Classifications of the Host Galaxies of Supernovae, Set II

Classifications on the DDO system are given for an additional 231 host galaxies of supernovae that have been discovered during the course of the Lick Observatory Supernova Search with the Katzman Automatic Imaging Telescope (KAIT). This brings the total number of hosts of supernovae discovered (or independently rediscovered) by KAIT, which have so far been classified on a homogeneous system, to 408. The probability that SNe Ia and SNe II have a different distribution of host galaxy Hubble types is found to be 99.7%. A significant difference is also found between the distributions of the host galaxies of SNe Ia and of SNe Ibc (defined here to include SNe Ib, Ib/c, and Ic). However, no significant difference is detected between the frequency distributions of the host galaxies of SNe II and SNe IIn. This suggests that SNe IIn are generally not SNe Ia embedded in circumstellar material that are masquerading as SNe II. Furthermore, no significant difference is found between the distribution of the Hubble types of the hosts of SNe Ibc and of SNe II. Additionally, SNe II-P and SNe II-L are found to occur among similar stellar populations. The ratio of the number of SNe Ia-pec to normal SNe Ia appears to be higher in early-type galaxies than it is in galaxies of later morphological types. This suggests that the ancestors of SNe Ia-pec may differ systematically in age or composition from the progenitors of normal SNe Ia. Unexpectedly, five SNe of Types Ib/c, II, and IIn (all of which are thought to have massive progenitors) are found in host galaxies that are nominally classified as types E and S0. However, in each case the galaxy classification is uncertain, or newly inspected images show evidence suggesting a later classification (abridged) ...Comment: Accepted for publishing in PAS

The Mass of the Centaurus A Group of Galaxies

The mass M, and the radius R_h, of the Centaurus A group are estimated from the positions and radial velocities of 30 probable cluster members. For an assumed distance of 3.9 Mpc it is found that R_h \sim 640 kpc. The velocity dispersion in the Cen A group is 114 \pm 21 km/s. From this value, and R_h = 640 kpc, the virial theorem yields a total mass of 1.4 \times 10^{13} M_{\sun} for the Cen A group. The projected mass method gives a mass of 1.8 \times 10^{13} M_{\sun}. These values suggest that the Cen A group is about seven times as massive as the Local Group. The Cen A mass-to-light ratio is found to be M/L_B = 155-200 in solar units. The cluster has a zero-velocity radius R_0 = 2.3 Mpc.Comment: 8 pages, 1 figure, in LaTeX format; to appear in the Astronomical Journal in January 200

Classifications of the Host Galaxies of Supernovae

Classifications on the DDO system are given for the host galaxies of 177 supernovae (SNe) that have been discovered since 1997 during the course of the Lick Observatory Supernova Search with the Katzman Automatic Imaging Telescope. Whereas SNe Ia occur in all galaxy types, it is found, at a high level of statistical confidence, that SNe Ib, Ic, and II are strongly concentrated in late-type galaxies. However, attention is drawn to a possible exception provided by SN 2001I. This SN IIn occurred in the E2 galaxy UGC 2836, which was not expected to harbor a massive young supernova progenitor.Comment: Accepted to be published in PAS

Are the Luminosities of RR Lyrae Stars Affected by Second Parameter Effects?

There is a serious discrepancy between the distance to the LMC derived from the Cepheid Period-Luminosity relation and that obtained by using the Galactic calibration for the luminosity of RR Lyrae stars. It is suggested that this problem might be due to the fact that second parameter effects make it inappropriate to apply Galactic calibrations to RR Lyrae variables in the Magellanic Clouds, i.e. Mv(RR) could depend on both [Fe/H] and on one or more second parameters.Comment: 10 pages as uuencoded compressed Postscript. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.htm

What are S0 (0) Galaxies?

Among early-type galaxies with almost circular isophotes E0 and E1 galaxies are, at 99.3% significance, more luminous than face-on objects classified as S0 (0) and S(0) (1). This result supports the view that rotation and "diskiness" are more important in the outer regions of faint-early type galaxies than they are for more luminous galaxies of very early morphological type.Comment: 7 pages. 0 figures. Astrophysical Jounral Letters in pres

The Luminosity Distribution of Local Group Galaxies

From a rediscussion of Local Group membership, and of distances to individual galaxies, we obtain $M_V$ values for 35 probable and possible Local Group members. The luminosity function of these objects is well fitted by a Schechter function with faint end slope $\alpha = -1.1 \pm 0.1$. The probability that the luminosity distribution of the Local Group is a single Schechter function with $\alpha$ steeper than -1.3 is less than 1 per cent. However, more complicated luminosity functions, such as multi-component Schechter functions with steep faint-end slopes, cannot be ruled out. There is some evidence that the luminosity distribution of dwarf spheroidal galaxies in the Local Group is steeper than that of dwarf irregular galaxies.Comment: 13 pages, 2 figures, accepted for publication in The Astronomical Journal. Figure 2 replaced, conclusion based on this figure change

Some Global Characteristics of the Galactic Globular Cluster System

The relations between the luminosities $M_{V}$, the metallicities $[Fe/H]$, the Galactocentric radii $R$, and the central concentration indices $c$ of Galactic globular clusters are discussed. It is found that the most luminous clusters rarely have collapsed cores. The reason for this might be that the core collapse time scales for such populous clusters are greater than the age of the Galaxy. Among those clusters, for which the structure has not been modified by core collapse, there is a correlation between central concentration and integrated luminosity, in the sense that the most luminous clusters have the strongest central concentration. The outermost region of the Galaxy with $R>10$ kpc was apparently not able to form metal-rich $([Fe/H]>-1.0)$ globular clusters, whereas such clusters (of which Ter 7 is the prototype) were able to form in some nearby dwarf spheroidal galaxies. It is not yet clear how the popular hypothesis that globular clusters were initially formed with a single power law mass spectrum can be reconciled with the observation that both (1) Galactic globular clusters with $R>80$ kpc, and (2) the globulars associated with the Sagittarius dwarf, appear to have bi-modal luminosity functions.Comment: 15 pages, 1 figur

Caltech Faint Galaxy Redshift Survey XV: Classification of Galaxies with 0.2 < z < 1.1 in the Hubble Deep Field (North) and its Flanking Fields

To circumvent the spatial effects of resolution on galaxy classification, the images of 233 objects of known redshift in the Hubble Deep Field (HDF) and its Flanking Fields (FF) that have redshifts in the range 0.20 < z < 1.10 were degraded to the resolution that they would have had if they were all located at a redshift z= 1.00. As in paper XIV of the present series, the effects of shifts in rest wavelength were mitigated by using R-band images for the classification of galaxies with 0.2 < z < 0.6 and I-band images for objects with redshifts 0.6 < z < 1.1. A special effort was made to search for bars in distant galaxies. The present data strongly confirm the previous conclusion that the Hubble tuning fork diagram only provides a satisfactory framework for the classification of galaxies with z ~< 0.3. More distant disk galaxies are often difficult to shoehorn into the Hubble classification scheme. The paucity of barred spirals and of grand-design spirals at large redshifts is confirmed. It is concluded that the morphology of disk galaxies observed at look-back times smaller than 3--4 Gyr differs systematically from that of more distant galaxies viewed at look-back times of 4--8 Gyr. The disks of late-type spirals at z >0.5 are seen to be more chaotic than those of their nearer counterparts. Furthermore the spiral structure in distant early-type spirals appears to be less well-developed than it is in nearby early-galaxies.Comment: Accepted for publication in the A