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The SCUBA Local Universe Galaxy Survey - III. Dust along the Hubble sequence
We present new results from the Submillimetre Common-User BolometerArray (SCUBA) Local Universe Galaxy Survey (SLUGS), the first largesystematic submillimetre (submm) survey of the local Universe. Since ourinitial survey of a sample of 104 IRAS-selected galaxies we have nowcompleted a survey of a sample of 81 optically selected galaxies,observed with the SCUBA camera on the James Clerk Maxwell Telescope.Since SCUBA is sensitive to the 90 per cent of dust too cold to radiatesignificantly in the IRAS bands our new sample represents the firstunbiased SCUBA survey of dust in galaxies along the whole length of theHubble sequence.We find little change in the properties of dust in galaxies along theHubble sequence, except a marginally significant trend for early-typegalaxies to be less-luminous submm sources than late types. Wenevertheless detected six out of 11 elliptical galaxies, although someof the emission may possibly be synchrotron rather than dust emission.As in our earlier work on IRAS galaxies we find that the IRAS and submmfluxes are well fitted by a two-component dust model with dustemissivity index β= 2. The major difference from our earlier workis that we find the ratio of the mass of cold dust to the mass of warmdust is much higher for our optically selected galaxies and can reachvalues of ~1000. Comparison of the results for the IRAS and opticallyselected samples shows that there is a population of galaxies containinga large proportion of cold dust that is unrepresented in the IRASsample.We derive local submm luminosity and dust mass functions, both directlyfrom our optically selected SLUGS sample, and by extrapolation from theIRAS Point Source Catalogue Redshift Survey (PSCz) survey using themethod of Serjeant and Harrison (by extrapolating the spectral energydistributions of the IRAS PSCz survey galaxies out to 850μm we probea wider range of luminosities than probed directly by the SLUGSsamples), and find excellent agreement between the two. We find them tobe well fitted by Schechter functions except at the highestluminosities. We find that as a consequence of the omission of coldgalaxies from the IRAS sample the luminosity function presented in ourearlier work is too low by a factor of 2, reducing the amount of cosmicevolution required between the low-z and high-z Universe.
| The distribution of atomic gas and dust in nearby galaxies - III. Radial distributions and metallicity gradients
The radial distribution of dust and gas in 38 nearby galaxies isinvestigated, using a sample of galaxies for which matched resolution(25 arcsec) neutral hydrogen (HI) and 850-μm images are available.Most of these radial profiles are fitted well by an exponential model,and the derived 850-μm scalelengths are proportional to the HIscalelengths. From this relation, it is found that the metallicitygradients of these galaxies are much shallower than previous studies,unless the dust temperature is constant within the disc, or asignificant component of molecular gas exists at large radii that is nottraced by CO observations.
| The distribution of atomic gas and dust in nearby galaxies - II. Further matched-resolution Very Large Array H I and SCUBA 850-μm images
We present Very Large Array (VLA) C-array 21-cm HI images of galaxiesfrom the SCUBA Local Universe Galaxy Survey which have been observed at850 μm with the James Clerk Maxwell Telescope. Matched-resolution (~25 arcsec) HI images of 17 galaxies are presented and compared with850-μm images. HI or 850-μm images of an additional six galaxieswhich were detected at only one wavelength are presented. Additionally,lower resolution H I observations of nine galaxies are presented. Theobservations of these galaxies, along with results previously presented,do not show any obvious trends in the HI/dust or H2/dust massratios with morphological type.
| 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 QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| 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.
