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Measuring shapes of galaxy images - II. Morphology of 2MASS galaxies
We study a sample of 112 galaxies of various Hubble types imaged in theTwo Micron All Sky Survey (2MASS) in the near-infrared (NIR; 1-2 μm)J, H and Ks bands. The sample contains (optically classified)32 ellipticals, 16 lenticulars and 64 spirals acquired from the 2MASSExtended Source Catalogue (XSC).We use a set of non-parametric shape measures constructed from theMinkowski functionals (MFs) for galaxy shape analysis. We useellipticity (ɛ) and orientation angle (Φ) as shapediagnostics. With these parameters as functions of area within theisophotal contour, we note that the NIR elliptical galaxies withɛ > 0.2 show a trend of being centrally spherical andincreasingly flattened towards the edge, a trend similar to images inoptical wavelengths. The highly flattened elliptical galaxies showstrong change in ellipticity between the centre and the edge. Thelenticular galaxies show morphological properties resembling eitherellipticals or disc galaxies. Our analysis shows that almost half of thespiral galaxies appear to have bar-like features while the rest arelikely to be non-barred. Our results also indicate that almost one-thirdof spiral galaxies have optically hidden bars.The isophotal twist noted in the orientations of elliptical galaxiesdecreases with the flattening of these galaxies, indicating that twistand flattening are also anticorrelated in the NIR, as found in opticalwavelengths. The orientations of NIR lenticular and spiral galaxies showa wide range of twists.
| The 2dF Galaxy Redshift Survey: the population of nearby radio galaxies at the 1-mJy level
We use redshift determinations and spectral analysis of galaxies in the2dF Galaxy Redshift Survey to study the properties of local radiosources with S>=1mJy. 557 objects (hereafter called the spectroscopicsample) drawn from the FIRST survey, corresponding to 2.3 per cent ofthe total radio sample, are found in the 2dFGRS catalogue within thearea9h48m<~RA(2000)<~14h32m and -2.77°<~Dec.(2000)<~2.25°, down to a magnitudelimit bJ=19.45. The excellent quality of 2dF spectra allowsus to divide these sources into classes, according to their opticalspectra. Absorption-line systems make up 63 per cent of thespectroscopic sample. These may or may not show emission lines due toAGN activity, and correspond to `classical' radio galaxies belongingmainly to the FRI class. They are characterized by relatively highradio-to-optical ratios, red colours, and high radio luminosities(1021<~P1.4GHz/WHz-1sr-1<~1024). Actively star-forming galaxies contributeabout 32 per cent of the sample. These objects are mainly found at lowredshifts (z<~0.1) and show low radio-to-optical ratios, blue coloursand low radio luminosities. We also found 18 Seyfert 2 galaxies (3 percent) and four Seyfert 1s (1 per cent). Analysis of the local radioluminosity function (LF) shows that radio galaxies are well described bymodels that assume pure luminosity evolution, at least down to radiopowersP1.4GHz<~1020.5WHz-1sr-1.Late-type galaxies, whose relative contribution to the radio LF is foundto be lower than was predicted by previous works, present an LF which iscomparable with the IRAS galaxy LF. This class of sources thereforeplausibly constitutes the radio counterpart of the dusty spirals andstarbursts that dominate the counts at 60μm.
| 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.
| The structure of spiral galaxies - II. Near-infrared properties of spiral arms
We have imaged a sample of 45 face-on spiral galaxies in the K band, todetermine the morphology of the old stellar population, which dominatesthe mass in the disc. The K-band images of the spiral galaxies have beenused to calculate different characteristics of the underlying densityperturbation such as arm strengths, profiles and cross-sections, andspiral pitch angles. Contrary to expectations, no correlation was foundbetween arm pitch angle and Hubble type, and combined with previousresults this leads us to conclude that the morphology of the old stellarpopulation bears little resemblance to the optical morphology used toclassify galaxies. The arm properties of our galaxies seem inconsistentwith predictions from the simplest density wave theories, and someobservations, such as variations in pitch angle within galaxies, seemhard to reconcile even with more complex modal theories. Bars have nodetectable effect on arm strengths for the present sample. We have alsoobtained B-band images of three of the galaxies. For these galaxies wehave measured arm cross-sections and strengths, to investigate theeffects of disc density perturbations on star formation in spiral discs.We find that B-band arms lead K-band arms and are narrower than K-bandarms, apparently supporting predictions made by the large-scale shockscenario, although the effects of dust on B-band images may contributetowards these results.
| The structure of spiral galaxies - I. Near-infrared properties of bulges, discs and bars
We present data for a sample of 45 spiral galaxies over a range ofHubble types, imaged in the near-IR JK bands. Parameters are calculateddescribing the bulge, disc and bar K-band light distributions, and welook for correlations showing the interrelation between thesecomponents. We find that bulge profiles are not well-fitted by theclassic de Vaucouleurs profile, and that exponential or R^1/2 fits arepreferred. The bulge-to-disc ratio correlates only weakly with Hubbletype. Many of the galaxies show central reddening of their J-K colours,which we interpret as due to nuclear starbursts or dusty AGN. We definea new method for measuring the strength of bars, which we call`equivalent angle'. We stress that this is better than the traditionalbar-interbar contrast, as it is not subject to seeing and resolutioneffects. Bars are found in 40 of the 45 galaxies, nine of which had beenpreviously classified as unbarred. Bar strengths are found not tocorrelate with disc surface brightness or the presence of nearneighbours, but a tendency is found for the most strongly barredgalaxies to lie within a restricted, intermediate range of bulge-to-discratio. Bar light profiles are found to be either flat or exponentiallydecreasing along their long axes, with profile type not correlatingstrongly with Hubble type. Bar short axis profiles are significantlyasymmetric, with the steeper profile being generally on the leadingedge, assuming trailing arms. In the K band we find bars with higheraxial ratios than have been found previously in optical studies.
