populations of a representative sample of nearby E, S0 and Sagalaxies. The survey is aimed at determining the intrinsic shape of thegalaxies, their orbital structure, the mass-to-light ratio as a functionof radius, the age and metallicity of the stellar populations, and thefrequency of kinematically decoupled cores and nuclear black holes. Theconstruction of the representative sample is described, and itsproperties are illustrated. A comparison with long-slit spectroscopicdata establishes that the SAURON measurements are comparable to, orbetter than, the highest-quality determinations. Comparisons arepresented for NGC 3384 and 4365, where stellar velocities and velocitydispersions are determined to a precision of 6kms-1, and theh3 and h4 parameters of the line-of-sight velocitydistribution to a precision of better than 0.02. Extraction of accurategas emission-line intensities, velocities and linewidths from the datacubes is illustrated for NGC 5813. Comparisons with published linestrengths for NGC 3384 and 5813 reveal uncertainties of <~0.1Åon the measurements of the Hβ, Mg b and Fe5270 indices.Integral-field mapping uniquely connects measurements of the kinematicsand stellar populations to the galaxy morphology. The maps presentedhere illustrate the rich stellar kinematics, gaseous kinematics, andline-strength distributions of early-type galaxies. The results includethe discovery of a thin, edge-on, disc in NGC 3623, confirm theaxisymmetric shape of the central region of M32, illustrate the LINERnucleus and surrounding counter-rotating star-forming ring in NGC 7742,and suggest a uniform stellar population in the decoupled core galaxyNGC 5813. Far-Infrared Census of Starburst-Seyfert ConnectionFar-infrared flux densities are newly extracted from the IRAS databasefor the Revised Shapley-Ames and CfA complete samples of Seyfertgalaxies. These data are used to classify the Seyfert galaxies intothose where the far-infrared continuum emission is dominated by theactive galactic nucleus (AGN), circumnuclear starburst, or host galaxy.While AGN-dominant objects consist of comparable numbers of Seyfert 1and 2 galaxies, starburst- and host-dominant objects consistpreferentially of Seyfert 2 galaxies. Thus, in addition to the dustytorus, the circumnuclear starburst region and host galaxy are importantin hiding the broad-line region. Morphologically, starburst-dominantSeyfert galaxies are of later types and more strongly interacting thanAGN-dominant Seyfert galaxies. In a later type galaxy, the AGN centralengine has a lower Eddington luminosity, and the gaseous content ishigher. The gas is efficiently supplied to the starburst via agalaxy-galaxy interaction. Morphologies of host-dominant Seyfertgalaxies are of various types. Since starbursts in Seyfert galaxies areolder than those in classical starburst galaxies, we propose anevolution from starburst to starburst-dominant Seyfert to host-dominantSeyfert for a late-type galaxy. An evolution from AGN-dominant Seyfertto host-dominant Seyfert is proposed for an early-type galaxy. Thesesequences have durations of a few times 108 yr and occurrepeatedly within a galaxy during its evolution from a late type to anearly type. The Three-dimensional Structure of the Virgo Cluster Region from Tully-Fisher and H I DataThe distances and H I contents of 161 spiral galaxies in the region ofthe Virgo cluster are used to gain insight into the complicatedstructure of this galaxy system. Special attention has been paid to theinvestigation of the suggestion presented in an earlier work that someperipheral Virgo groups may contain strongly gas-deficient spiralgalaxies. The three-dimensional galaxy distribution has been inferredfrom quality distance estimates obtained by averaging distance modulibased on the Tully-Fisher relationship taken from eight published datasets previously homogenized, resulting in a relation with a dispersionof 0.41 mag. Previous findings that the spiral distribution issubstantially more elongated along the line of sight than in the planeof the sky are confirmed by the current data. In addition, an importanteast-west disparity in this effect has been detected. The overallwidth-to-depth ratio of the Virgo cluster region is about 1:4, with themost distant objects concentrated in the western half. The filamentarystructure of the spiral population and its orientation are alsoreflected by the H I-deficient objects alone. The H I deficiency patternshows a central enhancement extending from ~16 to 22 Mpc inline-of-sight distance; most of this enhancement arises from galaxiesthat belong to the Virgo cluster proper. However, significant gasdeficiencies are also detected outside the main body of the cluster in aprobable group of galaxies at line-of-sight distances ~25-30 Mpc, lyingin the region dominated by the southern edge of the M49 subcluster andclouds W' and W, as well as in various foreground galaxies. In the Virgoregion, the H I content of the galaxies then is not a straightforwardindicator of cluster membership. Bar Galaxies and Their EnvironmentsThe 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 CatalogWe 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. Hα surface photometry of galaxies in the Virgo cluster. IV. The current star formation in nearby clusters of galaxiesHα +[NII] imaging observations of 369 late-type (spiral) galaxiesin the Virgo