| A Three-dimensional Diagnostic Diagram for Seyfert 2 Galaxies: Probing X-Ray Absorption and Compton Thickness
We present and discuss a three-dimensional diagnostic diagram forSeyfert 2 galaxies obtained using X-ray and [O III] data on a largesample of objects (reported in the Appendix). The diagram shows theKalpha iron line equivalent width as a function of both the columndensity derived from the photoelectric cutoff and the 2-10 keV fluxnormalized to the [O III] optical-line flux (the latter corrected forextinction and assumed to be a true indicator of the source intrinsicluminosity). We find that the hard X-ray properties of type 2 objectsdepend on a single parameter, the absorbing column density along theline of sight, in accordance with the unified model. The diagram can beused to identify Compton-thick sources and to isolate and study peculiarobjects. From this analysis we have obtained a column densitydistribution of Seyfert 2 galaxies that is thought to be a goodapproximation of the real distribution. A large population of heavilyabsorbed objects is discovered, including many Compton-thick candidates.Our results indicate that the mean log N_H cm^-2 in type 2 Seyfertgalaxies is 23.5 and that as many as 23%-30% of sources haveN_H>=10^24 cm^-2.
| Large-Scale Outflows in Edge-on Seyfert Galaxies. III. Kiloparsec-Scale Soft X-Ray Emission
We present ROSAT PSPC and HRI images of eight galaxies selected from adistance-limited sample of 22 edge-on Seyfert galaxies. Kiloparsec-scalesoft X-ray nebulae extend along the galaxy minor axes in three galaxies(NGC 2992, NGC 4388, and NGC 5506). The extended X-ray emission has0.2-2.4 keV X-ray luminosities of 0.4-3.5 x 1040 ergs s-1. The X-raynebulae are roughly cospatial with the large-scale radio emission,suggesting that both are produced by large-scale galactic outflows.Assuming pressure balance between the radio and X-ray plasmas, the X-rayfilling factor is >~104 times larger than the radio plasma fillingfactor, suggesting that large-scale outflows in Seyfert galaxies arepredominantly winds of thermal X-ray-emitting gas. We favor aninterpretation in which large-scale outflows originate as activegalactic nucleus-driven jets that entrain and heat gas on kiloparsecscales as they make their way out of the galaxy. Active galacticnucleus- and starburst-driven winds are also possible explanations incases where the winds are oriented along the rotation axis of the galaxydisk.
| High-Energy Spectra of Active Galactic Nuclei. II. Absorption in Seyfert Galaxies
Absorption by cold material in a large sample of active galaxies hasbeen analyzed in order to study statistically the behavior of absorbedsources. The analysis indicates that on the basis of the column densityalone, sources can be divided into low-absorption([N_{{H}}/N_{{H}_{{Gal}}}]<=50) and high-absorption([N_{{H}}/{N}_{{H}_{{Gal}}}]>=50) objects. While the second groupconsists mostly of narrow emission line galaxies (Seyfert galaxies oftype 1.9-2), the first group is less homogenous, being formed by amixture of broad and narrow emission line objects (Seyfert 1-2galaxies). A study of the distribution of the column density values bymeans of bootstrap analysis confirms the reality of this effect. Onegroup consisting of optically selected objects is well explained withinthe unified theory as nuclei obscured by a molecular torus. The secondgroup made up of X-ray- and IRAS-selected objects is more difficult todefine: in these sources the absorption is underestimated owing todifficulties (1) in fitting complex absorption spectra or (2) inmeasuring NH values in Compton-thick sources or the absorption has adifferent origin than in the torus. Possible correlations of absorptionwith X-ray luminosity, axial ratio, and Balmer decrement have also beeninvestigated. Previous suggestions that lower luminosity AGNs tend to bemore highly absorbed than those with higher luminosity are not confirmedby the present data; neither is any evidence for a correlation of NHwith axial ratio (b/a) found except for a preference of Seyfert 1-1.5galaxies to be in face-on galaxies. While some sources (Seyfert 1-1.5galaxies and low-absorption objects) have X-ray absorption compatiblewith Balmer decrement, high-absorption objects have column densitiesmuch higher than predicted from optical observations. These results arein agreement with the unified theory since the torus parameters areexpected to be independent of luminosity, its orientation should berandom with respect to the host galaxy, and its location should be inbetween the broad- and narrow-line regions. A study of the NHvariability indicates that in a large fraction (70%) of the sources forwhich the analysis could be done, NH varies on timescales from months toyears. In Seyfert 1-1.5 galaxies, the variability is associated with aregion in or near the broad-line region and is explained in terms ofpartial covering and/or warm absorption models. In Seyfert 2 galaxies,the only variability observed is that associated with narrow emissionline galaxies. The study of the column density distributions indicatesthat Seyfert 1-1.5 galaxies are characterized byN_{{H}}=18^{+9}_{-7}x1021 atoms cm-2. Seyfert 1.9-2 galaxieshave instead N_{{H}}=96^{+54}_{-35}x1021 atoms cm-2 and alarger dispersion; if this group is divided into low- andhigh-absorption objects, N_{{H}}=14.5^{+7.2}_{-5.3}x1021atoms cm-2 and N_{{H}}=132.8^{+80.1}_{-52.6} x 1021 atoms cm-2,respectively, are obtained. The observed dispersion in each group isconsistent with being entirely due to column density variability.
