ISOCAM Mid-Infrared Imaging of the Quiescent Spiral Galaxy NGC 7331

Using the mid-infrared camera (ISOCAM) on the Infrared Space Observatory (ISO), the Sb LINER galaxy NGC 7331 has been imaged in two broadband and four narrowband filters between 6.75 and 15 microns. These maps show a prominent circumnuclear ring of radius 0.25 arcminutes X 0.75 arcminutes (1.1 X 3.3 kpc) encircling an extended central source. The 7.7 and 11.3 micron dust emission features are strong in this galaxy, contributing approximately 1/3 of the total IRAS 12 micron broadband flux from this galaxy. In contrast to starburst galaxies, the 15 micron continuum is weak in NGC 7331. The mid-infrared spectrum does not vary dramatically with position in this quiescent galaxy, showing neither large-scale destruction of the carriers of the emission bands or a large increase in the 15 micron continuum in the star forming ring. In the bulge, there is some enhancement of the 6.75 micron flux, probably because of contributions from photospheric light, however, the 11.3 micron dust feature is also seen, showing additional emission from interstellar or circumstellar dust.Comment: 17 pages, 6 figures (figure 3 in color) To appear in the Astrophysical Journa

Interstellar Gas in Low Mass Virgo Cluster Spiral Galaxies

We have measured the strengths of the [C II] 158 micron, [N II] 122 micron, and CO (1 - 0) lines from five low blue luminosity spiral galaxies in the Virgo Cluster, using the Infrared Space Observatory and the NRAO 12m millimeter telescope. Two of the five galaxies have high L([C II)]/L(CO) and L(FIR)/L(CO) ratios compared to higher mass spirals. These two galaxies, NGC 4294 and NGC 4299, have L([C II])/L(CO) ratios of >14,300 and 15,600, respectively, which are similar to values found in dwarf irregular galaxies. This is the first time that such enhanced L([C II])/L(CO) ratios have been found in spiral galaxies. This result may be due to low abundances of dust and heavy elements, which can cause the CO (1 - 0) measurements to underestimate the molecular gas content. Another possibility is that radiation from diffuse HI clouds may dominate the [C II] emission from these galaxies. Less than a third of the observed [C II] emission arises from HII regions.Comment: 24 pages, Latex, 2 Figures, 6 Tables To appear in the Astronomical Journal, July 199

High Spatial Resolution KAO Far-Infrared Observations of the Central Regions of Infrared-Bright Galaxies

We present new high spatial resolution Kuiper Airborne Observatory 50 micron and/or 100 micron data for 11 infrared-bright galaxies. We also tabulate previously published KAO data for 11 other galaxies, along with the IRAS data for the bulges of M 31 and M 81. We find that L(FIR)/L(B) and L(FIR)/L(H) correlate with CO (1 - 0) intensity and tau(100). Galaxies with optical or near-infrared signatures of OB stars in their central regions have higher values of I(CO) and tau(100), as well as higher far-infrared surface brightnesses and L(FIR)/L(B) and L(FIR)/L(H) ratios. L(FIR)/L(H(alpha)) does not correlate strongly with CO and tau(100). These results support a scenario in which OB stars dominate dust heating in the more active galaxies and older stars are important in quiescent bulges.Comment: 45 pages, to appear in Ap.J. vol. 468 (Sept. 1996). 17 postscript figures and 10 postscript tables available at ftp://ipac.caltech.edu/science/bsmith/ka

Phase Lags in the Optical-Infrared Light Curves of AGB Stars

To search for phase lags in the optical-infrared light curves of asymptotic giant branch stars, we have compared infrared data from the COBE DIRBE satellite with optical light curves from the AAVSO and other sources. We found 17 examples of phase lags in the time of maximum in the infrared vs. that in the optical, and 4 stars with no observed lags. There is a clear difference between the Mira variables and the semi-regulars in the sample, with the maximum in the optical preceding that in the near-infrared in the Miras, while in most of the semi-regulars no lags are observed. Comparison to published theoretical models indicates that the phase lags in the Miras are due to strong titanium oxide absorption in the visual at stellar maximum, and suggests that Miras pulsate in the fundamental mode, while at least some semi-regulars are first overtone pulsators. There is a clear optical-near-infrared phase lag in the carbon-rich Mira V CrB; this is likely due to C2 and CN absorption variations in the optical.Comment: AJ, in pres

Beverly Smith Babb in a Senior Voice Recital

This is the program for the senior voice recital of Beverly Smith Babb. Pianist Sheryl Waters accompanied the performance. This recital took place on April 27, 1980, in the Mabee Fine Arts Center Recital Hall

Optical imaging of IRAS galaxies : the evolution of infrared- bright galaxies.

Gravitational interactions play an important role in galaxy evolution, both in causing rapid structural changes in individual galaxies, and in changing the overall properties of galaxies over the age of the Universe. Galaxy interactions have also been linked to high far-infrared luminosities and Seyfert activity. In this thesis, the relationship between far-infrared luminosity and interactions is explored by means of an I-band CCD imaging survey of a 60 $\mu$m flux-limited sample of 275 galaxies. The galaxies in this sample are classified as interacting or non-interacting based on the information in these images. The definition of an interacting pair used here is: the companion galaxy must have at least 1/4 the I-band luminosity of the infrared galaxy, the separation between the two must be less than three times the larger radius, and the velocity difference for the two galaxies must be less than 500 km/s. It is found that 56 of these galaxies are interacting, 198 are non-interacting, and 21 are ambiguous. The interacting galaxies have an average 60 $\mu$m luminosity of $\sim$6 times that of the non-interacting galaxies, consistent with numerical models of interacting galaxies. The 60 $\mu$m luminosity functions $\phi$(L) of interacting galaxies and of non-interacting galaxies are then derived. Non-interacting galaxies dominate the luminosity function at low luminosities, while interacting dominate at high luminosities. The luminosity function of non-interacting galaxies drops off fairly steeply at {\rm L \u3e 10\sp{10}L\sb{o}(\phi(L) \propto L\sp{-2.1})}, while that of interacting galaxies is flatter {\rm (\phi(L) \propto L\sp{-1.2})}. There are $\sim$5 times as many non-interacting galaxies as interacting galaxies having L(60) $\u3e$ L(MILKY WAY), and $\sim$100 times more having L(60) $\u3e$ 2 $\times$ 10\sp8L\sb{\rm o}. The derived luminosity functions of interacting and non-interacting galaxies are used to predict 60 $\mu$m source counts in deeper surveys. If only interacting galaxies are assumed to evolve, the predicted source counts are 60-80% those determined if all galaxies evolve. Assuming the I-band light ratio approximates the mass ratio, the 60 $\mu$m luminosity is compared with mass ratio and with pair separation. It is found that the mean luminosity of pairs with separation greater than 3 times the radius is similar to that of galaxies without bound companions, suggesting that encounters between galaxies with separations greater than three times the radius do not greatly enhance the star formation rate. Additionally, low mass companions (m\sb1/m\sb2) are not found to greatly enhance the far-infrared luminosity