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Spectroscopic study of blue compact galaxies. V. Oxygen abundance and the metallicity-luminosity relation
This is the fifth paper in a series studying the stellar components,star formation histories, star formation rates and metallicities of ablue compact galaxy (BCG) sample. Based on our high-quality ground-basedspectroscopic observations, we have determined the electrontemperatures, electron densities, nitrogen abundances and oxygenabundances for 72 star-forming BCGs in our sample, using differentoxygen abundance indicators. The oxygen abundance covers the range 7.15< 12 + log (O/H)< 9.0, and nitrogen is found to be mostly aproduct of secondary nucleosynthesis for 12 + log (O/H)>8.2 andapparently a product of primary nucleosynthesis for 12 + log (O/H)<8.2. To assess the possible systematic differences among differentoxygen abundance indicators, we have compared oxygen abundances of BCGsobtained with the Te method, R23 method, P method,N2 method and O3N2 method. The oxygen abundances derived from theTe method are systematically lower by 0.1-0.25 dex than thosederived from the strong line empirical abundance indicators, consistentwith previous studies based on region samples. We confirm the existenceof the metallicity-luminosity relation in BCGs over a large range ofabundances and luminosities. Our sample of galaxies shows that the slopeof the metallicity-luminosity relation for the luminous galaxies(~-0.05) is slightly shallower than that for the dwarf galaxies(~-0.17). An offset was found in the metallicity-luminosity relation ofthe local galaxies and that of the intermediate redshift galaxies. Itshows that the metallicity-luminosity relation for the emission linegalaxies at high redshift is displaced to lower abundances, higherluminosities, or both.
| Spectroscopic study of blue compact galaxies. IV. Star formation rates and gas depletion timescales
This is the fourth paper in a series studying star formation rates,stellar components, metallicities, and star formation histories of ablue compact galaxy (BCG) sample. Using Hα, [O II]λ3727,infrared (IR), radio (1.4 GHz) luminosities and neutral hydrogen (H I)gas masses, we estimated star formation rates and gas depletiontimescales of 72 star-forming BCGs. The star formation rates of the BCGsin our sample span nearly four orders of magnitude, from approximately10-2 to 102 Mȯ yr-1,with a median star formation rate of about 3 Mȯyr-1. The typical gas depletion timescale of BCGs is aboutone billion years. Star formation could be sustained at the currentlevel only on a timescale significantly lower than the age of theuniverse before their neutral gas reservoir is completely depleted. Toassess the possible systematic differences among different starformation rate indicators, we compared the star formation rates derivedfrom Hα, [O II]λ3727, IR, and radio luminosities, andinvestigated the effects from underlying stellar absorption and dustextinction. We found that subtracting underlying stellar absorption isvery important to calculate both dust extinction and star formation rateof galaxies. Otherwise, the intrinsic extinction will be overestimated,the star formation rates derived from [O II]λ3727 and Hαwill be underestimated (if the underlying stellar absorption and theinternal extinction were not corrected from the observed luminosity) oroverestimated (if an overestimated internal extinction were used forextinction correction). After both the underlying stellar absorption andthe dust extinction were corrected, a remarkably good correlationemerges among Hα, [O II]λ3727, IR and radio star formationrate indicators. Finally, we find a good correlation between themeasured star formation rate and the absolute blue magnitude,metallicity, interstellar extinction of BCGs. Our results indicate thatfaint, low-mass BCGs have lower star formation rates.Star formation rates and gas depletion timescales of BCGs are availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/425/417
| Spectroscopic study of blue compact galaxies. III. Empirical population synthesis
This is the third paper of a series dedicated to the study of the starformation rates, star formation histories, metallicities and dustcontents of a sample of blue compact galaxies (BCGs). We constrain thestellar contents of 73 blue compact galaxies by analyzing theircontinuum spectra and the equivalent widths of strong stellar absorptionfeatures using a technique of empirical population synthesis based on alibrary of observed star-cluster spectra. Our results indicate that bluecompact galaxies are typically age-composite stellar systems; inaddition to young stars, intermediate-age and old stars contributesignificantly to the 5870 Å continuum emission of most galaxies inour sample. The stellar populations of blue compact galaxies also span avariety of metallicities. The ongoing episodes of star formation startedtypically less than a billion years ago. Some galaxies may be undergoingtheir first global episode of star formation, while for most galaxies inour sample, older stars are found to contribute up to half the opticalemission. Our results suggest that BCGs are primarily old galaxies withdiscontinuous star formation histories. These results are consistentwith the results from deep imaging observations of the color-magnitudediagrams of a few nearby BCGs using HST and large ground-basedtelescopes. The good quality of our population synthesis fits of BCGspectra allow us to estimate the contamination of the Hβox{Hα }, Hβ , Hγ and Hdelta Balmer emission lines bystellar absorption. The absorption equivalent widths measured in thesynthetic spectra range from typically 1.5 Å for Hβox{Hα }, to 2-5 Å for Hβ , Hγ , and Hdelta . Theimplied accurate measurements of emission-line intensities will be usedin a later study to constrain the star formation rates and gas-phasechemical element abundances of blue compact galaxies.
