Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
Kinematics of Interstellar Gas in Nearby UV-selected Galaxies Measured with HST STIS Spectroscopy
We measure Doppler shifts of interstellar absorption lines in HST STISspectra of individual star clusters in nearby UV-selected galaxies.Values for systemic velocities, which are needed to quantify outflowspeeds, are taken from the literature and verified with stellar lines.We detect outflowing gas in 8 of 17 galaxies via low-ionization lines(e.g., C II, Si II, Al II), which trace cold and/or warm gas. Thestarbursts in our sample are intermediate in luminosity (and mass) todwarf galaxies and luminous infrared galaxies (LIRGs), and we confirmthat their outflow speeds (ranging from -100 to nearly -520 kms-1, with an accuracy of ~80 km s-1) areintermediate to those previously measured in dwarf starbursts and LIRGs.We do not detect the outflow in high-ionization lines (such as C IV orSi IV); higher quality data will be needed to empirically establish howvelocities vary with the ionization state of the outflow. We do verifythat the low-ionization UV lines and optical Na I doublet give roughlyconsistent outflow velocities, solidifying an important link betweenstudies of galactic winds at low and high redshift. To obtain a highersignal-to-noise ratio (S/N), we create a local average compositespectrum and compare it to the high-z Lyman break composite spectrum. Itis surprising that the low-ionization lines show similar outflowvelocities in the two samples. We attribute this to a combination ofweighting toward higher luminosities in the local composite, as well asboth samples being, on average, brighter than the ``turnover''luminosity in the v-SFR relation.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained from the Data Archive at the Space Telescope Science Institute,which is operated by the Association of Universities for Research inAstronomy, Inc., under NASA contract NAS 5-26555. These observations areassociated with program GO-9036.
| The Stellar Content of Nearby Star-forming Galaxies. III. Unravelling the Nature of the Diffuse Ultraviolet Light
We investigate the nature of the diffuse intracluster ultraviolet lightseen in 12 local starburst galaxies, using long-slit ultravioletspectroscopy obtained with the Space Telescope Imaging Spectrograph(STIS) aboard the Hubble Space Telescope (HST). We take this faintintracluster light to be the field in each galaxy and compare itsspectroscopic signature with Starburst99 evolutionary synthesis modelsand with neighboring star clusters. Our main result is that the diffuseultraviolet light in 11 of the 12 starbursts lacks the strong O starwind features that are clearly visible in spectra of luminous clustersin the same galaxies. The difference in stellar features dominatingcluster and field spectra indicates that the field light comes primarilyfrom a different stellar population and not from scattering of UVphotons originating in the massive clusters. A cut along the spatialdirection of the UV spectra establishes that the field light is notsmooth but rather shows numerous ``bumps and wiggles.'' Roughly 30%-60%of these faint peaks seen in field regions of the closest (<4 Mpc)starbursts appear to be resolved, suggesting a contribution fromsuperpositions of stars and/or faint star clusters. Complementary WFPC2UVI imaging for the three nearest target galaxies, NGC 4214, NGC 4449,and NGC 5253, is used to obtain a broader picture and establish that allthree galaxies have a dispersed population of unresolved, luminous bluesources. Because the field spectra are dominated by B stars, we suggestthat the individual sources observed in the WFPC2 images are individualB stars (rather than O stars) or small star clusters. We considerseveral scenarios to understand the lack of observed massive stars inthe field and their implications for the origin of the field stellarpopulation. If the field stellar populations formed in situ, the fieldmust have either an IMF that is steeper than Salpeter (α~-3.0 to-3.5) or a Salpeter slope with an upper mass cutoff of 30-50Msolar. If star formation occurs primarily in star clusters,the field could be composed of older, faded clusters and/or a populationthat is coeval with the luminous clusters but lower in mass. We usethese benchmark populations to place constraints on the field stellarpopulation origin. Although the field probably includes stars ofdifferent ages, the UV light is dominated by the youngest stellarpopulations in the field. If the field is composed of older, dissolvingclusters, we estimate that star clusters (regardless of mass) need todissolve on timescales 7-10 Myr to create the field. If the field iscomposed of young clusters that fall below the detection limit ofindividual sources in our spectroscopy, they would have to be severalhundred solar masses or less, in order to be deficient in O stars,despite their extreme youth.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS5-26555.
