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Nearby AGN and their hosts in the near infrared
We present near infrared ISAAC VLT observations of nine nearby (0.01≤ z ≤ 0.06) Active Galactic Nuclei selected from the Hamburg/ESOSurvey and the Véron-Cetty & Véron catalog. Hydrogenrecombination lines Paα and Brγ are observed in seven of thenine sources of which five show a broad component. In three sources,extended 1-0S(1) rotational-vibrational molecular hydrogen emission isdetected. Stellar CO absorption is seen in four sources. In one of theseobjects, an upper limit of the central mass can be determined from thestellar velocity field. H- and Ks-band imaging allow us to determine themorphology class of the host galaxies. Colors (with supplementary J-band2MASS images) show that the four galaxies with detected CO absorptionare characterized by an overall strong stellar contribution. One galaxyshows an increased extinction towards the nucleus. After removal of thenuclear point source, the host galaxies show colors typical fornon-active spiral galaxies.
| Small-Scale Systems of Galaxies. II. Properties of the NGC 4756 Group of Galaxies
This paper is part of a series that focuses on investigating galaxyformation and evolution in small-scale systems of galaxies inlow-density environments. We present results from a study of the NGC4756 group, which is dominated by the elliptical galaxy NGC 4756. Thecharacteristics of the group are investigated through (1) the detailedinvestigation of the morphological, photometric, and spectroscopicproperties of nine galaxies among the dominant members of the group; (2)the determination of the photometric parameters of the faint galaxypopulation in an area of 34'×34' centered onNGC 4756 and (3) an analysis of the X-ray emission in the area based onarchival data.The nine member galaxies are located in the core part of the NGC 4756group (a strip ~300 kpc in diameter, H0=70 km s-1Mpc-1), which has a very loose configuration. The centralpart of the NGC 4756 group contains a significant fraction of early-typegalaxies. Three new group members with previously unknown systemicvelocities are identified, one of which is type dE. At about 7.5 arcminsouthwest of NGC 4756 a substructure of the group is detected, includingIC 829, MCG -2-33-35, MCG -2-33-36, and MCG -2-33-38, that meets theHickson criteria for being a compact group. Most of the galaxies in thissubstructure show interaction signatures. We do not detect apparent finestructure and signatures of recent interaction events in the early-typegalaxy population, with the exception of a strong dust lane in theelliptical galaxy MCG -2-33-38. However, this galaxy displays signaturesof nuclear activity. Strong [O III], [N II], and [S II] line emission,combined with comparatively weak but broad Hα emission, suggestsan intermediate Seyfert type classification. Although the area isheavily contaminated by the background cluster A1631, X-ray data suggestthe presence of a hot intergalactic medium related to the detected X-rayemission of the group. The present results are discussed in the contextof group evolution.Based on observations obtained at the European Southern Observatory, LaSilla, Chile (program 65.P-252).
| Kinematics of the local universe . XII. 21-cm line measurements of 586 galaxies with the new Nançay receiver
This paper presents 586 new 21-cm neutral hydrogen line measurementscarried out with the FORT receiver of the meridian transit Nançayradiotelescope in the period July 2000-March 2003. This observationalprogramme is part of a larger project aiming at collecting an exhaustiveand magnitude-complete HI extragalactic catalogue for Tully-Fisherapplications. It is associated with the building of the MIGALEspectroscopic archive and database.Tables 2, 3 and HI-profiles and corresponding comments 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/430/373, or directly atour web site http://klun.obs-nancay.fr
| The B-band luminosities of quasar host galaxies
We report on the analysis of B-band imaging data of 57 low-redshiftquasi-stellar objects (quasars/QSOs) and Seyfert 1 galaxies selectedfrom the Hamburg/ESO Survey, for which host-galaxy-dependent selectionbiases are greatly reduced compared with other optical surveys. Only oneobject in the sample is known to be radio-loud.We adopted a procedure to remove the active galactic nuclei (AGN)contribution by subtracting a scaled point spread function from each QSOimage. To reclaim the integrated host galaxy flux we correct foroversubtraction based on simulations. This method is quite insensitiveto the host galaxy morphological type, which we can unambiguouslyestablish for 15 of the 57 objects.The quasar host galaxies are detected in all cases. The hosts are veryluminous, ranging in absolute magnitude MB from -19.0 to-23.8, with an average of MB,gal=-21.5, considerably above L*for field galaxies. For the luminous QSO subsample with MB< -23 the average host absolute magnitude is MB,gal=-23.0,while for the complementary low-luminosity AGN we obtainMB,gal=-21.2, roughly equal to L*.The luminous host galaxies in the sample are typically ~1 mag brighterthan expected when inferring B-band luminosities from studies of similarobjects at longer wavebands. We argue that this mismatch is not likelyto be explained by selection effects, but favours host galaxy colourssignificantly bluer than those of inactive galaxies. Although publishedB-band data are scant, this result and the findings of other authors arein good agreement.