| Spectroscopic study of blue compact galaxies. II. Spectral analysis and correlations
This is the second paper in a series studying the star formation rates,stellar components, metallicities, and star formation histories andevolution of a sample of blue compact galaxies. We analyzed spectralproperties of 97 blue compact galaxies, obtained with the BeijingAstronomical Observatory (China) 2.16 m telescope, with spectral range3580 Å-7400 Å. We classify the spectra according to theiremission lines: 13 of the total 97 BCG sample are non-emission linegalaxies (non-ELGs); 10 have AGN-like emission (AGNs), and 74 of themare star-forming galaxies (SFGs). Emission line fluxes and equivalentwidths, continuum fluxes, the 4000 Å Balmer break index andequivalent widths of absorption lines are measured from the spectra. Weinvestigate the emission line trends in the integrated spectra of thestar-forming galaxies in our sample, and find that: 1) The equivalentwidths of emission lines are correlated with the galaxy absolute bluemagnitude MB; lower luminosity systems tend to have largerequivalent widths. 2) The equivalent width ratio [N II]6583/Hα isanti-correlated with equivalent width Hα; a relationship is giventhat can be used to remove the [N II] contribution from blendedHα+ [N II]6548, 6583. 3) The [O II], Hβ , Hγ andHα fluxes are correlated; those can be used as star formationtracers in the blue. 4) The metallicity indices show trends with galaxyabsolute magnitude and attenuation by dust, faint, low-mass BCGs havelower metallicity and color excess. Tables 1-4, and 6 are only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/396/503
| Spectroscopic study of blue compact galaxies. I. The spectra
Blue compact galaxies are compact objects that are dominated by intensestar formation. Most of them have dramatically different propertiescompared to the Milky Way and many other nearby galaxies. Using theIRAS, H I data, and optical spectra, we wanted to measure the currentstar formation rates, stellar components, metallicities, and starformation histories and evolution of a large blue compact galaxy sample.We anticipate that our study will be useful as a benchmark for studiesof emission line galaxies at high redshift. In the first paper of thisseries, we describe the selection, spectroscopic observation, datareduction and calibration, and spectrophotometric accuracy of a sampleof 97 luminous blue compact galaxies. We present a spectrophotometricatlas of rest-frame spectra, as well as tables of the recessionvelocities and the signal-to-noise ratios. The recession velocities ofthese galaxies are measured with an accuracy of delta V< 67 kms-1. The average signal-to-noise ratio of sample spectra is ~51. The spectral line strengths, equivalent widths and continuum fluxesare also measured for the same galaxies and will be analyzed in the nextpaper of this series. The atlas and tables of measurements will be madeavailable electronically. Table 3 and Fig. 4 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/845
| Stellar population synthesis for blue compact galaxies.
Not Available
| Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift
The evolution of the structure of galaxies as a function of redshift isinvestigated using two parameters: the metric radius of the galaxy(R_eta) and the power at high spatial frequencies in the disk of thegalaxy (chi). A direct comparison is made between nearby (z~0) anddistant (0.2<~z<~1) galaxies by following a fixed range in restframe wavelengths. The data of the nearby galaxies comprise 136broadband images at ~4500 Å observed with the 0.9 m telescope atKitt Peak National Observatory (23 galaxies) and selected from thecatalog of digital images of Frei et al. (113 galaxies). Thehigh-redshift sample comprises 94 galaxies selected from the Hubble DeepField (HDF) observations with the Hubble Space Telescope using the WideField Planetary Camera 2 in four broad bands that range between ~3000and ~9000 Å (Williams et al.). The radius is measured from theintensity profile of the galaxy using the formulation of Petrosian, andit is argued to be a metric radius that should not depend very stronglyon the angular resolution and limiting surface brightness level of theimaging data. It is found that the metric radii of nearby and distantgalaxies are comparable to each other. The median value of the radius ofthe local sample is ~5+/-1 kpc, and the median radius ofthe HDF sample is ~6+/-2 kpc for q_0=0.5, H_0=65 km s^-1Mpc^-1 however, for q_0=0.1, ~7 kpc and for q_0=1,~5 kpc. In the HDF, galaxies with redshifts larger thanz>0.6 have flatter R_eta distributions than galaxies with redshiftssmaller than z<=0.6. However, the median R_eta values of high- andlow-redshift galaxies are consistent with each other. This result isconsistent with the simulations of galaxy images at redshifts z=0.35,z=0.5, and z=0.9, which show that the metric sizes can be recoveredwithin +/-2 kpc. The flocculency or power at high spatial frequencies isquantified using a simple method that is based on surface photometry inone band and that depends on the size of the star-forming regions and onthe intensity profile of the galaxy. In nearby galaxies, the flocculencyis found to trace the star formation rate as chi is correlated withoptical colors (B-V) and the strength of the hydrogen recombinationlines (Hα). In the HDF, galaxies at redshifts smaller than z~1 andwith fluxes brighter than B=25 have values of chi similar to what ismeasured in nearby galaxies and to what is expected from simulations ofdistant galaxy images. Among the HDF galaxies, I find that at most 4%can be identified as dwarf galaxies with rates of star formation similarto NGC 4449 and NGC 1569. Most HDF galaxies are giants with starformation rates similar to those in nearby giant galaxies. In summary,in this study I have introduced a method to measure the metric sizes andflocculency of the two-dimensional light distribution of galaxies. As aresult, I find that the high spatial frequency power is related to thestar formation rate. Further, I find that the sizes and power at highspatial frequencies of HDF galaxies remain largely unchanged between thepresent epoch and redshifts lower than z~1.
