내용
사진
사진 업로드
DSS Images Other Images
관련 글
A search for Low Surface Brightness galaxies in the near-infrared. I. Selection of the sample
A sample of about 3800 Low Surface Brightness (LSB) galaxies wasselected using the all-sky near-infrared (J, H and Ks-band)2MASS survey. The selected objects have a mean central surfacebrightness within a 5'' radius around their centre fainter than 18 magarcsec-2 in the Ks band, making them the lowestsurface brightness galaxies detected by 2MASS. A description is given ofthe relevant properties of the 2MASS survey and the LSB galaxy selectionprocedure, as well as of basic photometric properties of the selectedobjects. The latter properties are compared to those of other samples ofgalaxies, of both LSBs and ``classical'' high surface brightness (HSB)objects, which were selected in the optical. The 2MASS LSBs have aBT_c-KT colour which is on average 0.9 mag bluerthan that of HSBs from the NGC. The 2MASS sample does not appear tocontain a significant population of red objects.All tables and Figs. 2a-c are only available in electronic form athttp://www.edpsciences.org
| Properties of Spiral-Peculiar Type of Kiso Ultraviolet-Excess Galaxies
We investigated the optical spectroscopic properties of 44KisoUltraviolet-excess Galaxies (KUG), which is one of the most well-knowncatalogs of blue galaxies. All of our sample galaxies belong to thespiral-peculiar (Sp) type, the morphological class of spiral galaxy witha peculiar bar and/or a nucleus in KUGs. Since the Sp type is consideredto be the most peculiar group among KUGs, and about 45% of the KUGs havethe Sp type, a detailed study of the Sp type is crucial to understandthe characteristics of the KUG. The sample galaxies have luminosities inthe B-band of about 108 to less than 1010 in solarunit, and a median physical size of 13kpc. From the nuclear spectra, wedetermined line excitation sources in 39 galaxies. Among them, wedetected four AGNs reliably: two Seyfert1s, one Seyfert2, and one LINER.Other sample galaxies show moderately star-forming activity. For thiscategory of ordinary KUG group, the mode of the Hα equivalentwidth at the nuclear region is a bin of 40 to 60Å. Three galaxieshave extreme starburst nuclei with an Hα equivalent width of morethan 200Å. The internal extinction of AV is about0.8mag, which suggests that the star-forming nuclei are not heavilyenshrouded by dust.
| 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.
| On the Influence of the Environment on the Star Formation Rates of a Sample of Galaxies in Nearby Compact Groups
We present the results of a study of the star formation rates (SFRs) ofa sample of disk galaxies in nearby compact groups compared with theSFRs of a sample of field galaxies. For this purpose, Hαluminosities and equivalent widths were derived for the galaxies of oursample. A direct comparison of the equivalent widths and Hαluminosities, normalized to the B luminosities and estimated area of thegalaxies of both samples, yields the result that the median values ofthese quantities are almost identical for both samples, although thedistributions for the compact-group sample are broader around the meanvalue than was found in the field galaxy sample. This result can beexplained by assuming that although interactions between galaxies incompact groups can alter the SFRs, the median value of the normalizedSFRs is preserved, being almost indistinguishable from the correspondingvalue for field galaxies. Measuring the global L_Hα/L_B of thegroups, including early-type galaxies, we find that most of the groupsthat show the highest level of L_Hα/L_B with respect to a set ofsynthetic groups built out of field galaxies show tidal features in atleast one of their members. Finally, we have explored the relationshipbetween the ratio L_Hα/L_B and several relevant dynamicalparameters of the groups: velocity dispersion, crossing time, radius,and the mass-to-luminosity ratio, finding no clear correlation. Thissuggests that the exact dynamical state of a group does not control theSFR of the group as a whole. Our results are compatible with a scenariofor compact groups of galaxies in which the dark matter of the group isarranged in a common halo, therefore preventing a fast collapse of thegalaxies.
