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Hubble Constant at Intermediate Redshift Using the CO-Line Tully-Fisher Relation
We have determined distances and Hubble ratios for galaxies atintermediate redshifts, cz ~ 10000 to 35000 km s-1, byapplying the CO-line Tully-Fisher relation to our 12CO(J=1-0)--line observations using the Nobeyama 45-m telescope, and near-IR (NIR)photometry in the J- and H-bands using the 1.88-m telescope at OkayamaAstrophysical Observatory. By averaging the Hubble ratios from the -bandresult, we obtained a Hubble constant of H0=60+/-10kms-1 Mpc-1. We argue that the CO line-NIRTully-Fisher relation can be a complimentary method to the other methodsfor measuring the distances of galaxies at intermediate and highredshifts.
| CO Observations of Luminous IR Galaxies at Intermediate Redshift
We present new measurements of the 12CO (J=1-0) emission from16 luminous infrared galaxies (LIGs) at intermediate redshift (cz ~10000-50000 km s-1). These new data were selected by isolatedand normal morphology. Although there already exist measurements of COemission from LIGs in the literature, they are mostly stronglyinteracting/merging systems. The new CO data represent an important newaddition to the literature in that they both expand the relatively smallnumber of samples of LIGs measured in CO, and they include aninteresting subset of LIGs that were selected based on isolated andnormal morphology. The CO observations were performed using the NRO 45-mtelescope. >From measurements of the CO emission and the IRASdatabase, we discuss the molecular gas and dust properties of late-typegalaxies at intermediate redshift. Comparisons of the CO and dustproperties of the new result with those from other CO measurements haverevealed the characteristics of this sample: (1) It shows the deepest COobservations of IRAS galaxies at intermediate redshift without anystrong interaction features. (2) It has typical properties of normalIRAS galaxies in terms of star-formation efficiency, color-colordiagrams and galactic nuclear activity. (3) It has a smaller gas-to-dustratio than normal IRAS galaxies. This can be explained by atwo-component dust model; our sample consists of mostly warm dust.
| Optical Spectral Signatures of Dusty Starburst Galaxies
We analyze the optical spectral properties of the complete sample ofVery Luminous Infrared Galaxies presented by Wu et al., and we find ahigh fraction (~50%) of spectra showing both a strong Hδ line inabsorption and relatively modest [O II] emission [e(a) spectra]. Thee(a) signature has been proposed as an efficient method to identifydusty starburst galaxies, and we study the star formation activity andthe nature of these galaxies, as well as the effects of dust on theirobserved properties. We examine their emission-line characteristics, inparticular their [O II]/Hα ratio, and we find this to be greatlyaffected by reddening. A search for AGN spectral signatures reveals thatthe e(a) galaxies are typically H II/LINER galaxies. We compare the starformation rates derived from the FIR luminosities with the estimatesbased on the Hα line and find that the values obtained from theoptical emission lines are a factor of 10-70 (Hα) and 20-140 ([OII]) lower than the FIR estimates (50-300 Msolaryr-1). We then study the morphological properties of the e(a)galaxies, looking for a near companion or signs of a merger/interaction.In order to explore the evolution of the e(a) population, we present anoverview of the available observations of e(a) galaxies in differentenvironments both at low and high redshift. Finally, we discuss the roleof dust in determining the e(a) spectral properties and we propose ascenario of selective obscuration in which the extinction decreases withthe stellar age.
| A statistical study of the spectra of very luminous IRAS galaxies. II. Spectral and environmental analysis
Spectroscopic observations of a sample of 73 very luminous IRAS galaxies(log(LIR/Lsun)>=11.5 for H0=50 km\s(-1) ; Mpc(-1) ,q0=0.5) from the 2 Jy redshift surveycatalogue were carried out using the 2.16 m telescope at the BeijingAstronomical Observatory. The observational data, including the opticalimages (extracted from Digital Sky Survey) and spectra for thesegalaxies, are presented in Paper I \cite[(Wu et al. 1998)]{wu98}. Inthis paper, we give the spectral and morphological classifications forthese very luminous IRAS galaxies (VLIRGs). We show that about 60% ofVLIRGs exhibit AGN-like spectra (Seyfert 1s, Seyfert 2s, LINER-likegalaxies). This fraction goes up to 82% for the ultraluminous IRASgalaxies (ULIRGs) subsample (Log(LIR/Lsun) >=12.0). 56% of the VLIRGs show strong interaction or merging signatures;this fraction rises to 91% for the ULIRGs. These statistical resultsstrongly suggest that interaction triggers nuclear activities andenhances the infrared luminosity. We find that LINER and a mixture typewhich have optical properties of both HII galaxies and LINERs could beat the transition stage from infrared luminous HII galaxies to AGNs;their main energy production is from starbursts as well as AGNs. Bothinfrared luminosities and Hα equivalent widths increasedramatically as nuclear separations between VLIRGs and their nearestneighbors decrease. There is little doubt that strong starbursts happenin the nuclei of VLIRGs. Assuming class 0 as advanced merger, weconstruct a simple merger sequence, from morphological classes 1 to 4(with near or far companions), to class 5 and 6 (interacting pairs andmergers) and then to class 0 (isolated galaxies). Along this sequence,VLIRGs evolve from HII galaxies to AGNs. Table 1 is only available atthe CDS via anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr
| A statistical study of the spectra of very luminous IRAS galaxies. I. Data
This paper presents the results of spectral observations for the largestcomplete sample of very luminous IRAS galaxies obtained to date. Thesample consists of those 73 objects for which log(L_IR/Lsun)>= 11.5 (H0=50;km; s(-1) Mpc(-1) , q0=0.5) andmag <= 15.5 , and was extracted from the 2 Jy IRAS redshift catalog.All the spectra were obtained using the 2.16 m telescope of BeijingAstronomical Observatory during the years 1994-1996. A total of 123galaxy spectra were obtained with spectral ranges of 4400;Angstroms to7100;Angstroms and 3500;Angstroms to 8100;Angstroms at resolutions of11.2;Angstroms and 9.3;Angstroms respectively. In addition to the 73spectra for sample galaxies, we also present spectra for ten non-samplegalaxies and a further 40 for the companions of sample galaxies. Thedata presented include nuclear spectrum and the parameters describingthe emission lines, absorption lines and continua as well as DSS imagesand environmental parameters. Table 1 is also available in electricform, Table 2-4 are only available in electronic form form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130. 79.128.5) or via http:cdsweb.u-strasbg.fr/Abstract.html. Figures 4 and 9 are published in theon-line version of A&A..
| Distance Measurement of Galaxies to a Redshift of ~ 0.1 Using the CO-Line Tully-Fisher Relation
We report on the first results of a long-term project to derive thedistances of galaxies at cosmological distances by applying the CO-linewidth--luminosity relation. We have obtained deep CO-line observationsof galaxies at redshifts of up to cz ~ 29000 km s(-1) using the Nobeyama45-m mm-wave telescope; also, some supplementary data were obtainedusing the IRAM 30-m telescope. We have detected CO-line emission fromseveral galaxies, and used their CO-line widths to estimate the absoluteluminosities based on the line-width--luminosity relation. In order toobtain photometric data and an inclination correction, we also performedoptical imaging observations of the CO-detected galaxies using the CFHT3.6-m telescope at high resolution. The radio and optical data have beencombined to derive the distance moduli and distances of the galaxies;also, the Hubble ratios were estimated for these galaxies. We proposethat the CO-line width--luminosity relation can be a powerful method toderive the distances of galaxies to redfhifts of z ~ 0.1, and to derivethe Hubble ratio within a significant volume of the universe.
| 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.
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