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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.
|Studies of Extragalactic Formaldehyde and Radio Recombination Lines|
We present the most sensitive and extensive survey yet performed ofextragalactic H2CO 6 cm (4.829 GHz) emission/absorption.Sixty-two sources were observed with the C-band system of the AreciboTelescope to a 1 σ rms noise level of ~0.3 mJy. We report a newdetection of H2CO 6 cm absorption toward NGC 520 and theconfirmation of H2CO 6 cm absorption toward several sources.We report confirmation of H2CO 6 cm emission toward the OHmegamasers Arp 220, IC 860, and IRAS 15107+0724. At present these arethe only extragalactic H2CO 6 cm emitters independentlyconfirmed. A characterization of the properties of formaldehydeabsorbers and emitters based on infrared properties of the galaxies isdiscussed. We also conducted a simultaneous survey of the H110αhydrogen recombination line toward a sample of 53 objects. We report thedetection of H110α toward the giant extragalactic H II region NGC604 in M33.
|An IRAS High Resolution Image Restoration (HIRES) Atlas of All Interacting Galaxies in the IRAS Revised Bright Galaxy Sample|
The importance of far-infrared observations for our understanding ofextreme activity in interacting and merging galaxies has beenillustrated by many studies. Even though two decades have passed sinceits launch, the most complete all-sky survey to date from which far-IRselected galaxy samples can be chosen is still that of the InfraredAstronomical Satellite (IRAS). However, the spatial resolution of theIRAS all-sky survey is insufficient to resolve the emission fromindividual galaxies in most interacting galaxy pairs, and hence previousstudies of their far-IR properties have had to concentrate either onglobal system properties or on the properties of very widely separatedand weakly interacting pairs. Using the HIRES image reconstructiontechnique, it is possible to achieve a spatial resolution ranging from30" to 1.5m (depending on wavelength and detector coverage), whichis a fourfold improvement over the normal resolution of IRAS. This issufficient to resolve the far-IR emission from the individual galaxiesin many interacting systems detected by IRAS, which is very importantfor meaningful comparisons with single, isolated galaxies. We presenthigh-resolution 12, 25, 60, and 100 μm images of 106 interactinggalaxy systems contained in the IRAS Revised Bright Galaxy Sample (RBGS,Sanders et al.), a complete sample of all galaxies having a 60 μmflux density greater than 5.24 Jy. These systems were selected to haveat least two distinguishable galaxies separated by less than threeaverage galactic diameters, and thus we have excluded very widelyseparated systems and very advanced mergers. Additionally, some systemshave been included that are more than three galactic diameters apart,yet have separations less than 4' and are thus likely to suffer fromconfusion in the RBGS. The new complete survey has the same propertiesas the prototype survey of Surace et al. We find no increased tendencyfor infrared-bright galaxies to be associated with other infrared-brightgalaxies among the widely separated pairs studied here. We find smallenhancements in far-IR activity in multiple galaxy systems relative toRBGS noninteracting galaxies with the same blue luminosity distribution.We also find no differences in infrared activity (as measured byinfrared color and luminosity) between late- and early-type spiralgalaxies.
|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.
|Large-Scale Structure at Low Galactic Latitude|
We have extended the CfA Redshift Survey to low galactic latitudes toinvestigate the relation between the Great Wall in the North GalacticCap and the Perseus-Pisces chain in the South Galactic Cap. We presentredshifts for 2020 galaxies in the Catalogue of Galaxies and of Clustersof Galaxies (Zwicky et al. 1961-68, CGCG) in the following regions: 4^h^<= α <= 8^h^, 17^h^ <= α <= 20^h^, 0^deg^ <=δ <= 45^deg^. In these regions, the redshift catalogue includes1664 galaxies with B(0) <= 15.5 (of which 820 are newly measured) andis 97% complete. We also include redshifts for an additional 356galaxies in these regions with B(O) > 15.5; of these, 148 werepreviously unmeasured. The CGCG samples the galaxy distribution down tob_II_ = 10^deg^. In this paper, we discuss the acquisition and reductionof the spectra, and we examine the qualitative features of the redshiftdistribution. The Great Wall and the Perseus-Pisces chain are not simplyconnected across the Zone of Avoidance. These structures, which at firstappear to be coherent on scales of ~100 h^-1^ Mpc or more, actually formthe boundaries of neighboring voids of considerably smaller scale,approximately 50h^-1^ Mpc. The structures delineated by ouroptically-selected sample are qualitatively similar to those detected bythe far-infrared-selected IRAS 1.2 Jansky Survey (Fisher et al. 1995).Although the IRAS survey probes more deeply into the Zone of Avoidance,our optically-selected survey provides better sampling of structures atb_II_ >= 10^deg^.
|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.
|Identifying galaxies in the zone of avoidance|
A set of IR color criteria was applied to sources in the IRAS PointSource Catalog at low Galactic latitudes in order to select candidategalaxies. A total of 371 of the selected sources within a Galacticlatitude range (b) = 2-16 deg were searched for H I with the Arecibo 305m radio telescope. Twenty-six percent (97) were detected, including 36galaxies previously known only as IRAS sources. The H I spectra of thedetected galaxies are presented together with their observed redshiftsand velocity widths.
|A study of the large-scale structure in the distribution of galaxies in a region centered about the Cancer cluster. I - Initial observational results. II - Further observational results|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986AJ.....91..705B&db_key=AST
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