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|The AMIGA sample of isolated galaxies. VI. Radio continuum properties of isolated galaxies: a very radio-quiet sample|
Context: This paper is part of a series that describes the results ofthe AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies)project, studying the largest sample of very isolated galaxies in thelocal Universe. Aims: The study of the radio properties of the AMIGAsample is intended to characterize the radio continuum emission for asample least affected by the local environment, thus providing areference against which less isolated and interacting samples can becompared. Methods: Radio continuum data at 325, 1420, and 4850 MHzwere extracted from the WENSS, NVSS/FIRST, and GB6 surveys,respectively. The source extractions have been obtained fromreprocessing the data and new detections added to the cross-matcheddetections with the respective survey catalogs. We focus on the completeAMIGA subsample composed of 719 galaxies. Results: A catalog of radiofluxes was obtained from the above four surveys. Comparison between theNVSS and FIRST detections indicates that the radio continuum is comingfrom disk-dominated emission in spiral galaxies, in contrast to theresults found in high-density environments where nuclear activity ismore frequent. The comparison of the radio continuum power with acomparable sample, which is however not selected with respect to itsenvironment, the Condon et al. UGC-SF sample of starforming fieldgalaxies, shows a lower mean value for the AMIGA sample. We haveobtained radio-to-optical flux ratios (R) using the NVSS radio continuumflux. The distribution of R for the AMIGA galaxies is consistent with asample dominated by radio emission from star formation (SF) and a smallnumber of active galactic nuclei (AGN), with less than 3% of the samplewith R > 100. We derived the radio luminosity function (RLF) andtotal power density of the radio continuum emission for the AMIGA sampleat 1.4 GHz, and compared them with results from other low-redshiftstudies. The Schechter fit of the RLF indicates a major weight of thelow-luminosity galaxies. Conclusions: The results indicate the verylow level of radio continuum emission in our sample of isolatedgalaxies, which is dominated by mild disk SF. It confirms thus the AMIGAsample as a suitable template to effectively quantify the role ofinteractions in samples extracted from denser environments.Full Table 2 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/485/475
|The AMIGA sample of isolated galaxies. V. Quantification of the isolation|
Context: The AMIGA project aims to build a well defined andstatistically significant reference sample of isolated galaxies in orderto estimate the environmental effects on the formation and evolution ofgalaxies. Aims: The goal of this paper is to provide a measure of theenvironment of the isolated galaxies in the AMIGA sample, quantifyingthe influence of the candidate neighbours identified in our previouswork and their potential effects on the evolution of the primarygalaxies. Here we provide a quantification of the isolation degree ofthe galaxies in this sample. Methods: Our starting sample is theCatalogue of Isolated Galaxies (CIG). We used two parameters to estimatethe influence exerted by the neighbour galaxies on the CIG galaxy: thelocal number density of neighbour galaxies and the tidal strengthaffecting the CIG galaxy. We show that both parameters together providea comprehensive picture of the environment. For comparison, thoseparameters have also been derived for galaxies in denser environmentssuch as triplets, groups and clusters. Results: The CIG galaxies show acontinuous spectrum of isolation, as quantified by the two parameters,from very isolated to interacting. The fraction of CIG galaxies whoseproperties are expected to be influenced by the environment is howeverlow (159 out of 950 galaxies). The isolated parameters derived for thecomparison samples gave higher values than for the CIG and we foundclear differences for the average values of the 4 samples considered,proving the sensitivity of these parameters. Conclusions: Theenvironment of the galaxies in the CIG has been characterised, using twocomplementary parameters quantifying the isolation degree, the localnumber density of the neighbour galaxies and the tidal forces affectingthe isolated galaxies. A final catalogue of galaxies has been producedand the most isolated of these galaxies are consequently appropriate toserve as a reference sample for the AMIGA project.Full Tables [see full text], [see full text] and [see full text]-[see full text] are available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (188.8.131.52) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/472/121 and fromhttp://www.iaa.es/AMIGA.html.
|The AMIGA sample of isolated galaxies. III. IRAS data and infrared diagnostics|
Aims.We describe the mid- (MIR) and far- (FIR) infrared properties of alarge (~1000) sample of the most isolated galaxies in the localUniverse. This sample is intended as a "nurture-free" zero point againstwhich more environmentally influenced samples can be compared. Methods: We reprocess IRAS MIR/FIR survey data using the ADDSCAN/SCANPIutility for 1030 out of 1050 galaxies from the Catalogue of IsolatedGalaxies (CIG) as part of the AMIGA project. We focus on diagnostics(FIR luminosity L_FIR, R=log(L_FIR/LB), and IRAS colours)thought to be sensitive to effects of environment or interaction. Results: The distribution of log(L_FIR) sharply peaks from 9.0-10.5,with very few (<2%) galaxies above 10.5. Review of available opticalimages of the most FIR luminous galaxies finds the majority likely to beinteracting systems missed in our earlier morphological reevaluation.The optically normalised luminosity diagnostic R=log(L_FIR/LB) shows a sharply peaked distribution between 0.0and -1.0. These results were compared to the magnitude limited sample ofthe Center for Astrophysics that was selected without environmentaldiscrimination. This modestly (e.g., compared to cluster, binary galaxy,and compact group samples) environmentally affected sample shows asignificantly higher mean log(L_FIR), and R, whereas the meanlog(LB) is the same. Our sample shows a strong L_FIR vs.LB correlation, with a slope steeper than one (L_FIR ∝LB1.41). Interacting galaxies were found abovethis correlation, showing an enhancement in L_FIR. With respect to theIRAS colours, we found higher F_60/F_100 values for ellipticals andlate-type galaxies than for spirals, indicating a higher dusttemperature. The mean value of F_60/F_100 was found to be lower than forinteracting samples from the literature. Conclusions: .The resultsindicate that the FIR emission is a variable enhanced by interaction,and that our sample probably shows the lowest possible mean value. Thisattests to the utility of our sample for defining a nurture-free zeropoint.
