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|Hα Imaging of Early-Type Sa-Sab Spiral Galaxies. II. Global Properties|
New results, based on one of the most comprehensive Hα imagingsurveys of nearby Sa-Sab spirals completed to date, reveals early-typespirals to be a diverse group of galaxies that span a wide range inmassive star formation rates. While the majority of Sa-Sab galaxies inour sample are forming stars at a modest rate, a significant fraction(~29%) exhibit star formation rates greater than 1 Msolaryr-1, rivaling the most prolifically star-forming late-typespirals. A similar diversity is apparent in the star formation historyof Sa-Sab spirals as measured by their Hα equivalent widths.Consistent with our preliminary results presented in the first paper inthis series, we find giant H II regions [L(Hα)>=1039ergs s-1] in the disks of ~37% of early-type spirals. Wesuspect that recent minor mergers or past interactions are responsiblefor the elevated levels of Hα emission and, perhaps, for thepresence of giant H II regions in these galaxies. Our results, however,are not in total agreement with the Hα study of Kennicutt &Kent, who did not find any early-type spirals with Hα equivalentwidths >14 Å. A close examination of the morphologicalclassification of galaxies, however, suggests that systematicdifferences between the Revised Shapley-Ames Catalog and the SecondReference Catalogue may be responsible for the contrasting results.Based on observations obtained with the 3.5 m telescope at Apache PointObservatory (APO) and the 0.9 m telescope at Kitt Peak NationalObservatory (KPNO). The APO 3.5 m telescope is owned and operated by theAstrophysical Research Consortium.
|Principal component analysis of International Ultraviolet Explorer galaxy spectra|
We analyse the UV spectral energy distribution of a sample of normalgalaxies listed in the International Ultraviolet Explorer (IUE) NewlyExtracted Spectra (INES) Guide No. 2 - Normal Galaxies using a principalcomponent analysis. The sample consists of the IUE short-wavelength (SW)spectra of the central regions of 118 galaxies, where the IUE apertureincluded more than 1 per cent of the galaxy size. The principalcomponents are associated with the main components observed in theultraviolet (UV) spectra of galaxies. The first component, accountingfor the largest source of diversity, may be associated with the UVcontinuum emission. The second component represents the UV contributionof an underlying evolved stellar population. The third component issensitive to the amount of activity in the central regions of galaxiesand measures the strength of star-formation events.In all the samples analysed here, the principal component representativeof star-forming activity accounts for a significant percentage of thevariance. The fractional contribution to the spectral energydistribution (SED) by the evolved stars and by the young population aresimilar.Projecting the SEDs on to their eigenspectra, we find that none of thecoefficients of the principal components can outline an internalcorrelation or can correlate with the optical morphological types. In asubsample of 43 galaxies, consisting of almost only compact and BCDgalaxies, the third principal component defines a sequence related tothe degree of starburst activity of the galaxy.
|Starbursts in barred spiral galaxies. VI. HI observations and the K-band Tully-Fisher relation|
This 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 (188.8.131.52) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/515
|Chemically consistent evolution of galaxies. II. Spectrophotometric evolution from zero to high redshift|
The composite stellar populations of galaxies comprise stars of a widerange of metallicities. Subsolar metallicities become increasinglyimportant, both in the local universe when going from early towardslater galaxy types as well as for dwarf galaxies and for all types ofgalaxies towards higher redshifts.We present a new generation of chemically consistent evolutionarysynthesis models for galaxies of various spectral types from E throughSd. The models follow the chemical enrichment of the ISM and take intoaccount the increasing initial metallicity of successive stellargenerations using recently published metallicity dependent stellarevolutionary isochrones, spectra and yields.Our first set of closed-box 1-zone models does not include any spatialresolution or dynamics. For a Salpeter initial mass function (IMF) thestar formation rate (SFR) and its time evolution are shown tosuccessfully parameterise spectral galaxy types E, ..., Sd. We show howthe stellar metallicity distribution in various galaxy types build upwith time to yield after 12 Gyr agreement with stellar metallicitydistributions observed in our and other local galaxies.The models give integrated galaxy spectra over a wide wavelength range(90.9 Å-160 μm), which for ages of 12 Gyr are in goodagreement not only with observed broad band colours but also withtemplate spectra for the respective galaxy types.Using filter functions for Johnson-Cousins U, B, V, RC,IC, as well as for HST broad band filters in the optical andBessel & Brett's NIR J, H, K filter system, we calculate theluminosity and colour evolution of model galaxies over a Hubble time.Including a standard cosmological model (H0 = 65,Ω0 = 0.1) and the attenuation by intergalactic hydrogenwe present evolutionary and cosmological corrections as well as apparentluminosities in various filters over the redshift range from z 5to the present for our galaxy types and compare to earlier models usingsingle (=solar) metallicity input physics only. We also resent a firstcomparison of our cc models to HDF data. A more detailed comparison withHubble Deep Field (HDF) and other deep field data and an analysis andinterpretation of high redshift galaxies in terms of ages,metallicities, star formation histories and, galaxy types will be thesubject of a forthcoming paper.