| The Seyfert Population in the Local Universe
The magnitude-limited catalog of the Southern Sky Redshift Survey(SSRS2) is used to characterize the properties of galaxies hostingactive galactic nuclei (AGNs). Using emission-line ratios, we identify atotal of 162 (3%) Seyfert galaxies out of the parent sample with 5399galaxies. The sample contains 121 Seyfert 2 galaxies and 41 Seyfert 1galaxies. The SSRS2 Seyfert galaxies are predominantly in spirals oftypes Sb and earlier or in galaxies with perturbed appearance as theresult of strong interactions or mergers. Seyfert galaxies in thissample are twice as common in barred hosts as the non-Seyfert galaxies.By assigning galaxies to groups using a percolation algorithm, we findthat the Seyfert galaxies in the SSRS2 are more likely to be found inbinary systems when compared with galaxies in the SSRS2 parent sample.However, there is no statistically significant difference between theSeyfert and SSRS2 parent sample when systems with more than two galaxiesare considered. The analysis of the present sample suggests that thereis a stronger correlation between the presence of the AGN phenomenonwith internal properties of galaxies (morphology, presence of bar,luminosity) than with environmental effects (local galaxy density, groupvelocity dispersion, nearest neighbor distance).Partly based on observations at European Southern Observatory (ESO),under the ESO-ON agreement to operate the 1.52 m telescope.
| Gas Metallicity of Narrow-Line Regions in Narrow-Line Seyfert 1 Galaxies and Broad-Line Seyfert 1 Galaxies
We investigate gas metallicity of narrow-line regions in narrow-lineSeyfert 1 galaxies (NLS1's) and broad-line ones (BLS1's) in order toexamine whether or not there is a difference in the gas metallicitybetween the two populations of Seyfert 1 galaxies. We apply two methodsto study this issue. One is to use the emission-line flux ratio [N II]λ6583/Hαnarrow in combination with some otheroptical emission line flux ratios. This method, which has been oftenapplied to Seyfert 2 galaxies, suggests that the gas metallicity ofnarrow-line regions is indistinguishable, or possibly higher in BLS1'sthan in NLS1's. On the contrary, the other method, in which onlyforbidden emission line fluxes are used, results in that NLS1's tend topossess metal-richer gas in the narrow-line regions than BLS1's. Wepoint out that this inconsistency may be owing to the contamination ofthe narrow component of permitted lines by the broad component in thefirst method. Since the results derived by using only forbidden emissionline fluxes do not suffer from any uncertainty of the fitting functionfor the broad component of Balmer lines, the results from this methodare more reliable than those derived by using permitted lines. We thusconclude that the gas metallicity of narrow-line regions tends to behigher in NLS1's than in BLS1's.
