Contents
Images
Upload your image
DSS Images Other Images
Related articles
Stellar populations in local star-forming galaxies - II. Recent star formation properties and stellar masses
We present the integrated properties of the stellar populations in theUniversidad Complutense de Madrid (UCM) Survey galaxies. Applying thetechniques described in the first paper of this series, we derive ages,burst masses and metallicities of the newly formed stars in our samplegalaxies. The population of young stars is responsible for the Hαemission used to detect the objects in the UCM Survey. We also infertotal stellar masses and star formation rates in a consistent way takinginto account the evolutionary history of each galaxy. We find that anaverage UCM galaxy has a total stellar mass of ~1010Msolar, of which about 5 per cent was formed in aninstantaneous burst that occurred about 5 Myr ago, and subsolarmetallicity. Less than 10 per cent of the sample shows massivestarbursts involving more than half of the total mass of the galaxy.Several correlations are found among the derived properties. The burststrength is correlated with the extinction and with the integratedoptical colours for galaxies with low obscuration. The current starformation rate is correlated with the gas content. A stellarmass-metallicity relation is also found. Our analysis indicates that theUCM Survey galaxies span a broad range in properties between those ofgalaxies completely dominated by current/recent star formation and thoseof normal quiescent spirals. We also find evidence indicating that starformation in the local Universe is dominated by galaxies considerablyless massive than L*.
| Stellar populations in local star-forming galaxies - I. Data and modelling procedure
We present an analysis of the integrated properties of the stellarpopulations in the Universidad Complutense de Madrid (UCM) Survey ofHα-selected galaxies. In this paper, the first of a series, wedescribe in detail the techniques developed to model star-forminggalaxies using a mixture of stellar populations, and taking into accountthe observational uncertainties. We assume a recent burst of starformation superimposed on a more evolved population. The effects of thenebular continuum, line emission and dust attenuation are taken intoaccount. We also test different model assumptions, including the choiceof specific evolutionary synthesis model, initial mass function, starformation scenario and the treatment of dust extinction. Quantitativetests are applied to determine how well these models fit ourmultiwavelength observations for the UCM sample. Our observations spanthe optical and near-infrared, including both photometric andspectroscopic data. Our results indicate that extinction plays a keyrole in this kind of study, revealing that low- and high-obscuredobjects may require very different extinction laws and must be treateddifferently. We also demonstrate that the UCM Survey galaxies are bestdescribed by a short burst of star formation occurring within aquiescent galaxy, rather than by continuous star formation. A detaileddiscussion on the inferred parameters, such as the age, burst strength,metallicity, star formation rate, extinction and total stellar mass forindividual objects, is presented in Paper II of this series.
| Spatial Analysis of the Hα Emission in the Local Star-forming UCM Galaxies
We present a photometric study of the Hα emission in theUniversidad Complutense de Madrid (UCM) Survey galaxies. This workcomplements our previously published spectroscopic data. We study thelocation of the star-forming knots, their intensity and concentration,and the relationship of these properties with those of the host galaxy.We also estimate that the amount of Hα emission that arises fromthe diffuse ionized gas is about 15%-30% of the total Hα flux fora typical UCM galaxy. This percentage seems to be independent of theHubble type. Conversely, we find that an ``average'' UCM galaxy harborsa star formation event with 30% of its Hα luminosity arising froma nuclear component. The implications of these results for higherredshift studies are discussed, including the effects of galaxy size andthe depth of the observations. A correlation between the star formationrate and the Balmer decrement is observed, but such correlation breaksdown for large values of the extinction. Finally, we recalculate theHα luminosity function and star formation rate density of thelocal universe using the new imaging data. Our results point out that,on average, spectroscopic observations detected about one-third of thetotal emission-line flux of a typical UCM galaxy. The new valuesobtained for the Hα luminosity density and the star formation ratedensity of the local universe are 1039.3+/-0.2 ergss-1 Mpc-3 andρSFR=0.016+0.007-0.004Msolar yr-1 Mpc-3 (H0=50 kms-1 Mpc-1, ΩM=1.0, Λ=0).The corresponding values for the ``concordance cosmology''(H0=70 km s-1 Mpc-1,ΩM=0.3, Λ=0.7) are 1039.5+/-0.2 ergss-1 Mpc-3 andρSFR=0.029+0.008-0.005Msolar yr-1 Mpc-3.