|The PDS versus Markarian starburst galaxies: comparing strong and weak IRAS emitter at 12 and 25 μm in the nearby Universe|
The 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 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 Role of Interactions in the Evolution of Highly Star-forming Early-Type (Sa-Sab) Spiral Galaxies|
We present a search for the signatures of galaxy-galaxy interactions inthe neutral gas of early-type spirals. New neutral hydrogen observationsfor four highly star-forming early-type spirals are presented here,along with H I data for three additional galaxies from other sources. HI maps of six of seven galaxies reveal unambiguous signs of a recentencounter, via tidal tails and H I bridges. Most of these galaxiesappear undisturbed in the optical, and these interactions probably wouldhave gone unnoticed without H I mapping. Such high rates of interactionsuggest that galactic encounters may play an important role in theevolution of early-type spiral galaxies.
|The cold gas properties of Markarian galaxies|
A 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.
|Far-Infrared Census of Starburst-Seyfert Connection|
Far-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.
|Rotation curves and metallicity gradients from HII regions in spiral galaxies|
In this paper we study long slit spectra in the region of Hαemission line of a sample of 111 spiral galaxies with recognizable andwell defined spiral morphology and with a well determined environmentalstatus, ranging from isolation to non-disruptive interaction withsatellites or companions. The form and properties of the rotation curvesare considered as a function of the isolation degree, morphological typeand luminosity. The line ratios are used to estimate the metallicity ofall the detected HII regions, thus producing a composite metallicityprofile for different types of spirals. We have found that isolatedgalaxies tend to be of later types and lower luminosity than theinteracting galaxies. The outer parts of the rotation curves of isolatedgalaxies tend to be flatter than in interacting galaxies, but they showsimilar relations between global parameters. The scatter of theTully-Fisher relation defined by isolated galaxies is significantlylower than that of interacting galaxies. The [NII]/Hα ratios, usedas a metallicity indicator, show a clear trend between Z andmorphological type, t, with earlier spirals showing higher ratios; thistrend is tighter when instead of t the gradient of the inner rotationcurve, G, is used; no trend is found with the change in interactionstatus. The Z-gradient of the disks depends on the type, being almostflat for early spirals, and increasing for later types. The[NII]/Hα ratios measured for disk HII regions of interactinggalaxies are higher than for normal/isolated objects, even if all thegalaxy families present similar distributions of Hα EquivalentWidth. Tables 3 and 4 and Figs. 6, 7 and 21 are only available inelectronic form at http://www.edpsciences.org. Table 5 is only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/389 Based on dataobtained Asiago/Ekar Observatory. Also based on observations made withINT operated on the island of La Palma by ING in the SpanishObservatorio del Roque de Los Muchachos of the Instituto deAstrofísica de Canarias.
|Recovering physical parameters from galaxy spectra using MOPED|
We derive physical parameters of galaxies from their observed spectrausing MOPED, the optimized data compression algorithm of Heavens,Jimenez & Lahav. Here we concentrate on parametrizing galaxyproperties, and apply the method to the NGC galaxies in Kennicutt'sspectral atlas. We focus on deriving the star formation history,metallicity and dust content of galaxies. The method is very fast,taking a few seconds of CPU time to estimate ~17 parameters, and istherefore specially suited to studying large data sets, such as theAnglo-Australian two-degree-field (2dF) galaxy survey and the SloanDigital Sky Survey (SDSS). Without the power of MOPED, the recovery ofstar formation histories in these surveys would be impractical. InKennicutt's atlas, we find that for the spheroidals a small recent burstof star formation is required to provide the best fit to the spectrum.There is clearly a need for theoretical stellar atmospheric models withspectral resolution better than 1Å if we are to extract all therich information that large redshift surveys contain in their galaxyspectra.
