Hubble Space Telescope Planetary Camera Images of NGC 1316

We present HST Planetary Camera V and I~band images of the central region of the peculiar giant elliptical galaxy NGC 1316. The inner profile is well fit by a nonisothermal core model with a core radius of 0.41" +/- 0.02" (34 pc). At an assumed distance of 16.9 Mpc, the deprojected luminosity density reaches \sim 2.0 \times 10^3 L_{\sun} pc$^{-3}$. Outside the inner two or three arcseconds, a constant mass-to-light ratio of $\sim 2.2 \pm 0.2$ is found to fit the observed line width measurements. The line width measurements of the center indicate the existence of either a central dark object of mass 2 \times 10^9 M_{\sun}, an increase in the stellar mass-to-light ratio by at least a factor of two for the inner few arcseconds, or perhaps increasing radial orbit anisotropy towards the center. The mass-to-light ratio run in the center of NGC 1316 resembles that of many other giant ellipticals, some of which are known from other evidence to harbor central massive dark objects (MDO's). We also examine twenty globular clusters associated with NGC 1316 and report their brightnesses, colors, and limits on tidal radii. The brightest cluster has a luminosity of 9.9 \times 10^6 L_{\sun} ($M_V = -12.7$), and the faintest detectable cluster has a luminosity of 2.4 \times 10^5 L_{\sun} ($M_V = -8.6$). The globular clusters are just barely resolved, but their core radii are too small to be measured. The tidal radii in this region appear to be $\le$ 35 pc. Although this galaxy seems to have undergone a substantial merger in the recent past, young globular clusters are not detected.Comment: 21 pages, latex, postscript figures available at ftp://delphi.umd.edu/pub/outgoing/eshaya/fornax

VII Zw 403: H I structure in a blue compact dwarf galaxy

‘In these times, during the rise in the popularity of institutional repositories, the Society does not forbid authors from depositing their work in such repositories. However, the AAS regards the deposit of scholarly work in such repositories to be a decision of the individual scholar, as long as the individual's actions respect the diligence of the journals and their reviewers.’ Original article can be found at : http://iopscience.iop.org/ Copyright American Astronomical SocietyWe present optical (UBVJ), ultraviolet (FUV, NUV), and high-resolution atomic hydrogen (H I) observations of the nearby blue compact dwarf (BCD), VII Zw 403. We find that VII Zw 403 has a relatively high H I mass-to-light ratio for a BCD. The rotation velocity is nominally 10-15 km s(-1), but rises to similar to 20 km s(-1) after correction for the similar to 8-10 km s(-1) random motions present in the gas. The velocity field is complex, including a variation in the position angle of the major axis going from the northeast to the southwest parts of the galaxy. Our high-resolution Hi maps reveal structure in the central gas, including a large, low-density Hi depression or hole between the southern and northern halves of the galaxy, coincident with an unresolved X-ray source. Although interactions have been proposed as the triggering mechanism for the vigorous star formation occurring in BCDs, VII Zw 403 does not seem to have been tidally triggered by an external interaction, as we have found no nearby possible perturbers. It also does not appear to fall in the set of galaxies that exhibit a strong central mass density concentration, as its optical scale length is large in comparison to similar systems. However, there are some features that are compatible with an accretion event: optical/Hi axis misalignment, a change in position angle of the kinematic axis, and a complex velocity field.Peer reviewe

Hubble Space Telescope Observations of M32: The Color-Magnitude Diagram

We present a V-I color-magnitude diagram for a region 1'-2' from the center of M32 based on Hubble Space Telescope WFPC2 images. The broad color-luminosity distribution of red giants shows that the stellar population comprises stars with a wide range in metallicity. This distribution cannot be explained by a spread in age. The blue side of the giant branch rises to M_I ~ -4.0 and can be fitted with isochrones having [Fe/H] ~ -1.5. The red side consists of a heavily populated and dominant sequence that tops out at M_I ~ -3.2, and extends beyond V-I=4. This sequence can be fitted with isochrones with -0.2 < [Fe/H] < +0.1, for ages running from 15 Gyr to 5 Gyr respectively. We do not find the optically bright asymptotic giant branch stars seen in previous ground-based work and argue that the majority of them were artifacts of crowding. Our results are consistent with the presence of the infrared-luminous giants found in ground-based studies, though their existence cannot be directly confirmed by our data. There is little evidence for an extended or even a red horizontal branch, but we find a strong clump on the giant branch itself. If the age spread is not extreme, the distribution of metallicities in M32 is considerably narrower than that of the closed-box model of chemical evolution, and also appears somewhat narrower than that of the solar neighborhood. Overall, the M32 HST color-magnitude diagram is consistent with the average luminosity-weighted age of 8.5 Gyr and [Fe/H] = -0.25 inferred from integrated spectral indices.Comment: 22 pages, AASTeX, aaspp4 and flushrt style files included, 11 postscript figures, figures 1,2,5,7, and 8 available at ftp://bb3.jpl.nasa.gov/pub/m32 . Submitted to the Astronomical Journa

