Adair P. Lane

Monochromatic phase curves and albedos for the lunar disk.

Photoelectric observations of the entire lunar disk made in 1964-1965 over phase angles from 6 to 12 deg in nine narrow bands from 0.35 to 1.0 microns and in UBV are reviewed. Phase curves are presented as a function of wavelength. The results confirm a reddening with increasing phase angle found by previous investigators for particular areas.

Detection of the 205 μm [N II] line from the Carina Nebula

We report the first detection of the 205 μm 3P1 P0 [N II] line from a ground-based observatory using a direct detection spectrometer. The line was detected from the Carina star formation region using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) on the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) at the South Pole. The [N II] 205 μm line strength indicates a low-density (n ~ 32 cm-3) ionized medium, similar to the low-density ionized halo previously reported in its [O III] 52 and 88 μm line emission. When compared with the Infrared Space Observatory [C II] observations of this region, we find that 27% of the [C II] line emission arises from this low-density ionized gas, but the large majority (~73%) of the observed [C II] line emission arises from the neutral interstellar medium. This result supports and underpins prior conclusions that most of the observed [C II] 158 μm line emission from Galactic and extragalactic sources arises from the warm, dense photodissociated surfaces of molecular clouds. The detection of the [N II] line demonstrates the utility of Antarctic sites for THz spectroscopy.

The AST/RO Survey of the Galactic Center Region. I. The Inner 3 Degrees

We present fully-sampled maps of 461 GHz CO (4-3), 807 GHz CO (7-6), and 492 GHz [CI] (3P1-3P0) emission from the inner 3 degrees of the Galactic Center region taken with the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) in 2001--2002. The data cover -1.3 70K) at cloud edges to low values (<50K) in the interiors. Typical gas pressures in the Galactic Center gas are n(H_2) T_kin approx 10^5.2 K cm^-3. We also present an (l,b) map of molecular hydrogen column density derived from our LVG results.

THE 492 GHz ATMOSPHERIC OPACITY AT THE GEOGRAPHIC SOUTH POLE

We present narrow-bandwidth submillimeter-wave sky opacity measurements made from the South Pole between 1995 February 9 and November 17, a period that includes an entire Austral winter. These measurements were made with the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) using a heterodyne receiver tuned to a band that includes the 492 GHz fine-structure line of neutral atomic carbon. The zenith optical depth was below 0.72 half the time during the Austral winter and spring, and it reached values as low as 0.34 on day 232. The stability was also remarkably good: the opacity remained below 1.0 for weeks at a time. The South Pole is therefore an excellent site for submillimeter astronomy throughout the Austral winter and spring. The functional relationship between 492 GHz opacity and measured precipitable water vapor shows that a significant fraction of the opacity is caused by atmospheric constituents other than water vapor, indicating the need for accurate, site-dependent atmospheric modeling when opacity measurements at lower frequencies are extrapolated into the submillimeter.

H2O masers in circumstellar envelopes

The spatial structure of H/sub 2/O maser emission at 22.235 GHz for 12-late-type variable stars has been measured with a resolution of 0.07 arcsec. The H/sub 2/O maser regions of Mira variables range from 9 or less to 108 AU in total extent, while those of supergiant long-period variables are 300-720 AU in extent. The size of the H/sub 2/O maser regions of giants and supergiants is correlated with the stellar mass-loss rate. Several of the observed sources show evidence for nonspherical geometry in the distribution of their H/sub 2/O maser emission. The Mira variable IK Tau exhibits about 31 maser features over a total velocity range of 41 km/s. The spatial distribution of these features appears to be consistent with two spherical shells of radii 25 and 59 AU, both expanding at a velocity of 15.5 km/sec from the star. Evidence is found for density inhomogeneities and turbulent motions in the envelopes of both IK Tau and R Aql. 34 references.