| Disk Galaxies in the Outer Local Supercluster: Optical CCD Surface Photometry and Distribution of Galaxy Disk Parameters
We report new B-band CCD surface photometry on a sample of 76 diskgalaxies brighter than B_T = 14.5 mag in the Uppsala General Catalogueof Galaxies that are confined within a volume located in the outer partof the Local Supercluster. With our earlier published I-band CCD andhigh signal-to-noise ratio 21 cm H I data, this paper completes ouroptical surface photometry campaign on this galaxy sample. As anapplication of this data set, the B-band photometry is used here toillustrate two selection effects that have been somewhat overlooked inthe literature but that may be important in deriving the distributionfunction of disk central surface brightness (CSB) of disk galaxies froma diameter- and/or flux-limited sample: a Malmquist-type bias againstdisk galaxies with small disk scale lengths (DSLs) at a given CSB and adisk inclination-dependent selection effect that may, for example, biastoward inclined disks near the threshold of a diameter-limited selectionif disks are not completely opaque in the optical. Taking intoconsideration these selection effects, we present a method ofconstructing a volume-sampling function and a way to interpret thederived distribution function of CSB and DSL. Application of this methodto our galaxy sample implies that if galaxy disks are optically thin,CSB and DSL may well be correlated in the sense that, up to aninclination-corrected limiting CSB of about 24.5 mag arcsec^-2 that isadequately probed by our galaxy sample, the DSL distribution of galaxieswith a lower CSB may have a longer tail toward large values unless thedistribution of disk galaxies as a function of CSB rises rapidly towardfaint values.
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| Influence of a partial incompleteness of the sample on the determination of the Hubble constant.
This paper presents a study of the Malmquist bias effect in thedetermination of the Hubble constant from the method of "sosies"(look-alike) galaxies. It is shown that a bias appears when a partialincompleteness exists in the sample. A new method, based on the use ofthe completeness curve, is proposed to correct for such a bias. Afterthis correction, the Hubble constant drops of about 20% just because ofthe existence of the partial incompleteness. From the present resultsand on the acceptance of the distance modulus of primary calibrators,the value of the Hubble constant would be: H_0_=~60km/s/Mpc with aninternal statistical error of about 2km/s/Mpc.
| On the question of radio emission of spiral galaxies in groups of galaxies
It has been shown that the radio emission properties of spiral galaxies,if the other conditions are the same, are determined rather by thepresence of the close neighbours than by space density of galaxiesaround them. The rate of occurence of radio sources and their radioluminosities among the spiral members of groups of galaxies depend onthe projected seperation between them and their nearest neighbour. Theshorter this seperation the higher the probability of radio emission.
| 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.
| Measuring the Hubble constant and our Virgo-infall velocity independently
A sample of spiral galaxies with BT less than 14.5 located intwo local volumes, one in the direction of, but behind, the VirgoCluster (behind-Virgo volume (BV)) and the other in the oppositedirection (anti-Virgo volume (AV)), were used via a Tully-Fisher (TF)relation to derive the following two parameters: HAB, themean Hubble ratio between AV and BV, and delta vparallel, thepeculiar velocity of the Local Group in the direction of the VirgoCluster (VC) with respect to a uniformly expanding reference systemdefined by our AV and BV sub-samples. The two sampled volumes, separatedby a velocity interval of 5600 km/s, form an antipodal pair. Thisparticular geometry not only allows us to derive the two parametersindependently but also reduces the dynamical effect of the LocalSupercluster on HAB without increasing the Malmquist bias. Bylimiting our sample to spiral galaxies having large velocity widthsWR, we effectively reduce the TF scatter and Malmquist biasin our sample. The TF zero point and dispersion were then determined byfurther correcting for the small residual Malmquist bias. An additionalsample of fainter galaxies was used to test for a non-Gaussian tail tothe TF disperison. We found no evidence for such a tail and formallygive an upper limit of about 18% for the fractional contribution of anunseen tail. The average intrinsic TF dispersion for the dominantGaussian component is sigmaTF0 approximately 0.33mag for WR approximately equal to or greater than 180 km/s.Our numerical results are delta vparallel approximatelyequals 414 +/- 82 km/s and HAB approximately equals (84.0 +/-2.4)(1 + epsilon) km/s Mpc, where (1 + epsilon) accounts for anysystematic error between the calibrators and the sample galaxies.Various dynamical models were tested to explore the effect onHAB of the uncertainties in the local velocity field.Constrained by our observed delta vparallel as well as otherobservational quantities, we found that the rms deviation from unity ofHAB/H0 (where H0 is the Hubble constantfor each model) is 5%, making HAB a good indicator forH0. Taking this variation as an additional error, our formalestimate for the Hubble constant is H0 approximately equals(84 +/- 5)(1 + epsilon) km/s Mpc.
| CO observations of several amorphous and Magellanic irregular galaxies
We report upper limits on the (C-12)O J = 1 - 0 and 2 - 1 line emissionfor several positions in five Magellanic irregular and amorphousgalaxies. The positions in three of the galaxies were chosen becausethey were peaks in H I interferometer maps. The galactic centers wereobserved for the other two. The upper limits on the emission are below(sometimes far below) what was expected based upon the empiricalrelationship between CO and IRAS 100-micron flux, suggesting that one ormore of the following is (are) true: (1) much of the molecular gas hasbeen used up during the star formation process, (2) the H2 has beendissociated by the intense UV radiation produced by the massive stars,(3) that the CO emitting surfaces of the molecular clouds are smallerdue to the effects of dissociation of the intense UV radiation, or (4)that CO is not tracing the H2. These results, when combined with otherwork, suggest that molecular gas is a relatively transient phenomenon indwarf galaxies, unlike spirals.