The Luminosity Function and Mass Function in the Galactic Bulge

We present deep photometry obtained with the Hubble Space Telescope (HST) in a field in Baade's Window in the Galactic bulge. We derive a luminosity function down to I ~ 24.3, or V ~ 27.5, corresponding to M ~ 0.3 Msun. The luminosity function from the turnoff down to this level appears remarkably similar to that observed in the solar neighborhood. We derive a mass function using both an empirical local mass-luminosity relation and a mass-luminosity relation from recent stellar model calculations, allowing for the presence of binaries and photometric errors. The mass function has a power law form with dN/dM proportional to M^{-2.2} for M >~ 0.7 Msun. However, we find strong evidence for a break in the mass function slope around 0.5-0.7 Msun, with a significantly shallower slope at lower masses. The value of the slope for the low masses depends on the assumed binary fraction and the accuracy of our completeness correction. This mass function should directly reflect the initial mass function.Comment: 26 pages, 9 figures, to be published in the Astronomical Journa

Hubble Space Telescope Planetary Camera images of R136

The Planetary Camera of the Hubble Space Telescope has been used to obtain broad and narrowband images ofR136, the core of the massive star cluster 30 Doradus in the Large Magellanic Cloud. R136a, the brightest component ofR136, is shown to have at least 12 separate components, including the eight originally identified by speckle interferometry. Three of the 12 components are previously unidentified close companions of the speckle components. The stars within R136a are found to have luminosities and colors of normal evolved (Wolf-Rayet and blue supergiants) and zero-age main-sequence (ZAMS) massive stars. A narrowband He II filter was used to investigate the Wolf-Rayet stellar population. We find that three stars in R136a are of the Wolf-Rayet type; of the two identified from ground-based data, one is now resolved into two components. We present color-magnitude diagrams and a luminosity function of the stars within the larger region (~2 pc) defined as R136. We find that the stars in R136 are similar in color and luminosity to those of cluster members that lie outside that crowded inner region. The lower end of the color-magnitude diagram corresponds to ZAMS spectral type B3. No red supergiants have been detected within R136. The luminosity per unit area in the inner 1" (0.25 pc) of R136 is ≥ 50 times that of the center of Orion for a comparable area and seven times that of the core of NGC 3603. The luminosity per unit area of all of R136 is comparable to that of Orion but is sustained over 130 times the area. An F336W surface brightness profile is constructed for R136 based on the stellar photometry. The distribution is found to be consistent with a pure power law with l(r}ɑ r^y with y=-1.72±0.06 or with a small core with r_c 5 X 10^4 M_☉ pc^(-3). The implied upper limit on the relaxation time for the cluster is much smaller than the age of 3.5 X 10^6 yrs required by the presence of Wolf-Rayet stars. This suggests that relaxation effects have been very important in determining the observed structure of the cluster unless a large population of lower mass stars is also present

The core of the nearby S0 galaxy NGC 7457 imaged with the HST planetary camera

We have observed the nearby S0 galaxy NGC 7457 with the Planetary Camera of the Hubble Space Telescope. Spatial structure is observable at the diffraction-limited resolution of the 2.4 m HST primary despite the effects of spherical aberration. The central distribution of starlight appears consistent with a y ~ -1.0 power law for r 3 x 10^4 L_☉ pc^(-3) (V band). This is now the second densest core known after M32. From the ground, NGC 7457 resembles any number of unresolved elliptical galaxies, which suggests that compact dense cores may be common. The images of NGC 7457 demonstrate that HST can still provide unique and astrophysically interesting information on the central structure of galaxies

Imaging of the gravitational lens system PG 1115+080 with the Hubble Space Telescope

This paper is the first of a series presenting observations of gravitational lenses and lens candidates, taken with the Wide Field/Planetary Camera (WFPC) of the Hubble Space Telescope (HST). We have resolved the gravitational lens system PG 1115 + 080 into four point sources and a red, extended object that is presumably the lens galaxy; we present accurate relative intensities, colors, and positions of the four images, and lower accuracy intensity and position of the lens galaxy, all at the epoch 1991.2. Comparison with earlier data shows no compelling evidence for relative intensity variations between the QSO components having so far been observed. The new data agree with earlier conclusions that the system is rather simple, and can be produced by the single observed galaxy. The absence of asymmetry in the HST images implies that the emitting region of the quasar itself has an angular radius smaller than about 10 milliarcsec (100 pc for H_0=50, q_0=0.5)