| 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.
| NGC 3125-1: The Most Extreme Wolf-Rayet Star Cluster Known in the Local Universe
We use Space Telescope Imaging Spectrograph long-slit ultravioletspectroscopy of local starburst galaxies to study the massive starcontent of a representative sample of super-star clusters, with aprimary focus on their Wolf-Rayet (W-R) content as measured from the HeII λ1640 emission feature. The goals of this work are threefold.First, we quantify the W-R and O-star content for selected massive youngstar clusters. These results are compared with similar estimates madefrom optical spectroscopy available in the literature. We conclude thatthe He II λ4686 equivalent width is a poor diagnostic measure ofthe true W-R content. Second, we present the strongest known He IIλ1640 emission feature in a local starburst galaxy. This featureis clearly of stellar origin in the massive cluster NGC 3125-1, as it isbroadened (~1000 km s-1). Strong N IV λ1488 and N Vλ1720 emission lines commonly found in the spectra of individualW-R stars of WN subtype are also observed in the spectrum of NGC 3125-1.Finally, we create empirical spectral templates to gain a basicunderstanding of the recently observed strong He II λ1640 featureseen in Lyman break galaxies (LBGs) at redshifts z~3. The UV fieldobserved in local starbursts provides a good overall match to thecontinuum and weak photospheric features in LBGs in the spectral rangeλλ1300-1700 but cannot reproduce the He II λ1640emission seen in the composite LBG sample of Shapley et al. Anadditional (ad hoc) 10%-15% contribution from ``extreme'' W-R clusterssimilar to NGC 3125-1 on top of the field provides a good match to thestrength of this feature.Based on observations with the NASA ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS5-26555.
| 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 (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/515
| The evolution of stars and gas in starburst galaxies
In systems undergoing starbursts the evolution of the young stellarpopulation is expected to drive changes in the emission-line properties.This evolution is usually studied theoretically, with a combination ofevolutionary synthesis models for the spectral energy distribution ofstarbursts and photoionization calculations. In this paper we present amore empirical approach to this issue. We apply empirical populationsynthesis techniques to samples of starburst and HII galaxies in orderto measure their evolutionary state and correlate the results with theiremission-line properties. A couple of useful tools are introduced thatgreatly facilitate the interpretation of the synthesis: (1) anevolutionary diagram, the axes of which are the strengths of the young,intermediate age and old components of the stellar population mix; and(2) the mean age of stars associated with the starburst, . These toolsare tested with grids of theoretical galaxy spectra and found to workvery well even when only a small number of observed properties(absorption-line equivalent widths and continuum colours) is used in thesynthesis.Starburst nuclei and HII galaxies are found to lie on a well-definedsequence in the evolutionary diagram. Using the empirically defined meanstarburst age in conjunction with emission-line data, we have verifiedthat the equivalent widths of Hβ and [OIII] decrease for increasing. The same evolutionary trend was identified for line ratios indicativeof the gas excitation, although no clear trend was identified formetal-rich systems. All these results are in excellent agreement withlong-known, but little tested, theoretical expectations.
| 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.
| Estimating the Luminosity Function of M51-Type Galaxies
A new sample of M51-type galaxies consisting of 46 systems is used toestimate the B-band luminosity function. The luminosity function for theprimary components of the systems can be described by a Schechterfunction with the parameters * = (1.4±0.3)×10-5 Mpc-3, =-1.3+0.4 -0.3, and M * = -20.3+0.2 -0.1. The values of the latter twoparameters are comparable to those for isolated galactic pairs. Theresulting estimate of the average density of M51-type galaxies is(4±3)% of the average density of isolated pairs for luminositiesin the range -22m.0
| Star formation rate in galaxies from UV, IR, and Hα estimators
Infrared (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 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.