|Supernovae in the nuclear regions of starburst galaxies|
The feasibility of using near-infrared observations to discoversupernovae in the nuclear and circumnuclear regions of nearby starburstgalaxies is investigated. We provide updated estimates of the intrinsiccore-collapse supernova rates in these regions. We discuss the problemof extinction, and present new estimates of the extinction towards 33supernova remnants in the starburst galaxy M 82. This is done using Hiand H2 column density measurements. We estimate the molecularto atomic hydrogen mass ratio to be 7.4+/-1.0 in M 82. We have assemblednear-infrared photometric data for a total of 13 core-collapsesupernovae, some unpublished hitherto. This constitutes the largestdatabase of infrared light curves for such events. We show that theinfrared light curves fall into two classes, `ordinary' and `slowlydeclining'. Template JHKL light curves are derived for both classes. Forordinary core-collapse supernovae, the average peak JHKL absolutemagnitudes are -18.4, -18.6, -18.6 and -19.0 respectively. The slowlydeclining core-collapse supernovae are found to be significantly moreluminous than the ordinary events, even at early times, having averagepeak JHKL absolute magnitudes of -19.9, -20.0, -20.0 and -20.4respectively. We investigate the efficiency of a computerized imagesubtraction method in supernova detection. We then carry out a MonteCarlo simulation of a supernova search using K-band images of NGC 5962.The effects of extinction and observing strategy are discussed. Weconclude that a modest observational programme will be able to discovera number of nuclear supernovae.
|Strömgren Photometry from z=0 to z~1. I. The Method|
We use rest-frame Strömgren photometry to observe clusters ofgalaxies in a self-consistent manner from z=0 to z=0.8. Strömgrenphotometry of galaxies is intended as a compromise between standardbroadband photometry and spectroscopy, in the sense that it is moresensitive to subtle variations in spectral energy distributions than theformer, yet much less time-consuming than the latter. principalcomponent analysis is used to facilitate extraction of information fromthe Strömgren data. By calibrating the principal components usingwell-studied galaxies, as well as models of stellar populations, wedevelop a purely empirical method to detect, and subsequently classify,cluster galaxies at all redshifts smaller than 0.8. Interlopers arediscarded with unprecedented efficiency (up to 100%). The firstprincipal component essentially reproduces the Hubble sequence and canthus be used to determine the global star formation history of clustermembers. The (PC2, PC3) plane allows us to identify Seyfert galaxies(and distinguish them from starbursts) based on photometric colorsalone. In the case of E/S0 galaxies with known redshift, we are able toresolve the age-dust-metallicity degeneracy, albeit at the accuracylimit of our present observations. We use this technique in later papersto probe galaxy clusters well beyond their cores and to faintermagnitudes than spectroscopy can achieve, because the faint end of theluminosity function as well as the outer cluster regions seem to exhibitthe strongest evolutionary trends. We are able to directly compare thesedata over the entire redshift range without a priori assumptions becauseour observations do not require first-order k-corrections. Thecompilation of such data for different cluster types over a wideredshift range is likely to set important constraints on the evolutionof galaxies and on the clustering process.
|Chemo-spectrophotometric evolution of spiral galaxies - II. Main properties of present-day disc galaxies|
We study the chemical and spectrophotometric evolution of galactic discswith detailed models calibrated on the Milky Way and using simplescaling relations, based on currently popular semi-analytic models ofgalaxy formation. We compare our results with a large body ofobservational data on present-day galactic discs, including disc sizesand central surface brightness, Tully-Fisher relations in variouswavelength bands, colour-colour and colour-magnitude relations, gasfractions versus magnitudes and colours and abundances versus local andintegrated properties, as well as spectra for different galacticrotational velocities. Despite the extremely simple nature of ourmodels, we find satisfactory agreement with all those observables,provided that the time-scale for star formation in low-mass discs islonger than for more massive ones. This assumption is apparently incontradiction with the standard picture of hierarchical cosmology. Wefind, however, that it is extremely successful in reproducing majorfeatures of present-day discs, like the change in the slope of theTully-Fisher relation with wavelength, the fact that more massivegalaxies are on average `redder' than low-mass ones (a generic problemof standard hierarchical models) and the metallicity-luminosity relationfor spirals. It is concluded that, on a purely empirical basis, this newpicture is at least as successful as the standard one. Observations athigh redshifts could help to distinguish between the two possibilities.