A 205 μm [N II] MAP OF THE CARINA NEBULA

We present the results of a � 250 arcmin 2 mapping of the 205 �m [NII] fine-structure emission over the northern Carina Nebula, including the Car I and Car II HII regions. Spectra were obtained using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) at the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) at South Pole. We supplement the 205 �m data with new reductions of far-IR fine-structure spectra from the Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) in 63 �m [OI], 122 �m [NII], 146 �m [OI], and 158 �m [CII]; the 146 �m [OI] data include 90 raster positions which have not been previously published. Morphological comparisons are made with optical, radio continuum and CO maps. The 122/205 line ratio is used to probe the density of the low-ionization gas, and the 158/205 line ratio is used to probe the fraction of C + arising from photodissociation regions (PDRs). The [OI] and [CII] lines are used to construct a PDR model of Carina. When the PDR properties are compared with other sources, Carina is found to be more akin to 30 Doradus than galactic star-forming regions such as Orion, M17, or W49; this is consistent with the view of Carina as a more evolved region, where much of the parent molecular cloud has been ionized or swept away. These data constitute the first ground-based detection of the 205 �m [NII] line, and the third detection overall since those of the COBE FIRAS and the KAO in the early 1990s. Subject headings: HII regions — infrared: ISM — ISM: individual (Carina nebula) — ISM: lines and bands — photon-dominated region (PDR) — submillimeter: ISM

AST/RO Observations of Atomic Carbon near the Galactic Center

We present a coarsely sampled map of the region |l| ≤ 2°, |b| ≤ 01 in the 492 GHz (3P1 → 3P0) fine-structure transition of neutral carbon, observed with the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO). The distribution of [C I] emission is similar on the large scale to that of CO J = 1 → 0. On average, the ratio of the integrated intensities, I[C I]/I12CO, is higher in the Galactic disk than in the Galactic center region. This result is accounted for by the absorption of 12CO within the clouds located in the outer Galactic disk. The ratio I[C I]/I12CO is surprisingly uniform over the variety of environments near the Galactic center. On average, [C I] is optically thin [or as optically thin as 13CO (J = 1 → 0)], even in the dense molecular clouds of the Galactic center region.

Atomic Carbon in Southern Hemisphere High-Latitude Clouds

We report the detection of atomic carbon in a sample of eight southern hemisphere high Galactic latitude molecular clouds, using the Antarctic Submillimeter Telescope and Remote Observatory. The 492 GHz (3P1 →3P0) transition of [C I] was detected in all of the clouds observed. The C/CO column density ratio ranges from 0.4 to 2.5 and is similar to the values previously measured in high-latitude clouds MBM 12 and HD 210121. For all 10 high-latitude clouds observed in [C I], C/CO averages ~1.2 and decreases with increasing total gas column density NH, as predicted by translucent cloud models. Quantitative comparison with chemical models of homogeneous clouds is unsatisfactory, however, and we conclude that the clumpy structure of clouds must be taken into account in order to interpret the data properly.

Gas Density, Stability, and Starbursts near the Inner Lindblad Resonance of the Milky Way

A key project of the Antarctic Submillimeter Telescope and Remote Observatory reported by Martin et al. is the mapping of CO J = 4 → 3 and J = 7 → 6 emission from the inner Milky Way, allowing determination of gas density and temperature. Galactic center gas that Binney et al. identify as being on x2 orbits has a density near 103.5 cm-3, which renders it only marginally stable against gravitational coagulation into a few giant molecular clouds, as discussed by Elmegreen. This suggests a relaxation oscillator mechanism for starbursts in the Milky Way, whereby inflowing gas accumulates in a ring at 150 pc radius until the critical density is reached and the resulting instability leads to the sudden formation of giant clouds and the deposition of 4 × 107 M☉ of gas onto the Galactic center. Depending on the accretion rate near the inner Lindblad resonance, this cycle will repeat with a timescale of order 20 Myr.

FIRST DETECTION OF 492 GHz (C I) EMISSION FROM THE LARGE MAGELLANIC CLOUD

The 3 P1 3 3 P0 fine-structure transition of neutral atomic carbon [C I] was observed with the Antarctic Submillimeter Telescope and Remote Observatory (ASTyRO) toward two star-forming regions in the Large Magellanic Cloud: N159 and 30 Doradus. The [C I] line is weak in the vicinity of 30 Dor, a region with a uniquely hard and intense UV field. The I[C I]yICO ratio in N159 is enhanced by a factor?2 compared to the Milky Way Galaxy, a result attributable to the lower metallicity of the Large Magellanic Cloud. Subject headings: galaxies: ISM—ISM: atoms—ISM: individual (N159, 30 Doradus)—Magellanic Clouds— radio lines: ISM