| 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.
| 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.
| Star formation and dust extinction in nearby star-forming and starburst galaxies
We 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.
| 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.
| 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.
| 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.
| The effect of dust on photometric redshift measurement: a self-consistent technique
A new method is developed for estimating photometric redshifts, usingrealistic template SEDs, extending over four decades in wavelength (i.e.from 0.05 μm to 1 mm). The template SEDs are constructed for fourdifferent spectral types of galaxies (elliptical, spiral, irregular andstarburst), satisfying the following characteristics: a) they arenormalised to produce the observed colours of galaxies at z ~ 0; b)incorporate the chemo-photometric spectral evolution of galaxies ofdifferent types, in agreement with the observations; c) allow treatmentof dust contribution and its evolution with redshift, consistent withthe spectral evolution models; d) include absorption and re-emission ofradiation by dust and hence, realistic estimates of the far-infraredradiation; e) include correction for inter-galactic absorption by Lymancontinuum and Lyman forest. Using these template SEDs, the photometricredshifts are estimated to an accuracy of Delta z = 0.11. Thesimultaneous and self-consistent modelling of both the photometric andchemical evolution of galaxies and the effect of dust, makes thistechnique particularly useful for high redshift galaxies. The effects onthe estimated photometric redshifts, due to assumptions in theevolutionary population synthesis models, are investigated anddiscussed. Also, the degeneracy in the predicted photometric redshiftsand spectral types are examined, using a simulated galaxy catalogue.Table~1 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/Abstract.html
| The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| Dust Absorption and the Ultraviolet Luminosity Density at Z~3 as Calibrated by Local Starburst Galaxies
We refine a technique to measure the absorption-corrected ultraviolet(UV) luminosity of starburst galaxies using rest-frame UV quantitiesalone and apply it to Lyman-limit U dropouts at z~3 found in the HubbleDeep Field (HDF). The method is based on an observed correlation betweenthe ratio of far-infrared (FIR) to UV fluxes with spectral slope beta (aUV color). A simple fit to this relation allows the UV flux absorbed bydust and reprocessed to the FIR to be calculated, and hence thedust-free UV luminosity to be determined. International UltravioletExplorer spectra and Infrared Astronomical Satellite fluxes of localstarbursts are used to calibrate the F_FIR/F_1600 versus beta relationin terms of A_1600 (the dust absorption at 1600 Å) and thetransformation from broadband photometric color to beta. Bothcalibrations are almost completely independent of theoreticalstellar-population models. We show that the recent marginal andnondetections of HDF U dropouts at radio and submillimeter wavelengthsare consistent with their assumed starburst nature and our calculatedA_1600. This is also true of recent observations of the ratio of opticalemission-line flux to UV flux density in the brightest U dropouts. Thislatter ratio turns out not to be a good indicator of dust extinction. InU dropouts, absolute magnitude M_1600,0 correlates with beta: brightergalaxies are redder, as is observed to be the case for local starburstgalaxies. This suggests that a mass-metallicity relationship is alreadyin place at z~3. The absorption-corrected UV luminosity function of Udropouts extends up to M_1600,0~-24 AB mag, corresponding to a starformation rate ~200 M_solar yr^-1 (H_0=50 km s^-1 Mpc^-3 and q_0=0.5 areassumed throughout). The absorption-corrected UV luminosity density atz~3 is rho_1600,0>=1.4x10^27 ergs^-1 Hz^-1 Mpc^-1. It is still alower limit since completeness corrections have not been done andbecause only galaxies with A_1600<~3.6 mag are blue enough in the UVto be selected as U dropouts. The luminosity-weighted meandust-absorption factor of our sample is 5.4+/-0.9 at 1600 Å.