| A Search for H 2O Maser Emission toward Active Galactic Nuclei: Discovery of a Nuclear Maser Source in NGC 3735
We report the results of a survey for H2O maser emission in the 616--523transition at 1.35 cm wavelength in 29 active galactic nuclei (AGNs).One new maser was detected. The detection rate among objects withrecessional velocities <7000 km s-1 is consistent with rates reportedelsewhere for similarly nearby objects (about one in 15). The new maserlies in the edge-on Seyfert 2 galaxy NGC 3735 (inclination 77 deg)within 10 km s-1 of the systemic velocity. No other emission has beenidentified at velocities within +/-500 km s-1 of the systemic velocity.The maser is coincident with the radio continuum peak of the nucleus at6 and 3.6 cm wavelengths to within the estimated 1 sigma astrometricuncertainty of 0."1 (15 pc at a distance of 30 Mpc).
| Unified theories of active galactic nuclei: a hard X-ray sample of Seyfert 2 galaxies
We have re-analysed the Ginga 2-18 keV X-ray observations of Seyfert 2galaxies, and find that their mean spectrum can be described by a powerlaw of index alpha~1, reflection from an optically thick accretion discand/or molecular torus, and absorption from cold material. These objectsthen have a mean intrinsic spectrum similar to that of Seyfert 1s, andso support the predictions of orientation-dependent Seyfert unificationschemes. There is also an intrinsic dispersion about this mean spectrumwhich is similar to that seen in the Seyfert 1s. We demonstrate thisdispersion explicitly in several objects with data of highsignal-to-noise ratio, where the intrinsic spectra are much flatter orsteeper than alpha~1 despite the inclusion of neutral reflection,ionized reflection, unobscured reflection and/or ionized absorption.This is important, as a currently popular explanation for the Seyfert 1spectra (and hence the Seyfert 2 spectra presented here) is that ofHaardt & Maraschi, in which the UV seed photons for Compton coolingof the energetic electrons are produced from reprocessing of the hardX-ray spectrum in an accretion disc. This feedback model correctlypredicts the observed mean spectral index of alpha~1 for a wide range ofoptical depths. Steeper spectra than this can be produced naturally inthese models if the thermal plasma optical depth approaches unity or ifthere is intrinsic emission from the disc itself. However, such modelsare unable easily to explain intrinsic spectra much flatter thanalpha~1. Thus the flat-spectrum sources presented here, which are mostreminiscent of the atypical Seyfert galaxy NGC 4151, pose seriousproblems for the Haardt & Maraschi model if there are no otherexternal processes modifying the hard X-ray spectra in Seyfert galaxies.