| H I 21 centimeter observations and I-band CCD surface photometry of spiral galaxies behind the Virgo Cluster and toward its antipode
Sample selection, radio and optical data acquisition and reduction, andobservation results are presented for spiral galaxies behind the VirgoCluster and toward its antipode. I-band CCD photometry was obtained forall the bright galaxies and part of the sample of faint galaxies in thetwo local volumes was studied. The statistical properties of the galaxysamples are discussed.
| A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
| 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.
| KISO survey for ultraviolet-excess galaxies. XIII.
Not Available
| A self-regulated star formation rate as a function of global galactic parameters
A sample of active dwarf galaxies and a sample of Sc and irregulargalaxies are analyzed based on the assumption that the stellar formationrate is self-regulated in such a way that it maintains the criticalpressure P(max) near the gas pressure P(g) of the interstellar medium,where P(max) is the pressure of the marginal state of stability for thetransition warm gas to small clouds. The stellar formation rate Psi(PP)consistent with the condition P(max) = P(g), can be expressed as asimple analytical function of global galactic parameters. When it isassumed that the dust temperature, the gas metallicity, and the galacticdiameter remain constant, it is found that Psi(PP) is reduced to the lawof Schmidt with an exponent value of 1.43. Specifically, for the Galaxy,it is fond that Psi(PP) = about 10 solar masses/yr, which is reasonablyconsistent with previous values.
| IRAS observations of a large sample of normal irregular galaxies
IRAS 12, 25, 60, and 100 micron data are presented for a sample of Irrgalaxies which span a large range in star-formation activity. It isfound that the dwarf, giant, and amorphous Irr's generally have similarIR properties. The typical L(IR)/L(H-alpha) ratios of most classes ofIrr's, except for many of the luminous blue galaxies, are low comparedwith those of spiral galaxies and are consistent with the Irr's beingrelatively transparent systems without large amounts of optically hiddenstar formation. Compared with spiral galaxies, the Irr's have similarL(IR)/L(B) ratios, warmer S(100)/S(60) ratios, cooler S(25)/S(12)ratios, and lower dust-to-H I gas mass ratios. The temperature,dust-to-H I gas mass ratios, and L(IR)/L(B) ratios do not correlate withthe metallicity of the ionized gas of the Irr's. A correlation betweenthe IR fluxes and both the H-alpha and the blue stellar fluxes is foundfor the Irr's.
| Star-formation rates and forbidden O II emission in blue galaxies
Observations of forbidden O II 3727 A and H-beta emission-line strengthsare presented from large-aperture spectrophotometric observations ofnearby (z less than 0.1) optically blue galaxies covering a wide rangein surface brightness and luminosity. The forbidden O II emission-lineequivalent widths in these galaxies primarily lie between 30 and 100 A.Emission-line strengths in nearby blue galaxies thus resemble thosefound in faint galaxies at moderate-to-high redshifts. The most activelystar-forming nearby galaxies are characterized by surface brightness inthe forbidden O II line of about 10 to the -15th to 10 to the -14thergs/s per sq cm per sq arcsec over spatial distances of more than 1kpc. The fluxes of the forbidden O II and H-beta emission lines are wellcorrelated, and thus forbidden O II luminosities can be used to deriveapproximate star-formation rates in blue galaxies.
| Stellar populations and star formation in irregular galaxies
A review and intercomparison is conducted of data on variousmorphologically-chosen groups of irregular galaxies in order tounderstand the underlying physical mechanisms that differentiate thesesystems. Particular attention is given to the observational clues to thestellar content, star-formation processes, and star-formation historiesof these galaxies, with an emphasis on the uncertainties and the manyunanswered questions.
| Star formation in active dwarf galaxies
Star formation and the ISM in active dwarf galaxies are studied based ondata from the IRAS Point Source Catalog. The dwarf galaxies that showevidence of recent energetic star formation are generally also strongfar-infrared emitters; thus, active current star formation is associatedwith a history of energetic star formation. A fraction of the galaxiesconsidered here have a star formation rate that is significantly greaterthan the average rate in the recent past. Available gas is beingconsumed as efficiently in the presently active dwarfs as in the MilkyWay. A primary difference between galaxies that are energeticallyforming stars and those that are not is the difference in gas mass, aswell as the efficiency of star formation. The most important process maybe the assembly of large amounts of gaseous material.