| Molecular Gas in Strongly Interacting Galaxies. I. CO (1-0) Observations
We present observations of the CO (1-0) line in 80 interacting galaxiesas part of a program to study the role of interactions and mergers intriggering starbursts. The sample, which only includes obviouslyinteracting pairs of galaxies, is the largest such sample observed inCO. The observations were carried out at the NRAO 12 m and IRAM 30 mtelescopes. CO emission was detected in 56 galaxies (of which 32 are newdetections), corresponding to a detection rate of 70%. Because mostgalaxies are slightly larger than the telescope beam, correction factorswere applied to include CO emission outside the beam. The correctionfactors were derived by fitting a Gaussian function or an exponential CObrightness distribution to galaxies with multiple pointings and byassuming an exponential model for galaxies with single pointing. Wecompared the global CO fluxes of 10 galaxies observed by us at bothtelescopes. We also compared the measured fluxes for another 10 galaxiesobserved by us with those by other authors using the NRAO 12 m and FCRAO14 m telescopes. These comparisons provide an estimate of the accuracyof our derived global fluxes, which is ~40%. Mapping observations of twoclose pairs of galaxies, UGC 594 (NGC 317) and UGC 11175 (NGC 6621), arealso presented. In subsequent papers we will report the statisticalanalyses of the molecular properties in our sample galaxies and makecomparisons between isolated spirals and interacting galaxies.
| Tides, Interactions, and Fine-Scale Substructures in Galaxy Clusters
We present the results of a study on galaxy interactions, tides, andother processes that produce luminous fine-scale substructures in thegalaxy clusters: Coma, Perseus, Abell 2199, AWM 3, and AWM 5. Allunusual structures in these clusters can be categorized into sevenmorphologies: interacting galaxies, multiple galaxies (noninteracting),distorted galaxies, tailed galaxies, line galaxies, dwarf galaxy groups,and galaxy aggregates. The various morphologies are described, and acatalog is presented, of 248 objects in these five clusters along withcolor, and positional information obtained from CCD images taken withthe WIYN 3.5 m telescope in broadband B and R filters. Distorted,interacting, and fine-scale substructures have a range of colorsextending from blue objects with B-R~0 to redder colors at B-R~2.5. Wealso find that the structures with the most disturbed morphology havethe bluest colors. In addition, the relative number distributions ofthese structures suggest that two separate classes of galaxy clustersexist: one dominated by distorted structures and the other dominated bygalaxy associations. The Coma and Perseus clusters, respectively, areproposed as models for these types of clusters. These structures avoidthe deep potentials of the dominant D or cD galaxies in the Coma andPerseus clusters, and tend to clump together. Possible mechanisms forthe production of fine-scale substructure are reviewed and compared withobservations of z~0.4 Butcher-Oemler clusters. We conclude, based oncolor, positional, and statistical data, that the most likely mechanismfor the creation of these structures is through an interaction with thegravitational potential of the cluster, possibly coupled with effects ofweak interactions with cluster ellipticals.