| 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.
| 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.
| Kinematics and dynamics of the MKW/AWM poor clusters
We report 472 new redshifts for 416 galaxies in the regions of the 23poor clusters of galaxies originally identified by Morgan, Kayser, andWhite (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poorclusters now have 10 or more available redshifts within 1.5/h Mpc of thecentral galaxy; 11 clusters have at least 20 available redshifts. Basedon the 21 clusters for which we have sufficient velocity information,the median velocity scale is 336 km/s, a factor of 2 smaller than foundfor rich clusters. Several of the poor clusters exhibit complex velocitydistributions due to the presence of nearby clumps of galaxies. We checkon the velocity of the dominant galaxy in each poor cluster relative tothe remaining cluster members. Significantly high relative velocities ofthe dominant galaxy are found in only 4 of 21 poor clusters, 3 of whichwe suspect are due to contamination of the parent velocity distribution.Several statistical tests indicate that the D/cD galaxies are at thekinematic centers of the parent poor cluster velocity distributions.Mass-to-light ratios for 13 of the 15 poor clusters for which we havethe required data are in the range 50 less than or = M/LB(0)less than or = 200 solar mass/solar luminosity. The complex nature ofthe regions surrounding many of the poor clusters suggests that thesegroupings may represent an early epoch of cluster formation. Forexample, the poor clusters MKW7 and MKWS are shown to be gravitationallybound and likely to merge to form a richer cluster within the nextseveral Gyrs. Eight of the nine other poor clusters for which simpletwo-body dynamical models can be carried out are consistent with beingbound to other clumps in their vicinity. Additional complex systems withmore than two gravitationally bound clumps are observed among the poorclusters.
| Redshift observations in the Hydra-Centaurus region
The paper reports 406 redshifts for galaxies in the northern galactichemisphere, south of delta = 0 deg. A substantial fraction of theobserved galaxies are located in the equatorial zone between deltavalues of -17.5 and 0 deg. By combining these new data with thoseavailable in the literature, it is possible to extend the original CfAredshift survey of galaxies brighter than m(B(0)) = 14.5 to b = 30 deg,south of delta = 0. New data taken at lower galactic latitudes alsocontribute to the existing surveys of the Hydra-Centaurus complex.
| A spectrophotometric catalogue of HII galaxies
A spectrophotometric catalog is presented of 425 emission-line galaxiesdiscovered in objective prism surveys for which redshifts, emission-lineintensities, equivalent widths, and absolute fluxes are derived. Thevast majority of objects in the catalog are H II region-like galaxies (HII galaxies). In more than 80 H II galaxies the forbidden line O III4363 was measured with accuracy good enough to permit precise electrontemperature determinations. The observational parameters that define theproperties of H II galaxies as a class are characterized and discussed.
| Observations of a Complete Sample of Emission-Line Galaxies. II. Properties of the UM Survey Galaxies
We utilize our extensive collection of imaging and spectroscopic data toinvestigate the properties of the emission-line galaxies (ELGs) found inLists IV and V of the University of Michigan (UM) objective-prismsurvey. The majority of the ELGs in this deep sample have apparentmagnitudes in the range 16.0 < m_B_ < 19.0. the distribution of B- V colors is nearly identical with that for the Markarian galaxies,indicating that the line-selection technique employed is very efficientat finding the same kinds of activity as found in UV-excess surveys.However, the UM sample differs markedly from complete magnitude-limitedsamples of galaxies in that it contains a very high proportion oflow-luminosity galaxies. The median luminosity is M_B_ = - 18.1, and 25%of the UM galaxies have M_B_ > -16.5. The vast majority are dwarfs,with diameters less than 10 kpc. Each ELG is classified into one of 10natural groups of active galaxies. Seyfert galaxies make up 11% of theentire sample, a result nearly identical with that for the Markariansurvey. The ELG types most commouly found are intermediate- tolow-luminosity objects with irregular or unresolved morphologies and avery intense star-formation region which dominates the optical output ofthe galaxy. Emission-line ratio diagnostic diagrams reveal that the ELGsin the different natural groups tend to have distinctly different lineratios. This suggests that the various ELG types differ from one anotherin terms of the metal abundance of their ionized gas, and we derive aluminosity-metallicity relationship which is singular to those foundpreviously for disk and irregular galaxies.
| Observations of a complete sample of emission-line galaxies. I - CCD imaging and spectroscopy of galaxies in UM lists IV and V. II - Properties of the UM survey galaxies
CCD imaging and spectroscopic observations of emission-line galaxycandidates from lists IV and V of the University of Michiganobjective-prism survey are used to study the properties of the surveyconstituents and the selection characteristics and completeness limitsof the survey. The total magnitudes, B-V colors, apparent diameters, andmorphoplocial and environmental characteristics of 166 objects arepresented. It is found that 95 percent of the objects for which thereare sufficient data exhibit emission lines. Also, contour diagrams ofthe CCD images and plots of the spectra of several galaxies arepresented.
| The far-infrared properties of optically selected emission-line galaxies
A high-sensitivity sample of IRAS-detected emission-line galaxies (ELGs)is used to investigate the FIR properties of these galaxies and therelative selection biases of the UM Curtis Schmidt and IRAS surveys.Color-color diagrams indicate that the FIR emission from the UM ELGs isdue primarily to warm dust heated directly by the active star-formingregions that are responsible for the strong optical emission lines. TheFIR luminosity of the UM ELGs is found to correlate with both H-beta andblue luminosities, suggesting that the current star-formation rate inthese objects is more closely coupled to the past star-formation historythan is generally acknowledged.
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