| A Multiwavelength Catalog of Seyfert 2 Galaxies Observed in the 2--10 keV Energy Band
This paper is a catalog of Seyfert 2 galaxies observed in the 2-10 keVband (339 flux entries). In total, it contains data on 150 objects; for76 objects, a positive detection is reported, while for the remainingsources, 2 σ upper limits to the X-ray emission are given. Most ofthe data have been collected from the literature over a period startingfrom 1974 up to the middle of 1995. Accurate searches of literature anddatabases were performed for all objects, and frequently spectral fitswere reevaluated in order to make the data in the catalog uniform andcomplete. Some unpublished data are also included. For six objects,EXOSAT/ME date have been extracted from the satellite database andanalyzed; the 13 fluxes obtained have been added to the present catalog.The compilation of hard X-ray data has been complemented with data inthe soft (0.1-3 keV) X-ray band, as well as in ultraviolet (1450 A),optical (5500 A), infrared (3.5, 12, 25, 60, 100 micron), and radio (6cm) bands. Fluxes of the [O II] λ5007 and Hβ emission linesas well as the Balmer decrement Hα/Hβ, and axial ratio a/bare also given. The present database is meant to be a useful tool forthe study of the Seyfert 2 phenomenon in its various aspects.
| Large-Scale Outflows in Edge-on Seyfert Galaxies. I. Optical Emission-Line Imaging and Optical Spectroscopy
We have launched a search for large-scale (>1 kpc) minor axisoutflows in edge-on Seyfert galaxies in order to assess their frequencyof occurrence and to study their properties. Here we present opticalcontinuum and Hα + [N II] line images and/or minor axis long-slitspectra of 22 edge-on Seyfert galaxies. Six of these galaxies show atleast one of the following: (i) bi-symmetric Hα halos extendingalong the minor axis, (ii) bright emission-line complexes at distances> 4 kpc (in projection) out of the disk, and (iii) double-peakedemission- line profiles from the gas along the minor axis, suggestingthat a windblown bubble is present. Our results indicate that > 1/4of Seyfert galaxies have good evidence for minor axis galactic outflows.Kinetic luminosities of the galactic outflows in our sample Seyfertgalaxies are ~10^40^-10^42^ ergs s^-1^, assuming all the observed minoraxis emission is produced by the outflow. These values are, in general,~0.1 as large as those well-studied cases of superwinds in starburstgalaxies (Heckman, Armus, & Miley 1990). However, far-infraredluminosities of our sample Seyfert galaxies are also ~0.1 as large. Bothstarburst-driven superwinds and wide-angled outflows from the activegalactic nucleus are possible explanations for the observed large-scaleoutflows.
| Large-Scale Outflows in Edge-on Seyfert Galaxies. II. Kiloparsec-Scale Radio Continuum Emission
We present deep images of the kiloparsec-scale radio continuum emissionin 14 edge-on galaxies (10 Seyfert and four starburst galaxies).Observations were taken with the VLA at 4.9 GHz (6 cm). The Seyfertgalaxies were selected from a distance-limited sample of 22 objects(defined in the first paper in this series). The starburst galaxies wereselected to be well matched to the Seyferts in radio power, recessionalvelocity, and galaxy disk inclination angle. All four starburst galaxieshave a very bright disk component, and one (NGC 3044) has a radio halothat extends several kiloparsecs out of the galaxy plane. Six of the 10Seyferts observed have large-scale (radial extent > 1 kpc) radiostructures extending outward from the nuclear region, indicating thatlarge-scale outflows are quite common in Seyferts. Large-scale radiosources in Seyferts are similar in radio power and radial extent toradio halos in edge-on starburst galaxies, but their morphologies do notresemble spherical halos observed in starburst galaxies. The sourceshave diffuse morphologies, but, in general, they are oriented at skewedangles with respect to the galaxy minor axes. This result is most easilyunderstood if the outflows are AGN-driven jets that are somehow divertedaway from the galaxy disk on scales > 1 kpc. Starburst-driven winds,however, cannot be ruled out. More observational work is needed todetermine whether massive star formation is present at high enough ratesto drive galactic winds out to kiloparsec scales in Seyfert galaxies.