| Starbursts in barred spiral galaxies. V. Morphological analysis of bars
We have measured the bar lengths and widths of 125 barred galaxiesobserved with CCDs. The dependence of bar strength (identified with baraxis ratio) on morphological type, nuclear activity, central and mid-barsurface brightness is investigated. The properties of the bars are bestexplained if the sample is divided into early- (< SBbc) and late-typegalaxies, and into active (starburst, Seyfert or LINER) and normalgalaxies. We find that galaxies with very long bars are mostly activeand that normal late-type galaxies have a distinct behavior from thethree other groups of galaxies. We confirm earlier findings that activelate-type galaxies tend to have both stronger and longer bars thannormal ones. An important result of this paper is that early-typegalaxies do not share this behavior: they all tend to have strong bars,whether they are active or not. We also find correlations between barstrength and relative surface brightness in the middle and at the edgeof the bar, which are not followed by normal late-type galaxies. Theseresults are interpreted in the light of recent numerical simulations andparadigms about galaxy evolution. They suggest that normal late-typegalaxies represent the first stage of galaxy evolution, and that bars inearly- and late-type galaxies do not have the same properties becausethey have a different origin. Based on observations obtained at the 2meter telescope of Observatoire du Pic du Midi, operated by INSU (CNRS)
| Ultraviolet spectral properties of magellanic and non-magellanic irregulars, H BT II and starburst galaxies
This paper presents the results of a stellar population analysisperformed on nearby (V_R<=5 000 km s^{-1}) star-forming galaxies,comprising magellanic and non-magellanic irregulars, H Ii and starburstgalaxies observed with the IUE satellite. Before any comparison ofgalaxy spectra, we have formed subsets according to absolute magnitudeand morphological classification. Subsequently, we have coadded thespectra within each subset into groups of similar spectral properties inthe UV. As a consequence, high signal-to-noise ratio templates have beenobtained, and information on spectral features can now be extracted andanalysed. Seven groups resulted from this procedure: the magellanicirregulars (including H Ii galaxies) produced two different bluespectral groups; the non-magellanic irregulars could be grouped into twospectral groups with rather peculiar properties; and the luminousstarbursts produced one flat and two blue template spectra. Theirstellar populations are analysed by means of a population synthesisalgorithm based on star cluster spectral components. The syntheticspectra reproduce the observed ones successfully (except thenon-magellanic irregular groups) both in terms of continuum distributionand spectral features. The synthesis flux fractions of different agegroups were transformed into mass fractions, allowing inferences on thestar formation histories. Young stellar populations (age <500 Myrs)are the main flux contributors; in a few cases the intermediate agepopulation (age~1 M_B-2 Myrs) is important, while the old bulgepopulation contributes at most with ~2 % of the lambda2646 Angstromsflux in the case of starburst galaxies, and is negligible in themagellanic irregulars. We also study the reddening values and theextinction law: an SMC-like extinction law is appropriate for all cases.Based upon data collected with the International Ultraviolet Explorer(IUE) Satellite, supported by NASA, SERC and ESA.
| The Supernova Rate in Starburst Galaxies
We conducted an optical CCD search for supernovae in a sample of 142bright [m(B) <= 16 mag], nearby (z<=0.03) starburst galaxies overthe period 1988 December to 1991 June, to a limiting R-band magnitude of18. Five supernovae were found, in all cases outside the host galaxy'snucleus. We determine supernova rates (in supernova units or SNU) in theextranuclear regions to be 0.7 h^2 SNU for Type Ia, 0.7 h^2 SNU for TypeIb/c, and ~0.6 h^2 SNU for Type II, with large uncertainties but upperlimits of 2.2 h^2, 2.5 h^2, and 1.7 h^2 SNU, respectively. These ratesare similar to those measured in ``normal'' galaxies. We found noevidence for a supernova-induced brightening in any galactic nucleusand, with a few reasonable assumptions, can place upper limits of 9 h^2,12 h^2, and 7 h^2 SNU on the rates of unobscured supernovae Types Ia,Ib/c, and II, respectively, inside the nuclei.
