M. J. Pierce

Luminosity-line width relations and the extragalactic distance scale. I - Absolute calibration

Multicolor CCD photometry is presented for a sample of 15 spiral and irregular members of the Local, Sculptor, and M81 groups with M B ≤ -16.0 and relevant as potential calibrators of the luminosity-line width relations. The sample contains those galaxies for which a ground-based study of Cepheid variables could provide accurate distances and hence an absolute calibration for the relations. Unfortunately, only six of the systems presently have reliable independent distance estimates, but this number is sufficient to provide a reasonable calibration

Nearby galaxy flows modeled by the light distribution - Distances, model, and the local velocity anomaly

Supporting material for the article of Shaya et al. (1992, ApJ) is presented. One table gives measured galaxy distances used to construct a map of observed peculiar velocities, and another table gives a grid of the distribution of light used to construct a map of expected peculiar velocities. A preferred model was developed which gave a best fit between these maps, and this model has been used to generate output kinematic distances which are recorded here for groups and individual galaxies with V 0 < 3000 km/s

High-resolution imaging of distant clusters. I : Close pairs, interactions, and the Butcher-Oemler' effect at z=0.4

We present new ground-based high-resolution images of 23 blue galaxies whose membership has been confirmed spectroscopically in the two distant rich clusters Abell 370 and Cl 0024+1654. The images, taken with the High Resolution Camera on the CFHT, have a stellar FWHM=0.45 arcsec. Ten of these blue galaxies are found to have close companions, with separations on the scale of 1 to 2 arcsec. These multiple systems represent 45% of the confirmed blue galaxy population in the two clusters. Several of the remaining blue galaxies also have peculiar morphologies and features, such as tidal tails, suggestive of interactions/mergers

Constraints on the Hubble constant from observations of the brightest red-giant stars in a Virgo-cluster galaxy

The nearest large groups of elliptical galaxies, in the Virgo and Fornax clusters, play a central role in determinations of the Hubble constant, H0, and hence the cosmological rate of expansion. Because the relative distances between these two clusters and more remote clusters are well known, absolute distance determinations to Virgo and Fornax should establish the Hubble constant for the local Universe. In addition, elliptical galaxies reside predominantly in the cores of clusters, so distance calibrations for ellipticals should minimize the uncertainties due to the possibly large extent of the clusters along the line of sight. A powerful and direct way of establishing such distances is to use thebrightest red-giant stars, which have nearly uniform luminosities,. Here we report the direct observation of old red-giant stars in a dwarf elliptical galaxy in the Virgo cluster. We determine a distance to this galaxy, and thus to the core of the Virgo cluster, of 15.7 ± 1.5 megaparsecs, from which we estimate a Hubble constant of H0 = 77 ± 8 km s−1 Mpc−1. Under the assumption of a low-density Universe with the simplest cosmology, the age of the Universe is no more than 12–13 billion years.

Near-infrared (JHK) Photometry of 131 Northern Galactic Classical Cepheids

Near-infrared photometric measurements for 131 Northern Galactic Cepheids are presented. The Cepheid light curves are sampled with an average of 22 measurements per star fully covering the phase of each Cepheid. The J, H, and K light curves for each Cepheid were uniformly interpolated to find the intensity mean magnitudes within each band. The results are consistent within ±1% for 26 stars in common with previous studies. This paper is the first in a projected series of two papers which will provide additional fundamental data for Cepheids in the Galaxy, namely, NIR photometry and line-of-sight extinction. In the course of this project, 93 additional variables were fortuitously observed within the Cepheid program fields, 82 of which have previously not been identified.