cluster and in the Coma/A1367 supercluster are analyzed,covering 3 rich nearby clusters (A1367, Coma and Virgo) and nearlyisolated galaxies in the Great-Wall. They constitute an opticallyselected sample (mp<16.0) observed with ~ 60 %completeness. These observations provide us with the current(T<107 yrs) star formation properties of galaxies that westudy as a function of the clustercentric projected distances (Theta ).The expected decrease of the star formation rate (SFR), as traced by theHα EW, with decreasing Theta is found only when galaxies brighterthan Mp ~ -19.5 are considered. Fainter objects show no orreverse trends. We also include in our analysis Near Infrared data,providing information on the old (T>109 yrs) stars. Puttogether, the young and the old stellar indicators give the ratio ofcurrently formed stars over the stars formed in the past, orbirthrate'' parameter b. For the considered galaxies we also determinethe global gas content'' combining HI with CO observations. We definethe gas deficiency'' parameter as the logarithmic difference betweenthe gas content of isolated galaxies of a given Hubble type and themeasured gas content. For the isolated objects we find that b decreaseswith increasing NIR luminosity. In other words less massive galaxies arecurrently forming stars at a higher rate than their giant counterpartswhich experienced most of their star formation activity at earliercosmological epochs. The gas-deficient objects, primarily members of theVirgo cluster, have a birthrate significantly lower than the isolatedobjects with normal gas content and of similar NIR luminosity. Thisindicates that the current star formation is regulated by the gaseouscontent of spirals. Whatever mechanism (most plausibly ram-pressurestripping) is responsible for the pattern of gas deficiency observed inspiral galaxies members of rich clusters, it also produces the observedquenching of the current star formation. A significant fraction of gas`healthy'' (i.e. with a gas deficiency parameter less than 0.4) andcurrently star forming galaxies is unexpectedly found projected near thecenter of the Virgo cluster. Their average Tully-Fisher distance isfound approximately one magnitude further away (muo = 31.77)than the distance of their gas-deficient counterparts (muo =30.85), suggesting that the gas healthy objects belong to a cloudprojected onto the cluster center, but in fact lying a few Mpc behindVirgo, thus unaffected by the dense IGM of the cluster. Based onobservations taken at the Observatorio Astronómico Nacional(Mexico), the OHP (France), Calar Alto and NOT (Spain) observatories.Table \ref{tab4} is only available in electronic form athttp://www.edpsciences.org Hα surface photometry of galaxies in the Virgo cluster. II. Observations with the OHP and Calar Alto 1.2 m telescopesWe present Hα line imaging observations of 122 galaxies obtainedwith the 1.20 m telescopes of the Observatoire de Haute Provence (OHP)and of Calar Alto. The observed galaxies are mostly Virgo clustermembers (95), along with 10 objects in the Coma/A1367 supercluster, 6 inthe clusters A2197 and A2199, and 11 nearby galaxies taken as fillers.Hα +[NII] fluxes and equivalent widths, as well as images of allthe detected targets, are presented. Based on observations taken at theObservatoire de Haute Provence (OHP) (France), operated by the FrenchCNRS, and Calar Alto Observatory (Spain), operated by theMax-Planck-Institut für Astronomie (Heidelberg) jointly with theSpanish National Commission for Astronomy. Figure 1 is only available inelectronic form at http://www.edpsciences.org Star formation and dust extinction in nearby star-forming and starburst galaxiesWe study the star formation rate and dust extinction properties of asample of nearby star-forming galaxies as derived from Hα and UV (~ 2000 Å) observations and we compare them to those of a sample ofstarburst galaxies. The dust extinction in Hα is estimated fromthe Balmer decrement and the extinction in UV using the FIR to UV fluxratio or the attenuation law for starburst galaxies of Calzetti et al.(\cite{calzetti5}). The Hα and UV emissions are stronglycorrelated with a very low scatter for the star-forming objects and witha much higher scatter for the starburst galaxies. The Hα to UVflux ratio is found to be larger by a factor ~ 2 for the starburstgalaxies. We compare both samples with a purely UV selected sample ofgalaxies and we conclude that the mean Hα and UV properties ofnearby star-forming galaxies are more representative of UV-selectedgalaxies than starburst galaxies. We emphasize that the Hα to UVflux ratio is strongly dependent on the dust extinction: the positivecorrelation found between FHα/FUV andFFIR/FUV vanishes when the Hα and UV fluxare corrected for dust extinction. The Hα to UV flux ratiosconverted into star formation rate and combined with the Balmerdecrement measurements are tentatively used to estimate the dustextinction in UV. An Atlas of Hα and R Images and Radial Profiles of 63 Bright Virgo Cluster Spiral GalaxiesNarrowband Hα and broadband R images and radial profiles arepresented for 63 bright spiral galaxies in the Virgo Cluster. The sampleis complete for Sb-Scd galaxies with B0T<=12and inclination <=75°. Isophotal radii, disk scale lengths,concentration parameters, and integrated fluxes are derived for thesample galaxies.
Submit a new article