| The Ultraviolet Spectroscopic Properties of Local Starbursts: Implications at High Redshift
We report the results of a systematic study of the vacuum ultraviolet (lambda ~= 1150-2000 Angstroms) spectra of a sample of 45 starburst andrelated galaxies observed with the IUE satellite. These span broadranges in metallicity (from 0.02 to 3 times solar), bolometricluminosity (~107-4 x 1011 Lȯ), and galaxy properties (e.g.,including low-mass dwarf galaxies, normal disk galaxies, and massivegalactic mergers). The projected size of the IUE spectroscopic apertureis typically 1 to several kpc and therefore usually encompasses theentire starburst and is similar to the aperture sizes used forspectroscopy of high-redshift galaxies. Our principal conclusion is thatlocal starbursts occupy a very small fractional volume in themultidimensional manifold defined by such fundamental parameters as theextinction, metallicity, and vacuum-UV line strengths (both stellar andinterstellar) of the starburst and the rotation speed (mass) andabsolute magnitude of the starburst's "host" galaxy. More metal-richstarbursts are redder and more heavily extinguished in the UV, are moreluminous, have stronger vacuum-UV lines, and occur in more massive andoptically brighter host galaxies. We advocate using these localstarbursts as a "training set" to learn how to interpret the rest frameUV spectra of star-forming galaxies at high redshift better, and westress that the degree of similarity between local starbursts andhigh-redshift galaxies in this multidimensional parameter space canalready be tested empirically. The results on local starbursts suggestthat the high- redshift "Lyman Dropout" galaxies are typically highlyreddened and extinguished by dust (by an average factor of 5-10 in theUV), may have moderately high metallicities (0.1-1 times solar?), areprobably building galaxies with stellar surface-mass densities similarto present-day ellipticals, and may be suffering substantial losses ofmetal-enriched gas that can "pollute" the intergalactic medium.
| Surface Brightness of Starbursts at Low and High Redshifts
Observations in the rest-frame ultraviolet from various space missionsare used to define the nearby starburst regions having the highestsurface brightness on scales of several hundred parsecs. The brightlimit is found to be 6 x 10^-16 ergs cm^-2 s^-1 Å^-1 arcsec^-2 forrest-frame wavelength of 1830 Å. Surface brightness in thebrightest pixel is measured for 18 galaxies in the Hubble Deep Fieldhaving z > 2.2. After correcting for cosmological dimming, we findthat the high-redshift starbursts have intrinsic ultraviolet surfacebrightness that is typically 4 times brighter than low-redshiftstarbursts. It is not possible to conclude whether this difference iscaused by decreased dust obscuration in the high-redshift starburstregions or by intrinsically more intense star formation. Surfacebrightness enhancement of starburst regions may be the primary factorfor explaining the observed increase with redshift of the ultravioletluminosity arising from star formation.
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| Starbursts in barred spiral galaxies. III. Definition of a homogeneous sample of starburst nucleus galaxies
This paper presents optical long-slit spectroscopic observations of 105barred Markarian IRAS galaxies. These observations are used to determinethe spectral type (starburst or Seyfert) of emission-line regions in thenucleus and along the bar of the galaxies, in order to define ahomogeneous sample of Starburst Nucleus Galaxies (SBNGs). Our selectioncriteria (ultraviolet excess, far infrared emission and barredmorphology) have been very efficient for selecting star-forminggalaxies, since our sample of 221 emission-line regions includes 82%nuclear or extranuclear starbursts. The contamination by Seyferts is low(9%). The remaining galaxies (9%) are objects with ambiguousclassification (Hii or LINER). The dust content and Hα luminosityincrease towards the nuclei of the galaxies. No significant variation ofthe electron density is found between nuclear and bar Hii regions.However, the mean Hα luminosity and electron density in the barare higher than in typical disk Hii regions. We investigate differentmechanisms for explaining the excess of nitrogen emission observed inour starburst nuclei. There is no evidence for the presence of a weakhidden active galactic nucleus in our starburst galaxies. The cause ofthis excess is probably a selective enrichment of nitrogen in the nucleiof the galaxies, following a succession of short and intense bursts ofstar formation. Our sample of SBNGs, located at a mean redshift of ~0.015, has moderate Hα ( ~ 10(41) erg s(-1) ) and far infrared ( ~10(10) Lsun) luminosities. The types are distributed equallyamong early- and late-type giant spirals with a slight preference forSbc/Sc types because of their barred morphology. The majority (62%) ofSBNGs are isolated with no sign of gravitational interaction. In termsof distance, luminosity and level of interaction, SBNGs are intermediatebetween Hii galaxies and luminous infrared galaxies. Based onobservations obtained at the 1.93 meter telescope of Observatoire deHaute-Provence operated by INSU (CNRS). Tables 1, 3, 4, 5 and 6 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
Katalógusok és elnevezések:
|
