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An Imaging and Spectroscopic Survey of Galaxies within Prominent Nearby Voids. II. Morphologies, Star Formation, and Faint Companions
We analyze the optical properties of ~300 galaxies within and aroundthree prominent voids of the Center for Astrophysics Redshift Survey. Wedetermine CCD morphologies and Hα equivalent widths from ourimaging and spectroscopic survey. We also describe a redshift survey of250 neighboring galaxies in the imaging survey fields. We assess themorphology-density relation, EW(Hα)-density relation, and theeffects of nearby companions for galaxies in low-density environmentsselected with a smoothed large-scale (5 h-1 Mpc) galaxynumber density n. Both the morphological mix and the Hα line widthdistribution of galaxies at modest underdensities, 0.5R=16.13, demonstrates that the incidence ofa close companion in redshift space is insensitive to global densityover the range we investigate (0.163 σ) fromΔcz>~200 km s-1 at 0.5-1 at n<=0.5n. In the lowest densityenvironments, galaxies with companions clearly (~4 σ) havestronger star formation than comparable galaxies at larger globaldensity (0.5-1 kpc and 1000 km s-1) varies little over theentire density range. These results, combined with the luminosity- andcolor-density relations of this sample (Paper I), suggest that theformation and evolution of field galaxies are insensitive to large-scaleunderdensity down to a threshold of roughly half the mean density. Thedifferences in galaxy properties at the lowest global densities we canexplore (n<=0.5n) may be explained by (1) a relative scarcity of thesmall-scale primordial density enhancements needed to form massiveearly-type/absorption-line galaxies and (2) present-day galaxyencounters that are relatively more effective because of the lowervelocity dispersion on small scales (<~200 h-1 kpc) weobserve in these regions. In the voids, where the luminous galaxiespresumably formed more recently, there should be more gas and dustpresent for active star formation triggered by nearby companions.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| An Imaging and Spectroscopic Survey of Galaxies within Prominent Nearby Voids. I. The Sample and Luminosity Distribution
We study the optical properties of a large sample of galaxies inlow-density regions of the nearby universe. We make a 5 h-1Mpc smoothed map of the galaxy density throughout the Center forAstrophysics Redshift Survey (CfA2) to identify galaxies within threeprominent nearby ``voids'' with diameter >~30 h-1 Mpc. Weaugment the CfA2 void galaxy sample with fainter galaxies found in thesame regions from the more recent and deeper Century and Redshiftsurveys . We obtain B and R CCD images and high signal-to-noiselong-slit spectra for the resulting sample of 149 void galaxies, as wellas for an additional 131 galaxies on the periphery of these voids. Herewe describe the photometry for the sample, including B isophotalmagnitudes and B-R colors. For the 149 galaxies that lie in regionsbelow the mean survey density, the luminosity functions in B and R arewell fit by Schechter functions with respective parameters(αB=-0.5+/-0.3, B*=-18.9+/-0.2) and(αR=-0.9+/-0.3, R*=-20.4+/-0.3). The Bluminosity function (LF) is consistent with typical survey LFs (e.g.,the Southern Sky Redshift Survey), and the R LF is consistent with theCentury Survey. The B and R LFs of 131 galaxies in the ``voidperiphery''-regions between the mean density and twice the mean-havesimilar Schechter parameters. The CfA2 LF is inconsistent with bothsamples at the 3.5 σ level. When we narrow our analysis to the 46galaxies in regions below half the mean density, the LF is significantlysteeper: α~-1.4+/-0.5. The typical survey LFs are inconsistentwith this subsample at the ~2 σ level. The B-R color distributionof galaxies in the lowest density regions is also shifted significantly(~3 σ) blueward of the higher density samples. The most luminousred galaxies (R<~-21) are absent from the lowest density regions at the2.5 σ level.
| 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.
| The CfA Redshift Survey: Data for the NGP +36 Zone
We have assembled redshifts for a complete sample of 719 galaxies withm_zw_ <= 15.5 in the declination range 32.5^deg^ <= δ <=38.5^deg^ and right ascension range 8^h^ <= α <= 17^h^. Wehave determined morphological types for all galaxies in the magnitudelimited sample by direct inspection of the POSS-O plates. 576 of theredshifts are measurements from Mount Hopkins, and 405 are newredshifts. We also include new redshifts for 77 fainter galaxies in thesame strip.
| Corrections and additions to the third reference catalogue of bright galaxies
List of corrections and additions to the Third Reference Catalogue ofBright Galaxies (RC3) are given. The corrected version of the catalogue(RC3.9b), dated April 1994, is currently available through the nationaldata centers.
| A deep redshift survey of IRAS galaxies towards the Bootes void
Redshifts were measured for a complete sample of galaxies detected bythe IRAS within 11.5 deg of the center of the void in Bootes discoveredby Kirshner et al (1981). There are 12 IRAS galaxies within the void asdefined by the above authors, seven of which were discovered in thissurvey. One of these has a companion at the same redshift. The resultingdensity of IRAS galaxies in the void is measured to be between 1/6 and1/3 of the average density; the uncertainty is dominated by Poissonstatistics. Good agreement is found between the selection function andnumber density derived from the present sample and those derived fromthe all-sky sample of Strauss (1989). The optical spectra of the newlyfound galaxies in the void are typical of IRAS galaxies in the field.
| The case low-dispersion northern sky survey. IV - Galaxies in the Bootes void region
Positions, estimated magnitudes, and finding charts (when needed) areprovided for 424 blue and/or emission-line galaxies and 50 probable H IIregions in 21 galaxies contained within the region R.A. between 14 h 00m and 15 h 30 m and decl. between +33.0 deg and +56.0 deg (1950). Thesewere identified on low-dispersion, objective-prism plates taken with theBurrell Schmidt-type telescope at Kitt Peak. This sample, which includesgalaxies as faint as the 18th blue magnitude, should prove useful infurther studies of the Bootes void.
| KISO survey for ultraviolet-excess galaxies. I
Lists and identification charts of the ultraviolet-excess galaxies whichhave been detected on the multi-color plates taken with the Kiso Schmidttelescope are presented for the first 10 survey fields. Catalogued are573 objects, down to the photographic magnitude of about 17, in the skyarea of some 300 square degrees.
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