|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.
|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.
|Hα Imaging of Early-Type (SA-SAB) Spiral Galaxies. I.|
Hα and continuum images are presented for 27 nearby early-type(Sa-Sab) spiral galaxies. Contrary to popular perception, the imagesreveal copious massive star formation in some of these galaxies. Adetermination of the Hα morphology and a measure of the Hαluminosity suggest that early-type spirals can be classified into twobroad categories based on the luminosity of the largest H II region inthe disk. The first category includes galaxies for which the individualH II regions have L_Hα<10^39 ergs s^-1. Most of the category 1galaxies appear to be morphologically undisturbed but show a widediversity in nuclear Hα properties. The second category includesgalaxies that have at least one H II region in the disk withL_Hα>=10^39 ergs s^-1. All category 2 galaxies show eitherprominent dust lanes or other morphological peculiarities such as tidaltails, which suggests that the anomalously luminous H II regions incategory 2 galaxies may have formed as a result of a recent interaction.The observations, which are part of an ongoing Hα survey, revealearly-type spirals to be a heterogeneous class of galaxies that areevolving in the current epoch. We have also identified some systematicdifferences between the classifications of spiral galaxies in the SecondGeneral Catalog and the Revised Shapley-Ames Catalog that may be tracedto subtle variations in the application of the criteria used forclassifying spiral galaxies. An examination of earlier studies suggeststhat perceptions concerning the Hubble-type dependence of star formationrates among spiral galaxies depends on the choice of catalog.
|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 Pico DOS Dias Survey Starburst Galaxies|
We discuss the nature of the galaxies found in the Pico dos Dias Survey(PDS) for young stellar objects. The PDS galaxies were selected from theIRAS Point Source catalog. They have flux density of moderate or highquality at 12, 25, and 60 μm and spectral indices in the ranges -3.00<= alpha(25, 12) <= + 0.35 and -2.50 <= alpha(60, 25) <=+0.85. These criteria allowed the detection of 382 galaxies, which are amixture of starburst and Seyfert galaxies. Most of the PDS Seyfertgalaxies are included in the catalog of warm IRAS sources by de Grijp etal. The remaining galaxies constitute a homogeneous sample of luminous[log F (L_B/L_ȯ) = 9.9 +/- 0.4] starburst galaxies, 67% of whichwere not recognized as such before. The starburst nature of the PDSgalaxies is established by comparing their L_IR/L_B ratios and IRAScolors with a sample of emission-line galaxies from the literaturealready classified as starburst galaxies. The starburst galaxies show anexcess of FIR luminosity, and their IRAS colors are significantlydifferent from those of Seyfert galaxies-99% of the starburst galaxiesin our sample have a spectral index alpha(60, 25) < -1.9. As opposedto Seyfert galaxies, very few PDS starbursts are detected in X-rays. Inthe infrared, the starburst galaxies form a continuous sequence withnormal galaxies. But they generally can be distinguished from normalgalaxies by their spectral index alpha(60, 25) > -2.5. This colorcutoff also marks a change in the dominant morphologies of the galaxies:the normal IRAS galaxies are preferentially late-type spirals (Sb andlater), while the starbursts are more numerous among early-type spirals(earlier than Sbc). This preference of starbursts for early-type spiralsis not new, but a trait of the massive starburst nucleus galaxies(Coziol et al.). As in other starburst nucleus galaxy samples, the PDSstarbursts show no preference for barred galaxies. No difference isfound between the starbursts detected in the FIR and those detected onthe basis of UV excess. The PDS starburst galaxies represent the FIRluminous branch of the UV-bright starburst nucleus galaxies, with meanFIR luminosity log (L_IR/L_ȯ) = 10.3 +/- 0.5 and redshifts smallerthan 0.1. They form a complete sample limited in flux in the FIR at 2 x10^-10 ergs cm^-2 s^-1.
|Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies|
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
|Global regularities in integrated galaxy spectra|
We have investigated some statistical properties of integrated spectraof galaxies from the Kennicutt spectrophotometric atlas. The input datafor the analysis are galaxy spectra sampled in 1300 bins between 3750and 6500Angstroms. We make use of Principal Component Analysis (PCA) toanalyse the 1300-dimensional space spanned by the spectra. Theirprojection on to the plane defined by the first two principalcomponents, the principal plane, shows that normal galaxies are in aquasi-linear sequence that we call the spectral sequence. We show thatthe spectral sequence is closely related to the Hubble morphologicalsequence. These results are robust in the sense that the reality of thespectral sequence does not depend on data normalization. The existenceof this sequence suggests that a single parameter may describe thespectrum of normal galaxies. We have investigated this hypothesis withthe Bruzual & Charlot models of spectral evolution. We show that,for single-age models (15 Gyr), the spectral sequence can beparametrized by the characteristic star formation time-scales of thedifferent morphological types. By examining the projection ofevolutionary tracks of normal galaxies on to the principal plane, weverify that the spectral sequence is also an evolutionary sequence, withgalaxy spectra evolving from later to earlier spectral types.Considering the close correspondence between the spectral andmorphological sequences, this leads us to speculate that galaxies mayevolve morphologically along the Hubble sequence, from Sm/Im to E.
|Mid-Infrared Continuum of Starburst Nuclei: Contribution from Hot Large Grains within H II Regions?|
The IRAS 12 and 25 mu m fluxes are compared with the Br gamma flux in asample of starburst nuclei. Good correlations are found between them.The subsequent analysis indicates the presence of two components in themid-infrared continuum: the nonthermal emission from "small grains"(<=100 A) which are heated transiently by nonionizing photons outsidethe H II regions and the thermal emission from "large grains" which areheated to ~140 K by ionizing, nonionizing, and Ly alpha photons insidethe H II regions. The small grains emitting at 12 mu m are depleted by~20% with respect to cirrus clouds in our Galaxy. The ratio of amountsof large grains to gas in the H II regions is comparable to the standardinterstellar value. The emission from hot large grains appears to bemore enhanced over the emission from small grains in starburst nucleiwith higher excitations.
|Population analysis of faint galaxies with mixture modeling.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114..958T&db_key=AST
|Massive Star Formation Along the Hubble Sequence|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..599D&db_key=AST
|An artificial neural network approach to the classification of galaxy spectra.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996MNRAS.283..651F&db_key=AST
|Optical and I-band surface photometry of spiral galaxies. I. The data.|
We present V- and I-band CCD surface photometry on 234 inclined Sa-Sdgalaxies, completed by similar data in B and R for a reduced subsample.In this first paper of a series, the reduction of the data is discussed,and several comparisons are made with other recent works. Radialprofiles are presented for the surface brightness and thecharacteristics of ellipses fitted to isophotes; global, effective, andisophotal parameters are listed. All the results are available inelectronic form.
|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.
|A multifrequency radio continuum and IRAS faint source survey of markarian galaxies|
Results are presented from a multifrequency radio continumm survey ofMarkarian galaxies (MRKs) and are supplemented by IRAS infrared datafrom the Faint Source Survey. Radio data are presented for 899 MRKsobserved at nu = 4.755 GHz with the National Radio Astronomy Observatory(NRAO)-Green Bank 300 foot (91 m) telescope, including nearly 88% ofthose objects in Markarian lists VI-XIV. In addition, 1.415 GHzmeasurements of 258 MRKs, over 30% of the MRKs accessible from theNational Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported.Radio continuum observations of smaller numbers of MRKs were made at10.63 GHz and at 23.1 GHz and are also presented. Infrared data from theIRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, withreasonably secure identifications extracted from the NASA/IPACExtragalactic Database. MRKs exhibit the same canonical infraredcharacteristics as those reported for various other galaxy samples, thatis well-known enhancement of the 25 micrometer/60 micrometer color ratioamong Seyfert MRKs, and a clear tendency for MRKs with warmer 60micrometer/100 micrometer colors to also possess cooler 12 micrometer/25micrometer colors. In addition, non-Seyfert are found to obey thewell-documented infrared/radio luminosity correlation, with the tightestcorrelation seen for starburst MRKs.
|Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies|
Multivariate data have been collected as part of an effort to develop anew classification system for spiral galaxies, one which is notnecessarily based on subjective morphological properties. A sample of492 moderately bright northern Sa and Sc spirals was chosen for futurestatistical analysis. New observations were made at 20 and 21 cm; thelatter data are described in detail here. Infrared Astronomy Satellite(IRAS) fluxes were obtained from archival data. Finally, new estimatesof arm pattern radomness and of local environmental harshness werecompiled for most sample objects.
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