| Kinematics of AWM and MKW Poor Clusters
We have measured 1365 redshifts to a limiting magnitude of R~15.5 in 15AWM/MKW clusters and have collected another 203 from the literature inMKW 4s, MKW 2, and MKW 2s. In AWM 7 we have extended the redshift sampleto R~18 in the cluster center. We have identified 704 cluster members in17 clusters; 201 are newly identified. We summarize the kinematics anddistributions of the cluster galaxies and provide an initial discussionof substructure, mass and luminosity segregation, spectral segregation,velocity-dispersion profiles, and the relation of the central galaxy toglobal cluster properties. We compute optical mass estimates, which wecompare with X-ray mass determinations from the literature. The clustersare in a variety of dynamical states, reflected in the three classes ofbehavior of the velocity-dispersion profile in the core: rising,falling, or flat/ambiguous. The velocity dispersion of the emission-linegalaxy population significantly exceeds that of the absorption-linegalaxies in almost all of the clusters, and the presence ofemission-line galaxies at small projected radii suggests continuinginfall of galaxies onto the clusters. The presence of a cD galaxy doesnot constrain the global cluster properties; these clusters are similarto other poor clusters that contain no cD. We use the similarity of thevelocity-dispersion profiles at small radii and the cD-like galaxies'internal velocity dispersions to argue that cD formation is a localphenomenon. Our sample establishes an empirical observational baselineof poor clusters for comparison with simulations of similar systems.Observations reported in this paper were obtained at the Multiple MirrorTelescope Observatory, a facility operated jointly by the University ofArizona and the Smithsonian Institution; at the Whipple Observatory, afacility operated jointly by the Smithsonian Astrophysical Observatoryand Harvard University; and at the WIYN Observatory, a joint facility ofthe University of Wisconsin-Madison, Indiana University, YaleUniversity, and the National Optical Astronomy Observatories.
| Optical photometry of the UCM lists I and II. II. B band surface photometry and morphological discussion
We present Johnson B surface photometry for the UCM Survey galaxies.One-dimensional bulge-disk decomposition is attempted, discussing onfitting functions and computational procedures. The results from thisdecomposition, jointly with concentration indices and an asymmetrycoefficient, are employed to study the morphological properties of thesegalaxies. We also compare our results with the previous morphologicalclassification established using Gunn r imaging data and with othersamples of galaxies. No major statistical differences in morphology arefound between red and blue data, although some characteristics such assize and luminosity concentration vary. We find a correlation betweenluminosity and size. Several parameters are used to segregate theobjects according to their morphological type. Tables 2 and 3 are alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/365/370
| Star formation properties of Universidad Complutense de Madrid survey galaxies
We present new near-infrared J and K imaging data for 67 galaxies fromthe Universidad Complutense de Madrid (UCM) survey used in thedetermination of the SFR density of the local Universe by Gallego et al.This is a sample of local star-forming galaxies with redshift lower than0.045, and they constitute a representative subsample of the galaxies inthe complete UCM survey. From the new data, complemented with our ownGunn-r images and long-slit optical spectroscopy, we have measuredintegrated K-band luminosities, r-J and J-K colours, and Hαluminosities and equivalent widths. Using a maximum likelihood estimatorand a complete set of evolutionary synthesis models, these observationsallow us to estimate the strength of the current (or most recent) burstof star formation, its age, the star formation rate and the totalstellar mass of the galaxies. An average galaxy in the sample has astellar mass of 5×1010Msolar and isundergoing (or has recently completed) a burst of star formationinvolving about 2per cent of its total stellar mass. We identify twoseparate classes of star-forming galaxies in the UCM sample:low-luminosity, high-excitation galaxies (Hiilike) and relativelyluminous spiral galaxies (starburst disc-like). The former show higherspecific star formation rates (SFRs per unit mass) and burst strengths,and lower stellar masses than the latter. With regard to their specificstar formation rates, the UCM galaxies are intermediate objects betweennormal quiescent spirals and the most extreme Hii galaxies.
