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We analyze the behavior of the parsec-scale jet of the quasar 3C 454.3 during pronounced flaring in 2005-2008. Three major disturbances propagated down the jet along different trajectories with Lorentz factors G > 10. The disturbances show a clear connection with millimeter-wave outbursts, in 2005 May/June, 2007 July, and 2007 December. High-amplitude optical events in the R-band light curve precede peaks of the millimeter-wave outbursts by 15-50 days. Each optical outburst is accompanied by an increase in X-ray activity. We associate the optical outbursts with propagation of the superluminal knots and derive the location of sites of energy dissipation in the form of radiation. The most prominent and long lasting of these, in 2005 May, occurred closer to the black hole, while the outbursts with a shorter duration in 2005 autumn and in 2007 might be connected with the passage of a disturbance through the millimeter-wave core of the jet. The optical outbursts, which coincide with the passage of superluminal radio knots through the core, are accompanied by systematic rotation of the position angle of optical linear polarization. Such rotation appears to be a common feature during the early stages of flares in blazars. We find correlations between optical variations and those at X-ray and g-ray energies. We conclude that the emergence of a superluminal knot from the core yields a series of optical and high-energy outbursts, and that the millimeter-wave core lies at the end of the jet's acceleration and collimation zone. We infer that the X-ray emission is produced via inverse Compton scattering by relativistic electrons of photons both from within the jet (synchrotron self-Compton) and external to the jet (external Compton, or EC); which one dominates depends on the physical parameters of the jet. A broken power-law model of the g-ray spectrum reflects a steepening of the synchrotron emission spectrum from near-IR to soft UV wavelengths. We propose that the g-ray emission is dominated by the EC mechanism, with the sheath of the jet supplying seed photons for g-ray events that occur near the millimeter-wave core.

We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size [?]2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology--including the nature of SMGs with multiple radio counterparts and constraints on the physical scale of the far infrared--of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim SMGs that peaks at higher redshift than previous, radio-selected samples. In particular, the presence of such a population of high-redshift sources has important consequences for models of galaxy formation--which struggle to account for such objects even under liberal assumptions--and dust production models given the limited time since the big bang.

We used the Extended Submillimeter Array (eSMA) in its most extended configuration to investigate the innermost (within a radius of [?]290 R * from the star) circumstellar envelope (CSE) of IRC+10216 where acceleration of gas and dust due to strong stellar radiation is taking place. We imaged the CSE using HCN and other molecular lines with a beam size of 0.''22 x 0.''46, deeply into the very inner edge ([?]15 R *) of the envelope where the expansion velocity is only [?]3 km s-1. The excitation mechanisms of hot HCN and KCl lines are discussed. HCN maser components are spatially resolved for the first time on an astronomical object. We identified two discrete regions in the envelope: a region with a radius of [?] 15 R *, where molecular species have just formed and the gas has begun to be accelerated (Region I) and a shell region (Region II) with a radius of 23 R * and a thickness of 15 R *, whose expansion velocity has reached up to 13 km s-1, nearly the terminal velocity of 15 km s-1. The Si34S line detected in Region I shows a large expansion velocity of 16 km s-1 due to strong wing components, indicating that the emission may arise from a shock region in the innermost envelope. In Region II, the position angle of the most copious mass-loss direction was found to be [?] 120deg +- 10deg, which may correspond to the equatorial direction of the star. Region II contains a torus-like feature. These two regions may have emerged due to significant differences in the size distributions of the dust particles in the two regions.

We have used the Submillimeter Array (SMA) to make the first interferometric observations (beam size [?]1'' or [?]400 pc) of the 12CO J = 6 - 5 line and 435 mm (690 GHz) continuum emission toward the central region (half power field of view 17'') of the nearby ultra-luminous infrared galaxy (ULIRG) Arp 220. These observations resolve the eastern and western nuclei from each other, in both the molecular line and dust continuum emission. At 435 mm, the peak intensity of the western nucleus is stronger than the eastern nucleus, and the difference in peak intensities is less than at longer wavelengths. Fitting a simple model to the dust emission observed between 1.3 mm and 435 mm suggests that dust emissivity power law index in the western nucleus is near unity and steeper in the eastern nucleus, about 2, and that the dust emission is optically thick at the shorter wavelength. Comparison with single dish measurements indicate that the interferometer observations are missing [?]60% of the dust emission, most likely from a spatially extended component to which these observations are not sensitive. The 12CO J = 6 - 5 line observations clearly resolve kinematically the two nuclei. The distribution and kinematics of the 12CO J = 6 - 5 line appear to be very similar to lower J CO lies observed at similar resolution. Analysis of multiple 12CO line intensities indicates that the molecular gas in both nuclei have similar excitation conditions, although the western nucleus is warmer and denser. The excitation conditions are similar to those found in other extreme environments, including the nearby starburst galaxy M82, the active galactic nucleus (AGN) hosting ULIRG Mrk 231, and the high-z QSO BR 1202-0725. Simultaneous lower resolution observations of the 12CO, 13CO, and C18O J = 2 - 1 lines show that the 13CO and C18O lines have similar intensities, which suggests that both of these lines are optically thick, or possibly that extreme high mass star formation has produced in an overabundance of C18O.