The frequency of mid-infrared excess sources in galactic surveys

We have identified 230 Tycho-2 Spectral Catalog stars that exhibit 8 μm mid-IR extraphotospheric excesses in the MSX and Spitzer GLIMPSE surveys. Of these, 183 are either OB stars earlier than B8 in which the excess plausibly arises from a thermal bremsstrahlung component or evolved stars in which the excess may be explained by an atmospheric dust component. The remaining 47 stars have spectral classifications B8 or later and appear to be main-sequence or late pre-main-sequence objects harboring circumstellar disks. Six of the 47 stars exhibit multiple signatures characteristic of pre-main-sequence circumstellar disks, including emission lines, near-IR K-band excesses, and X-ray emission. Approximately one-third of the remaining 41 sources have emission lines suggesting relative youth. We modeled the excesses in 26 stars having two or more measurements in excess of the expected photospheres as single-component blackbodies. We determine probable disk temperatures and fractional IR luminosities in the range 191 K < T < 787 K and 3.9 × 10-4 < LIR/L* < 2.7 × 10-1. The majority of our modeled sample (14 stars) have 10-3 < LIR/L* < 10-2 and are consistent with either transition disks or massive debris disks. These objects have fractional IR luminosities and temperatures between those of β Pic-type debris disk systems (LIR/L* ≤ 10-3) and Class II pre-main-sequence systems (LIR/L* 10-1). We estimate a lower limit on the fraction of Tycho-2 Spectral Catalog main-sequence stars having mid-IR, but not near-IR, excesses to be 1.0% ± 0.3%.

Nearby galaxy flows modeled by the light distribution

The observed distribution of light in the Local Supercluster has been used to determine the expected velocities of galaxies if the assumptions are valid that nonexpansion motions are generated by gravitational perturbations and that mass is distributed like the light. Since detailed knowledge of the light distribution extends to only 3000 km s −1 , three extra sources are added at large distances: one associated with the Great Attractor, one loosely with the Perseus-Pisces Supercluster region, and one with the Shapley Concentration at a distance corresponding to 13,800 km s −1

Stellar ovals and nuclear rings in the interior of M51 and M100

CCD images taken in the B, R, and I passbands have revealed substantial stellar ovals in the interior region (about 1 kpc) of the two nearby Sc galaxies M51 and M100. The amplitude of the azimuthal intensity variation is found to be 25 percent and 45 percent, respectively. The ovals are associated with both noncircular streaming motions and enhanced star formation. Blue (B - I about 0.8) rings of star formation are found near the outer boundary of the ovals. The close association of the star-forming rings and the ovals with the estimated position of the galaxys inner Lindblad resonance (ILR) suggests a dynamical connection between the ovals and the ILR. Interestingly, M100 possess both an inner oval (within the ILR) and a classical bar (extending to near the expected radius for corotation). 48 references.

Classification of galaxies on CCD frames

Morphological classifications of 231 galaxies in and near the Virgo and Ursa Major clusters are reported which show that luminosity classification techniques (LCTs) can be used to determine the luminosities of spiral galaxies with an accuracy of about 0.7 mag on CCD frames. The observations in the direction of the Virgo Cluster confirm the assignment of some galaxies to the background field, strongly confirming that the large dispersion in the Tully-Fisher relation for Virgo galaxies is at least partly due to contamination of the Virgo core sample by background galaxies. LCTs yield a distance of 15.3 + 2.6 or - 2.2 Mpc for the spiral and irregular galaxies associated with the core of the Virgo Cluster proper. The Ursa Major and Virgo cluster distances are found to be the same. A class of galaxies with fuzzy, anemic outer structure and active star formation in their cores is found to be common in Virgo but rare in the Ursa Major Cluster. 31 refs.

High-resolution imaging of Virgo Cluster galaxies. I: The distance based on the brightest stars in NGC 4571

Deep, high-resolution images (FWHM=0″.43) of a relatively face-on, late-type spiral galaxy (NGC 4571) in the Virgo Cluster have been obtained using the High-Resolution Camera (HRCam) and the Canada-France-Hawaii Telescope. The galaxy is apparently resolved into stars. The combined image has a limiting magnitude of m R ∼26, enabling the brightest three magnitudes of the luminosity function to be examined, where the photometry is complete. Point-spread function fitting photometric techniques (i.e., DAOPHOT) are applied to the data allowing the application of quantitative and objective criteria for distinguishing stars from H II regions and compact clusters/associations