| Visible and Near-Infrared Spectroscopy of Seyfert 1 and Narrow-Line Seyfert 1 Galaxies
This paper studies the continuum and emission-line properties of asample composed of 16 normal Seyfert 1 and seven narrow-line Seyfert 1(NLS1) galaxies using optical and near-IR CCD spectroscopy. Thecontinuum emission of the galaxies can be described in terms of acombination of stellar population, a nonstellar continuum of power-lawform, and Fe II emission. A significative difference in the opticalspectral index between NLS1's and normal Seyfert 1's is observed; thelatter is steeper. Most NLS1's show Fe II/Hβ ratios larger thanthose observed in the other Seyfert 1's. In the IRAS band, both groupsof galaxies have very similar properties. We have searched for thepresence of optically thin gas in the broad-line region (BLR) of thegalaxies by comparing the broad O I λ8446 and Hαemission-line profiles. Our analysis show that in the NLS1's, bothprofiles are similar in shape and width. This result contradicts thehypothesis of thin gas emission in the high-velocity part of the BLR toexplain the ``narrowness'' of broad optical permitted lines in theseobjects. Evidence of narrow O I λ8446 emission is found in sixgalaxies of our sample, implying that this line is not restricted to apure BLR phenomenon. In the narrow-line region, we find similarluminosities in the permitted and high-ionization lines of NLS1's andnormal Seyfert 1's. However, low-ionization lines such as [O I]λ6300, [O II] λ3727, and [S II] λλ6717, 6731are intrinsically less luminous in NLS1's. Physical properties derivedfrom density- and temperature-sensitive line ratios suggest that the [OII] and [S II] emitting zones are overlapping in normal Seyfert 1's andseparated in NLS1's. Based on observations made at CASLEO. ComplejoAstronómico El Leoncito (CASLEO) is operated under agreementbetween the Consejo Nacional de Investigaciones Científicas ytécnicas de la República Argentina and the NationalUniversities of La Plata, Córdoba and San Juán.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| The Southern Sky Redshift Survey
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
| Scaleheights of 486 southern spiral galaxies and some statistical correlation
Based on Peng's method (1988), we obtain scaleheights of 486 southernspiral galaxies, the images of which are taken from the Digitized SkySurvey at Xinglong Station of Beijing Astronomical Observatory. Thefitted spiral arms of 70 galaxies are compared with their images to gettheir optimum inclinations. The scaleheights of other 416 ones arelisted in Table A1 in Appendix. After compiling and analyzing the data,we find some statistical correlations. The most interesting results arethat a flatter galaxy is bluer and looks brighter, and galaxies becomeflatter along the Hubble sequence Sab -- Scd. Based on photographic dataof the National Geographic Society -- Palomar Observatory Sky Survey(NGS-POSS) obtained using the Oschin Telescope Palomar Mountain. TheNGS-POSS was funded by a grant from the National Geographic Society tothe California Institute of Technology. The plates were processed intothe present compressed digital form with their permission. The DigitizedSky Survey was produced at the Space Telescope Science Institute underUS Government grant NAG W-2166. Table A1 is available in electronic fromonly, via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| New southern galaxies with active nuclei. II.
This paper contains a list of new AGN candidates identified from theexamination of 3500 optical spectra contained in the database of theSouthern Sky Redshift Survey Extension (SSRS2). The classification ofgalaxies was done using standard diagnostics and a total of (5) Seyfert1, (12) Seyfert 2 and (10) LINERs were found. We also present a list of60 galaxies for which we could not secure a definite classification, butwhich might present some level of nuclear activity.
| The Hamburg/ESO survey for bright QSOs. II. Follow-up spectroscopy of 160 quasars and Seyferts.
We present a compilation of 160 QSOs and Seyfert 1 galaxies discoveredin the course of the Hamburg/ESO Survey. The QSOs were selected fromdigitised objective prism plates in 66 ESO/SRC fields. We give J2000 andB1950 positions, redshifts and blue magnitudes, and show high S/Nlow-resolution spectra. Redshifts are in the range 0<~z<~3.1, thecovered magnitude range is 14<~B<~18.
| Calan-Tololo survey. IV. Seyfert 1 galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994RMxAA..28..187M&db_key=AST
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