| HI observations of blue compact galaxies from the first and second Byurakan surveys
We present the results of a neutral hydrogen survey of 79 galaxies froma statistical sample of 88 Blue Compact Galaxies (BCGs) selected fromthe First and Second Byurakan objective prism surveys to have a HIIregion-like spectrum, an equivalent width of the [O III] lambda 5007line larger than ~ 50 Å, and a velocity <= 6000 km s(-1) . Thedetection rate for the statistical sample is 74%. HI masses rangebetween 4 10(7)M_sun) and 5 10(9) M_sun with the HI mass distributionpeaking at 3 10(8) M_sun. The full width at half-maximum of the HIprofile varies between ~ 30 km s(-1) and 160 km s(-1) , with a mean of ~92 km s(-1) . These small widths are characteristic of dwarf galaxies.For comparison, we have also observed an additional 92 BCGs with weakerstar formation and/or larger distances, and/or interesting astrophysicalproperties. These in general have larger widths and HI masses.Tables~1,~2,~3 also available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Seyfert Galaxies. IV. Nuclear Profiles of Markarian Seyfert Galaxies from Hubble Space Telescope Images
We have examined the nuclear profiles of the Seyfert and non-SeyfertMarkarian galaxies in our near-infrared Hubble Space Telescope WF/PC-1snapshot survey. We find that nuclei of types 1-1.5 Seyfert galaxies aredominated by strong point sources, while those of Seyfert 2 and non-Seyfert Markarian galaxies tend to be resolved, less distinguished, andsimilar in shape to normal galaxy luminosity profiles. Two possibleinterpretations of this result for type 2 Seyfert galaxies are thattheir nuclear continuum sources are undetected in our bandpass,contributing less than 10% of the nuclear light (within 0.5 radius) inall cases or that their nuclear components are resolved and blend insmoothly with the brightness profile of the host galaxy's bulge. Sincespectroscopic studies support typical nuclear continuum fractionsdistinctly greater than 10%, the latter conclusion is clearlypreferable. If the continua observed in Seyfert 2 galaxies originate asnuclear light that is redirected into the line of sight by scattering,as predicted by unified models of active galactic nuclei, then thescattering regions must be extended. Simple simulations suggest thatthese regions must cover several tens of parsecs or more, in agreementwith estimates of the sizes of the scattering "mirrors" in other Seyfert2 galaxies. However, the similarity of the profiles of non-SeyfertMarkarian and type 2 Seyfert nuclei suggests that circumnuclear starformation may also be an important component in the nuclear profiles ofthe latter.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| 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.
| A survey of the Pisces-Perseus supercluster. VI - The declination zone +15.5 deg to 21.5 deg
New results are presented of Arecibo observations in the 21 cm line of765 galaxies with declinations between 15.5 deg and 21.5 deg, in thePisces-Perseus supercluster zone. If considered independently on theneighboring parts of sky, this region, to the South of the superclusterridge, shows significantly less evidence of structure on large scales inexcess of 30 Mpc, contrasting substantially with the characteristics ofthe declination zones immediately to the North.
| Pairing properties of Markarian starburst Galaxies
The environmental parameters of 516 non-Seyfert Markarian galaxies werestudied in a redshift-bounded sample, supplemented by new spectra andredshift measures for possible companions, in order to evaluate theiroccurrence in galaxy pairs, defined through quantitative criteria. Itwas found that one-third of these galaxies occur in pairs (while only 6to 10 percent of optically-selected galaxies are known to be paired). Acomparison of various optical and IR properties of paired and nonpairedMarkarian galaxies showed no differences in the shape of the optical,far-IR, or H-alpha luminosity functions. It was found, however, that theMarkarian component is brighter than the other galaxy in each pair by0.66 magnitude in the mean at B.
