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H I observations of giant low surface brightness galaxies
We have used the Nançay Radio Telescope to obtain new global H Idata for 16 giant low surface brightness (LSB) galaxies. Our targetshave optical luminosities and disk scale lengths at the high end forspiral galaxies (LB~1010 Lsun andh_r>~ 6 kpc for H0=75 km s-1 Mpc-1),but they have diffuse stellar disks, with mean disk surface brightnessesga 1 magnitude fainter than normal giant spirals. Thirteen of thegalaxies previously had been detected in H I by other workers, but thepublished H I observations were either confused, resolved by thetelescope beam, of low signal-to-noise, or showed significantdiscrepancies between different authors. For the other 3 galaxies, no HI data were previously available. Several of the galaxies were resolvedby the Nançay \am{3}{6} E-W beam, so global parameters werederived from multiple-point mapping observations. Typical H I masses forour sample are >~ 1010 M_sun, withM_HI/LB=0.3-1.7 (in solar units). All of the observedgalaxies have published optical surface photometry, and we have compiledkey optical measurements for these objects from the literature. Wefrequently find significant variations among physical parameters ofgiant LSB galaxies reported by various workers. Tables 2 and 4 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/cgi-bin/qcat?J/A+A/365/1 Figure 2 and Tables3, 5 and 6 are only available in electronic form athttp://www.edpsciences.org
| The star formation histories of low surface brightness galaxies
We have performed deep imaging of a diverse sample of 26 low surfacebrightness galaxies (LSBGs) in the optical and the near-infrared. Usingstellar population synthesis models, we find that it is possible toplace constraints on the ratio of young to old stars (which weparametrize in terms of the average age of the galaxy), as well as themetallicity of the galaxy, using optical and near-infrared colours.LSBGs have a wide range of morphologies and stellar populations, rangingfrom older, high-metallicity earlier types to much younger andlower-metallicity late-type galaxies. Despite this wide range of starformation histories, we find that colour gradients are common in LSBGs.These are most naturally interpreted as gradients in mean stellar age,with the outer regions of LSBGs having lower ages than their innerregions. In an attempt to understand what drives the differences in LSBGstellar populations, we compare LSBG average ages and metallicities withtheir physical parameters. Strong correlations are seen between anLSBG's star formation history and its K-band surface brightness, K-bandabsolute magnitude and gas fraction. These correlations are consistentwith a scenario in which the star formation history of an LSBG primarilycorrelates with its surface density and its metallicity correlates withboth its mass and its surface density.
| Low Surface Brightness Galaxies in the Local Universe. I. The Catalog
Data are presented for 693 galaxies identified in a large new survey forlow surface brightness galaxies in the nearby universe (z <~ 0.1).The survey covers 786 square degrees centered on the equator, and itextends significantly the surface brightness range of galaxy surveys inwhich there are a substantial number of galaxies with redshifts. Thedata are derived from the Automated Plate Measuring machine scans ofsurvey plates from the UK Schmidt Telescope and from follow-upobservations at radio and optical wavelengths. Accurate positions, totalB magnitudes, surface brightness parameters, and angular sizes aretabulated for each galaxy. Radial velocities, optical luminosities, andneutral hydrogen masses are listed for a subset of the sample. Findingcharts are also presented for those objects having a large enoughangular size that the scans from survey plates provide somemorphological information. The selection function and the luminosityfunction that can be derived from the survey are discussed in twocompanion papers.
| Properties of the class of giant low surface brightness spiral galaxies
We have obtained CCD surface photometry and optical spectroscopy for asample of eight giant low surface brightness (LSB) spiral galaxiesdiscovered in the course of a large survey for LSB galaxies. We findthat these LSB giants have disks of larger scale length and lowercentral surface brightness than other spiral galaxies, although nonehave parameters as extreme as the prototype Malin 1. We find that theintegrated colors of these LSB giants are redder than the integratedcolors of smaller LSB galaxies, and that the LSB galaxies of all sizesfollow a relation between redder colors and increasing disk scalelength. Two of these eight LSB giants have active nuclei with the broadpermitted lines characteristic of a Seyfert 1 nucleus, and one has thenarrow lines of a Seyfert 2. The colors and absorption line indices ofthe bulges of these giants are indistinguishable from those of highsurface brightness (HSB) spirals, suggesting that their bulges havesimilar stellar populations and evolutionary histories. We also observedfour and detected three of these galaxies in the 21 cm line of H I.These LSB giants generally have high total H I masses, although none isas extreme as Malin 1. Finally, the small-scale environments aroundthese galaxies reveal several nearby companions. These LSB giants are atleast as likely as smaller LSB galaxies to have close companions, andtheir average number of neighbors approaches that of HSB galaxies.
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