| 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 volume-limited sample of IRAS galaxies to 4000 km/s, 3: CCD photometry from Palomar and Tololo observatories
An all-sky, quasi-volume-limited sample of 251 spiral galaxies within4000 km/s has been extracted from the redshift survey of InfraredAstronomy Satellite (IRAS) galaxies by Strauss (1992). Distance modulifor these objects estimated via the Tully-Fisher (TF) method allow thepeculiar velocity field and the cosmological density parameter to beconstrained within this volume. The TF relation we exploit relatesdeprojected neutral hydrogen line width to near-infrared luminosity.Herein we present I and V band photometry for 159 members of this sampleobtained with charge coupled device (CCD) cameras at Palomar and Tololoobservatories. Image processing and photometric calibration proceduresare described. Twenty seven objects with multiple calibratedobservations suggest that isophotal I band magnitudes are reproduced toequal to or less than 0.05 mag precision at sigmaI = 23.5 magarcsec-2, and that systematic run-to-run offsets are limitedto equal to or less than 0.05 I mag.
| The far-infrared properties of the CfA galaxy sample. I - The catalog
IRAS flux densities are presented for all galaxies in the Center forAstrophysics magnitude-limited sample (mB not greater than 14.5)detected in the IRAS Faint Source Survey (FSS), a total of 1544galaxies. The detection rate in the FSS is slightly larger than in thePSC for the long-wavelength 60- and 100-micron bands, but improves by afactor of about 3 or more for the short wavelength 12- and 25-micronbands. This optically selected sample consists of galaxies which are, onaverage, much less IR-active than galaxies in IR-selected samples. Itpossesses accurate and complete redshift, morphological, and magnitudeinformation, along with observations at other wavelengths.
| An optical catalog of extragalactic emission-line objects similar to quasi-stellar objects
A catalog of 935 galaxies which have optical properties similar to thoseof QSOs is given. A subsidiary table of cross-identifications enablesthe reader to relate the name of a given object to its coordinate name.Most of the objects appear to be nonstellar. The majority, more than700, have redshifts z = 0.2 or less, and have mostly been classified asSeyfert galaxies, N systems, or radio galaxies. The Hubble diagram forall of the objects with z = 0.2 or less is shown. The redshiftdistribution peaks at z = 0.025, but there are about 200 powerful radiogalaxies in the extended tail of the distribution which have z greaterthan 0.2. There is a separate and distinct peak in the redshiftdistribution at z = 0.06.
| X-ray and infrared selected AGN. II - Optical spectroscopy
In a search for obscured active galactic nuclei, 144 X-ray/IR emittinggalaxies were selected. Optical spectroscopy of this sample ispresented. A classification according to the nuclear activity shows that28 are AGN, 39 are transition-type objects, and 44 are H II region-likegalaxies. Three of the 28 AGN are Seyfert 1 galaxies and the others areof Type 2. It is suggested that the objects identified as narrow lineAGN are obscured Seyfert 1. Most of the observed galaxies are seenedge-on, indicating that dust may have a flattened distribution coplanarto the disk of the parent galaxy. With the inclusion of the newlyidentified AGN, the sample of the X-ray emitting Seyfert 2 galaxies isfairly complete above a flux limit of log F(Hx) = -10.8.
| A survey of galaxy redshifts. IV - The data
The complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s.
| Velocity calibration of the Las Campanas redshift survey
The Center for Astrophysics redshift survey is being extended bySchectman et al. (1983) to the south galactic cap. Their initial resultsprovide independent estimates of both emission Ve velocities and theabsorption line Vc velocities, such that (Ve-Vc) = 54 + or - 13 km/s. HI line observations of 40 of the sample are presented here, to provide asecure velocity scale calibration. The Vc velocities are found to have a32 + or - 9 km/s zero-point error.
| Redshifts for 115 galaxies near the equator
New redshifts for 115 bright galaxies located near the celestial equatorare reported. The spectra were observed with a blue-sensitivephoton-counting Reticon on the 100-in. DuPont telescope, and theredshifts were derived using the data-analysis system developed for theCfA Redshift Survey. Comparisons with other measured redshifts suggestthat these data are similar in quality to the redshifts measured at Mt.Hopkins for the CfA Redshift Survey; the velocity zero point is good to10 or 15 km/s, with a typical error of 35 km/s for the individualmeasurements.
| Catalogue no.10 of nebulae discovered at the Warner observatory.
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