| Seyfert galaxies. II - Environments and IRAS colors
The environments of Seyfert galaxies are compared to the environments ofnon-Seyfert Markarian galaxies using galaxy counts obtained from thePalomar Observaory Sky Survey prints. While previous work by Dahari,confirmed here, indicates that Seyfert galaxies are more likely to haveclose companion galaxies than field galaxies, the Seyfert galaxiesexamined here have essentially the same environments as the comparisonsample of non-Seyfert Markarian galaxies. The IRAS colors of the Seyfertand non-Seyfert Markarian galaxies are used to distinguish betweenSeyfert activity and bursts of star formation. The results suggest thatclose companion galaxies enhance star formation rather than directlyenhancing Seyfert-like activity.
| Star-formation rates and forbidden O II emission in blue galaxies
Observations of forbidden O II 3727 A and H-beta emission-line strengthsare presented from large-aperture spectrophotometric observations ofnearby (z less than 0.1) optically blue galaxies covering a wide rangein surface brightness and luminosity. The forbidden O II emission-lineequivalent widths in these galaxies primarily lie between 30 and 100 A.Emission-line strengths in nearby blue galaxies thus resemble thosefound in faint galaxies at moderate-to-high redshifts. The most activelystar-forming nearby galaxies are characterized by surface brightness inthe forbidden O II line of about 10 to the -15th to 10 to the -14thergs/s per sq cm per sq arcsec over spatial distances of more than 1kpc. The fluxes of the forbidden O II and H-beta emission lines are wellcorrelated, and thus forbidden O II luminosities can be used to deriveapproximate star-formation rates in blue galaxies.
| Neutral hydrogen in starburst galaxies
A survey of neutral-hydrogen 21 cm emission from a sample of starburstgalaxies was conducted in order to derive their global properties. Ofthe 72 galaxies surveyed, H I was detected in 47. Average mass-to-lightratios log (MH/Lpg) = -0.7 + or - 0.4 and log (MT/Lpg) = 0.5 + or - 0.4.The masses and luminosities span the range 10 to the 10th-12th solarmasses and 10 to the 9th-11th solar luminosities, typical of normal latespirals. The starburst activity, as measured by the luminosity of theH-alpha line, correlates roughly with the mass of atomic hydrogen, thetotal mass, and the total photographic luminosity of the host galaxy. Itis suggested that the occurrence of a nuclear starburst and the strengthof such an event probably do not depend strongly on the large-scaleproperties of the galaxy.
| Stellar populations and star formation in irregular galaxies
A review and intercomparison is conducted of data on variousmorphologically-chosen groups of irregular galaxies in order tounderstand the underlying physical mechanisms that differentiate thesesystems. Particular attention is given to the observational clues to thestellar content, star-formation processes, and star-formation historiesof these galaxies, with an emphasis on the uncertainties and the manyunanswered questions.
| A catalog of Markarian galaxies
A catalog of Markarian galaxies is presented which tabulates redshifts,spectral and morphological classifications, magnitudes, infrared andradio flux densities, and over 600 references to available datapublished before January 1, 1986. Redshifts are now available for 1228objects with strong ultraviolet continua, and follow-up spectroscopicand photometric observations of Markarian galaxies have providedclassifications of 115 Seyfert 1, 43 Seyfert 2, and 137 starburst and HII-type galaxies. After a description of the Markarian survey and thecurrent catalog, a summary of the general results obtained from the datais presented. A preliminary study of the infrared properties ofMarkarian galaxies as measured by IRAS reveals a number of interestingresults, including the existence of a sample of elliptical andlenticular galaxies with appreciable infrared emission.
| Spectral and morphological investigation of the galaxies Markaryan 303 and 313
The results of a spectral and morphological investigation of thegalaxies Markaryan 303 and 313, whose spectra contain both emission andabsorption lines, are given. It is assumed that the absorption spectraof these galaxies have a stellar origin. It is concluded that on theaverage the stellar population of both objects is earlier than fornormal galaxies of the same morphological type.
| H I observations of blue compact galaxies
Neutral hydrogen observations, in the 21-cm line, of 99 compact galaxiesfrom the lists of Zwicky, Haro, and Markarian were made using the 91-and 305-m telescopes. Most were blue or very blue systems, and 72 weredetected. The overall global properties of these systems are found to bein approximately the same range as normal late-type galaxies. At oneextreme, however, they may extend to types later than Ir I systems.These systems are typically rich in H I gas, and there are indicationsthat they have large H I halos. It is suggested that H I gas infallingfrom such halos may provide the fuel for intermittent bursts of rapidstar formation and may explain the low metallicity found in some bluecompacts.
| Radio emission from some Markarian galaxies at 430 MHz
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..649T&db_key=AST
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