|The AMIGA sample of isolated galaxies. II. Morphological refinement|
We present a refinement of the optical morphologies for galaxies in theCatalog of Isolated Galaxies that forms the basis of the AMIGA (Analysisof the interstellar Medium of Isolated GAlaxies) project. Uniformreclassification using the digitized POSS II data benefited from thehigh resolution and dynamic range of that sky survey. Comparison withindependent classifications made for an SDSS overlap sample of more than200 galaxies confirms the reliability of the early vs. late-typediscrimination and the accuracy of spiral subtypes within Δ T =1-2. CCD images taken at the Observatorio de Sierra Nevada were alsoused to solve ambiguities in early versus late-type classifications. Aconsiderable number of galaxies in the catalog (n = 193) are flagged forthe presence of nearby companions or signs of distortion likely due tointeraction. This most isolated sample of galaxies in the local Universeis dominated by two populations: 1) 82% are spirals (Sa-Sd) with thebulk being luminous systems with small bulges (63% between types Sb-Sc)and 2) a significant population of early-type E-S0 galaxies (14%). Mostof the types later than Sd are low luminosity galaxies concentrated inthe local supercluster where isolation is difficult to evaluate. Thelate-type spiral majority of the sample spans a luminosity rangeMB-corr = -18 to -22 mag. Few of the E/S0 population are moreluminous than -21.0 marking the absence of the often-sought superL* merger (e.g. fossil elliptical) population. The rarity ofhigh luminosity systems results in a fainter derived M* forthis population compared to the spiral optical luminosity function(OLF). The E-S0 population is from 0.2 to 0.6 mag fainter depending onhow the sample is defined. This marks the AMIGA sample as unique amongsamples that compare early and late-type OLFs separately. In othersamples, which always involve galaxies in higher density environments,M^*_E/S0 is almost always 0.3-0.5 mag brighter than M^*_S, presumablyreflecting a stronger correlation between M* andenvironmental density for early-type galaxies.
|A Digital Archive of H I 21 Centimeter Line Spectra of Optically Targeted Galaxies|
We present a homogeneous compilation of H I spectral parametersextracted from global 21 cm line spectra for some 9000 galaxies in thelocal universe (heliocentric velocity-200
|Revised positions for CIG galaxies|
We present revised positions for the 1051 galaxies belonging to theKarachentseva Catalog of Isolated Galaxies (CIG). New positions werecalculated by applying SExtractor to the Digitized Sky Survey CIG fieldswith a spatial resolution of 1 arcsper 2. We visually checked theresults and for 118 galaxies had to recompute the assigned positions dueto complex morphologies (e.g. distorted isophotes, undefined nuclei,knotty galaxies) or the presence of bright stars. We found differencesbetween older and newer positions of up to 38 arcsec with a mean valueof 2 arcsper 96 relative to SIMBAD and up to 38 arcsec and 2 arcsper 42respectively relative to UZC. Based on star positions from the APMcatalog we determined that the DSS astrometry of five CIG fields has amean offset in (alpha , delta ) of (-0 arcsper 90, 0 arcsper 93) with adispersion of 0 arcsper 4. These results have been confirmed using the2MASS All-Sky Catalog of Point Sources. The intrinsic errors of ourmethod combined with the astrometric ones are of the order of 0 arcsper5.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/391
|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.
|Galaxy structures in the Hercules region|
216 redshifts have been obtained in a region of 981 sq deg south of theHercules supercluster. 172 of these redshifts are of galaxies withmpg less than or equal to 15.1, 110 of which had no previousvelocity measurement. 44 new redshifts are of galaxies fainter thanmpg = 15.1. With these new data we have been able to define asample in a vast region (approximately 1700 sq deg) around Herculeslimited to mpg less than or equal to 15.1 with a velocitycompleteness of 81.5%. 189 galaxies have been morphologically classifiedso that all galaxies in the sample with known velocity now also haveknown morphology. The magnitude limited sample, including 556 galaxies,is then used to identify and describe galaxy structures in the region.We find that the overdense volume is small, that its overall appearanceis that of a coral branch floating in a sea of nothing and that earlyand late type galaxies defined different structures.
|H I observations of galaxies in the Hercules supercluster. II - Additional UGC galaxies and galaxies in selected CGCG fields|
The second installment of a H I redshift survey in the region of theHercules supercluster is presented. This part of the survey presents 218H I spectra of galaxies selected from the UGC which extends thepreviously begun survey of UGC galaxies in that region. In addition,spectra of 136 galaxies from selected CGCG fields are given. The CGCGfields were chosen to cover the projected position of the Hercules void.Measured H I parameters from the spectra are given. This survey wasconducted for application of the Tully-Fisher relation to search forstreaming motion around the void in front of the supercluster. Theselection effects affecting such a search are discussed in detail.
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