We present high-resolution submillimeter interferometric imaging of two of the brightest high-redshift submillimeter galaxies known: GN 20 and AzTEC1 at 0.8 '' and 0.3 '' resolution, respectively. Our data--the highest resolution submillimeter imaging of high-redshift sources accomplished to date--were collected in three different array configurations: compact, extended, and very extended. We derive angular sizes of 0.6 '' and 1.0 '' for GN 20 and 0.3 '' and 0.4 '' for AzTEC1 from modeling their visibility functions as a Gaussian and an elliptical disk, respectively. Because both sources are B-band dropouts, they likely lie within a relatively narrow redshift window around z [?] 4, which indicates their angular extent corresponds to physical scales of 4-8 and 1.5-3 kpc, respectively, for the starburst region. By way of a series of simple assumptions, we find preliminary evidence that these hyperluminous starbursts--with star formation rates >1000 M yr [?]1--are radiating at or close to their Eddington limit. Should future high-resolution observations indicate that these two objects are typical of a population of high-redshift Eddington-limited starbursts, this could have important consequences for models of star formation and feedback in extreme environments.

We have used the Submillimeter Array to image a flux-limited sample of seven submillimeter galaxies, selected by the AzTEC camera on the JCMT at 1.1 mm, in the COSMOS field at 890 m m with ~2'' resolution. All of the sources--two radio-bright and five radio-dim--are detected as single point sources at high significance (>6 s), with positions accurate to ~0.2'' that enable counterpart identification at other wavelengths observed with similarly high angular resolution. All seven have IRAC counterparts, but only two have secure counterparts in deep HST ACS imaging. As compared to the two radio-bright sources in the sample, and those in previous studies, the five radio-dim sources in the sample (1) have systematically higher submillimeter-to-radio flux ratios, (2) have lower IRAC 3.6-8.0 m m fluxes, and (3) are not detected at 24 m m . These properties, combined with size constraints at 890 m m ( th [?] 1.2''), suggest that the radio-dim submillimeter galaxies represent a population of very dusty starbursts, with physical scales similar to local ultraluminous infrared galaxies, with an average redshift higher than radio-bright sources.

We report new interferometric observations of the CO (2–1) rotational transition on Titan. We find that the spectrum is best fit by a uniform profile of 52 ppm, with estimated errors of 6 ppm (40 to 200 km) and 12 ppm (200 to 300 km).

Observations of CO at 2.6 mm (115.27 GHz) were made with the OVRO millimeter interferometer in 1986 and 1988, yielding high-quality disk-resolved spectra which were inverted to determine the CO mixing ratio profile from distinct regions on the disk, allowing us to map the distribution of CO in the upper mesosphere of Venus both horizontally and vertically. The 1986 observations were of the morning terminator and were particularly useful in searching for a suspected CO maximum ("bulge") on the nightside. The resulting CO mixing ratio profiles were mapped for various altitudes as functions of latitude and local time, and we report that we have resolved the previously inferred CO bulge. The bulge increases in magnitude from a small day-night variation at 90 km to an extensive nightside peak at 100 km, the upper limit of our observations. The peak bulge-to-dayside ratio approached 20-30 at 100 km in 1986 and may have been as large as 50-100, assuming late-afternoon CO abundances found in 1988 were similar to those in 1986. Three-dimensional mapping shows that in the upper mesosphere the bulge was displaced from local midnight toward the morning equator, centered at 3:30 AM local time. Using the qualitative model of mesospheric circulation on Venus proposed by Clancy and Muhleman (1985, Icarus64, 183-204; 1991, Icarus89, 129-146), we explain this shift in terms of strong retrograde zonal winds throughout the mesosphere, matching the directly detected mesospheric circulation (Shah, K., D. O. Muhleman, and G. L. Berge 1991, Icarus93, 96-121) observed with the same dataset in 1988.

IC 1613 has revealed a total of 77 H II regions, five of which are complexes of several smaller emission regions. Positions, H? luminosities, and sizes of these objects are tabulated. The H? luminosity function has the same shape as that for more luminous galaxies, following a power law with an exponent of -1.6. The faintest H II regions are at the low-luminosity end of the generally observed luminosity function for H II regions in galaxies, with fluxes of only ~1035erg/sec. The size distribution has an exponential shape, as for other galaxies, with a size scale of 56 pc. The morphologies of different H II regions are discussed and compared to those in other galaxies. Published radio continuum maps compare well with the H? emission distribution. The distribution of H I is also similar in the central areas to the H II with, however, a tendency for the H II regions to lie to one side of H I peaks.

We report on new microwave heterodyne observations of the CO J(1-0) rotational transition from the stratosphere of Titan made in October 1994 with the Owens Valley Radio Observatory millimeter array. The spectrum obtained clearly exhibits a strong emission core over the ~600-MHz bandwidth of the upper sideband spectrometer. The lineshape, referenced to the flat spectrum simultaneously observed in the lower sideband, was inverted to determine a best fit CO mixing ratio profile consistent with the observations. The best fit profile is a constant mixing ratio of 5 ± 1 × 10^-5 over the altitude range of 60-200 km. Combined with IR observations of tropospheric CO at 6 × 10^-5 (B. L. Lutz et al. 1983, Science 220, 1374-1375), this result provides strong evidence that CO is well mixed from the surface to at least 200 km in Titan's atmosphere. Copyright 1995, 1999 Academic Press

list of 96 galaxies brighter than V = 16.5 that are seen through the LMC and that are good candidates for probing the total optical extinction within the LMC. The search also registered a total of 1501 fainter galaxies. The number detected is strongly correlated with the position, decreasing greatly toward the center of the LMC. Because of crowding and uncertain completeness corrections, these figures allow only a rough estimate of the total extinction in the LMC as a function of distance from the center.