| Empirical properties of nearby groups of galaxies
A new list of nearby groups was composed by Vennik (1984) on the basisof radial velocity data of galaxies using the hierarchical clusteringtechnique described by Materne (1978) and Tully (1980). This paperpresents a detailed analysis of empirical properties of groups on thebasis of that list. Various group selection criteria are compared, andthe main parameters of individual groups, possible selection effects,and relationships between various properties of the groups arediscussed. Synthesized groups are composed based on the luminosities ofthe groups and the dominating morphology.
| Arecibo H I data for 136 spiral galaxies
The results of observations of the neutral hydrogen emission of 136spiral galaxies observed using the 21 cm spectral-line system of theArecibo Observatory are presented. Most of the 114 detected objects havebeen mapped along the major axis, and cumulative spectra andposition-velocity contour maps for each of them are presented. The dataare used to determine the overall H I content, systemic velocity, linewidths, and scale-length H I diameters. Data are also presented, indetailed tabular form, for each of the positions observed on thedetected objects.
| Infrared colors of blue irregular galaxies
JHK photometry are presented for a sample of blue irregular galaxies,including nearby giant systems and more distant luminous compactgalaxies. Four giant H II regions were also observed for comparison. TheH II regions exhibit a considerable range in JHK and V-K colors, whichare attributed to variations in the massive blue and red stellarpopulations and in the amount of dust. The irregular galaxies, on theother hand, have rather homogeneous colors which are similar to those ofspiral and elliptical galaxies. From the infrared colors alone, it wasnot possible to distinguish between giant stars, asymptotic giants, andsupergiants as the dominant source of infrared light in irregulars.However, the uniformity of JHK colors from galaxy to galaxy as comparedwith individual young stellar systems suggests that young populationsare not major contributors to the infrared light. Also, no correlationwas found between metallicity and infrared colors in irregular galaxies.
| A search for environmental effects on the optical properties of galaxies in groups
Environmental density-related modifications of basic optical properties(luminosities, sizes, axial ratios, and colors) of galaxies belonging toGeller and Huchra's (1983) groups have been investigated. Remarkably, itis found that the broad maxima of the distributions of luminosities anddiameters of spirals and the whole corresponding distributions oflenticulars tend to move to lower values as one goes to groups of highcompactness, whereas the luminosity-diameter relationship of spiralstends to become flatter. No color and axial ratio differences betweengalaxies of high- and low-compactness groups have been detected.
| Star formation histories of irregular galaxies
The star formation histories of a selection of irregular and spiralgalaxies are analyzed using three parameters for sampling the starformation rate in different epochs: galaxy mass; blue luminosity; andLyman continuum photon fluxes derived from Hz luminosities. It is foundthat for most irregular galaxies these parameters are consistent with anearly constant SFR and a Salpeter initial mass function over thelifetimes of the galaxies. The spiral and high-mass irregular galaxiesappear to have had a constant SFR over the past few billion years butalso have high total mass indicating either an early phase of intensestar formation or the presence of dark matter. Global bursts of starformation among irregular galaxies appear to be rare. The constant SFRhistory implies that the simple classical model in which star formationis proportional to gas density in a closed system cannot be correct forirregular galaxies. Some alternative models for constant global SFRs arediscussed.
| 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.
| Dust in backlit galaxies - Properties of the foreground systems in NGC 3314 and NGC 1275
New digital imaging of NGC 3314 and NGC 1275 is presented. NGC 3314consists of an Sc galaxy in front of an Sb; BVRI data are used toestimate the extinction through and between spiral arms and derive R =3.5 for the extinction curve, with large uncertainties due to structurein the foreground galaxy. Dust lanes are identified in NGC 1275, ofoptical depth similar to those in NGC 3314, and occurring in associationwith giant H II regions; these imply a type Sc or Scd for the foregroundobject. This object lies outside the low-velocity filament system and isprobably not interacting with the main body of NGC 1275.
| Global properties of irregular galaxies
Optical and radio observations of global properties are presented for asample of noninteracting irregular galaxies and some companion objects.The data consist of intermediate-band filter photometry, large aperturespectrophotometry, small aperture spectrophotometry of individual H IIregions, and H I 21 cm telescope observations. The galaxies are found tobe generally blue, and may not show the classical two-peaked H I 21 cmprofile. There is no correlation between the SFR and global gas orabundance parameters, which implies that local, rather than globalcharacteristics govern the star formation process. Metallicities aregenerally low, comparable to the Magellanic Clouds, and there areabsorption features characteristic of cool stars in the spectraregardless of the strength of the SFR in the observed region.Observations appear to agree best with the gas infall model.
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
INHABITED SKY