| Optical photometry of the UCM Lists I and II I. The data
We present Johnson B CCD photometry for the whole sample of galaxies ofthe Universidad Complutense de Madrid (UCM) Survey Lists I and II. Theyconstitute a well-defined and complete sample of galaxies in the LocalUniverse with active star formation. The data refer to 191 S0 to Irrgalaxies at an averaged redshift of 0.027, and complement the alreadypublished Gunn r, J and K photometries. In this paper the observationaland reduction features are discussed in detail, and the new colourinformation is combined to search for clues on the properties of thegalaxies, mainly by comparing our sample with other surveys. Tables 1and 3 are also available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html}
| Survey for Emission-Line Galaxies: Universidad Complutense de Madrid List 2
A low-dispersion objective-prism survey for low-redshift emission-linegalaxies (ELGs) is being carried out by the Universidad Complutense deMadrid with the Schmidt telescope at the German-Spanish Observatory ofCalar Alto (Almeria, Spain). A 4^deg^ full-aperture prism, whichprovides a dispersion of 1950 A mm^-1^, and IIIa-F emulsion combinationhas been used to search for ELGs selected by the presence of Hαemission in their spectra. A compilation of descriptions and positions,along with finding charts, is presented for 103 emission-line objects.This is the second list, which contains objects located in a region ofthe sky covering 201.4 deg^2^ in seven fields near α = 15^h^ andδ = 25^deg^.
| Observations of a complete sample of Hα emission-line galaxies. Long-slit spectroscopy of galaxies in UCM lists 1 and 2.
Spectroscopic observations for the full sample of Hα emission-linegalaxy candidates (ELGs) from the Universidad Complutense de Madridobjective-prism survey Lists 1 and 2 have been obtained in order toinvestigate fully the properties of the survey constituents as well asthe selection characteristics and completeness limits of the surveyitself. The spectroscopic data include redshifts, line fluxes,equivalent widths, emission-line ratios, optical reddening estimates andsynthesized color indexes. We find that 74% of the objects in thissample do exhibit emission lines. We compare our observational data withparameters given in the published survey lists in order to assess theusefulness of the latter. The different emission-line galaxies have beenclassified according to their spectra in several groups. Gray-scaleimages of the CCD spectra near the main emission lines, spatial profilesat the continuum and the line for [OIII] λ5007 and Hαlines, as well as plots of the coadded spectra of selected galaxies arepresented, and a number of peculiar objects are described.
| Photometric and morphological analysis of UCM galaxies. I. Observations and reductions. Morphological classifications.
We present the results of Thuan & Gunn r CCD imaging observations ofthe Universidad Complutense de Madrid (UCM) sample of emission-linegalaxies (ELGs), selected by the presence of Hα emission inlow-resolution objective prism spectra. In this work we characterizephotometrically and morphologically a total of 212 objects from the UCMsurvey. This Paper presents the observations and basic reductions, andlists a set of photometric parameters calculated for each UCM object. Inaddition, for the first time in a ELGs sample, we have determined themorphological classification of the objects using simultaneously fivedifferent criteria.
| IRAS observations of H-alpha selected emission-line galaxies
We present the results of IRAS observations of the UCM (UniversidadComplutense de Madrid) sample of emission-line galaxies, which have beenselected from wide-dispersion H-alpha objective-prism plates. These dataare intended to provide a convenient summary of the relevant FIRproperties of these galaxies. Color-color diagrams, as interpreted bytheoretical models, suggest that emission from UCM galaxies is mainlydue to dust heated directly by photons emitted in active star-formingregions. Statistical analysis of some samples, including the IRASminisurvey and blue-selected objective-prism samples, have beenperformed. Comparisons, based on FIR luminosity distributions, with theIRAS minisurvey make evident the lower metallicity of the CUM galaxieswhich cannot be considered as a parent population of IRAS-detectedgalaxies.
| A near-infrared imaging survey of interacting galaxies - The small angular-size ARP systems
Near-IR images of a large sample of interacting galaxies selected fromthe Atlas of Peculiar Galaxies by Arp (1966) have been obtained.Approximately 180 systems have been imaged in at least two, and usuallythree of the standard JHK bands. The survey and the observing and datareduction procedures, are described, and contour plots and aperturephotometry are presented. Future papers will analyze the imaging data bygroupings based on interaction type, stage, and progenitors. The goalsof the analysis are to explore the relationships between galaxyinteractions, activity, and morphology by studying the structure of thenear-IR luminosity distribution, where extinction effects are muchreduced relative to the optical and the major stellar mass component ofgalaxies dominates the observed light.
| Tests for alignment of galaxy position angles within a sheet of galaxies
Measured position angles of 149 galaxies that lie in a sheet near thevoid in Corona Borealis are presented. The distribution of positions andposition angles is tested for alignment; none is detected.
| KISO survey for ultraviolet-excess galaxies. II.
Not Available
| Atlas of interacting galaxies, Part. II and the concept of fragmentation of galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...28....1V&db_key=AST
| Atlas of Peculiar Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966ApJS...14....1A&db_key=AST
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
