ABSTRACT
The aim of this work is to study structure and gas kinematics in the photodissociation regions (PDRs) around the compact H ii regions S235 A and S235 C. We observe the C ii, 13C ii, and O i ...line emission, using SOFIA/upGREAT, and complement them by data of HCO+ and CO. We use the 13C ii line to measure the optical depth of the C ii emission, and find that the C ii line profiles are influenced by self-absorption, while the 13C ii line remains unaffected by these effects. Hence, for dense PDRs, 13C ii emission is a better tracer of gas kinematics. The optical depth of the C ii line is up to 10 in S235 A. We find an expanding motion of the C ii-emitting layer of the PDRs into the front molecular layer in both regions. Comparison of the gas and dust columns shows that gas components visible neither in the C ii nor in low-J CO lines may contribute to the total column across S235 A. We test whether the observed properties of the PDRs match the predictions of spherical models of expanding H ii region + PDR + molecular cloud. Integrated intensities of the 13C ii, C ii, and O i lines are well represented by the model, but the models do not reproduce the double-peaked C ii line profiles due to an insufficient column density of C+. The model predicts that the O i line could be a more reliable tracer of gas kinematics, but the foreground self-absorbing material does not allow using it in the considered regions.
ABSTRACT We present initial results of very high resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the z = 3.042 gravitationally lensed submillimeter galaxy HATLAS ...J090311.6+003906 (SDP.81). These observations were carried out using a very extended configuration as part of Science Verification for the 2014 ALMA Long Baseline Campaign, with baselines of up to ∼15 km. We present continuum imaging at 151, 236, and 290 GHz at unprecedented angular resolutions as fine as 23 mas, corresponding to an unmagnified spatial scale of ∼180 pc at z = 3.042. The ALMA images clearly show two main gravitational arc components of an Einstein ring, with emission tracing a radius of ∼1 5. We also present imaging of CO J = 10 − 9, J = 8 − 7, and J = 5 − 4 and ) line emission. The CO emission, at an angular resolution of ∼170 mas, is found to broadly trace the gravitational arc structures but with differing morphologies between the CO transitions and compared to the dust continuum. Our detection of line emission, using only the shortest baselines, provides the most resolved detection to date of thermal emission in an extragalactic source. The ALMA continuum and spectral line fluxes are consistent with previous Plateau de Bure Interferometer and Submillimeter Array observations despite the impressive increase in angular resolution. Finally, we detect weak unresolved continuum emission from a position that is spatially coincident with the center of the lens, with a spectral index that is consistent with emission from the core of the foreground lensing galaxy.
We derive molecular-gas-phase 12 C/ 13 C isotope ratios for the central few hundred parsecs of the three nearby starburst galaxies NGC 253, NGC 1068, and NGC 4945 making use of the λ ∼ 3 mm 12 CN and ...13 CN N = 1–0 lines in the ALMA Band 3. The 12 C/ 13 C isotopic ratios derived from the ratios of these lines range from 30 to 67 with an average of 41.6 ± 0.2 in NGC 253, from 24 to 62 with an average of 38.3 ± 0.4 in NGC 1068, and from 6 to 44 with an average of 16.9 ± 0.3 in NGC 4945. The highest 12 C/ 13 C isotopic ratios are determined in some of the outskirts of the nuclear regions of the three starburst galaxies. The lowest ratios are associated with the northeastern and southwestern molecular peaks of NGC 253, the northeastern and southwestern edge of the mapped region in NGC 1068, and the very center of NGC 4945. In the case of NGC 1068, the measured ratios suggest inflow from the outer part of NGC 1068 into the circum-nuclear disk through both the halo and the bar. Low 12 C/ 13 C isotopic ratios in the central regions of these starburst galaxies indicate the presence of highly processed material.
Aims. Our aim is to derive carbon isotopic ratios from optically thin tracers in the central regions of the starburst galaxies M 82 and NGC 253. Methods. We present high-sensitivity observations of ...CCH and two of its super(13)C isotopologues, C super(13)CH and super(13)CCH, as well as the optically thin emission from C super(18)O and super(13)C super(18)O. We assume the column density ratio between isotopologues is representative of the super(12)C/ super(13)C isotopic ratio. Results. From CCH, lower limits to the super(12)C/ super(13)C isotopic ratio of 138 in M 82, and 81 in NGC 253, are derived. Lower limits to the super(12)C/ super(13)C ratios from CO isotopologues support these. super(13)C super(18)O is tentatively detected in NGC 253, which is the first reported detection in the extragalactic ISM. Based on these limits, we infer ratios of super(16)O/ super(18)O > 350 and > 300 in M 82 and NGC 253, respectively, and super(32)S/ super(34)S >16 in NGC 253. The derived CCH fractional abundances toward these galaxies of less than or approximate to 1.1 x 10 super(-8) agree well with those of molecular clouds in the Galactic disk. Conclusions. Our lower limits to the super(12)C/ super(13)C ratio from CCH are a factor of 2-3 larger than previous limits. The results are discussed in the context of molecular and nucleo-chemical evolution. The high super(12)C/ super(13)C isotopic ratio of the molecular ISM in these starburst galaxies suggest that the gas has been recently accreted toward their nuclear regions.
ABSTRACT We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum images of the asteroid 3 Juno obtained with an angular resolution of (60 km at 1.97 AU). The data were ...obtained over a single 4.4 hr interval, which covers 60% of the 7.2 hr rotation period, approximately centered on local transit. A sequence of 10 consecutive images reveals continuous changes in the asteroid's profile and apparent shape, in good agreement with the sky projection of the three-dimensional model of the Database of Asteroid Models from Inversion Techniques. We measure a geometric mean diameter of 259 4 km, in good agreement with past estimates from a variety of techniques and wavelengths. Due to the viewing angle and inclination of the rotational pole, the southern hemisphere dominates all of the images. The median peak brightness temperature is 215 13 K, while the median over the whole surface is 197 15 K. With the unprecedented resolution of ALMA, we find that the brightness temperature varies across the surface with higher values correlated to the subsolar point and afternoon areas and lower values beyond the evening terminator. The dominance of the subsolar point is accentuated in the final four images, suggesting a reduction in the thermal inertia of the regolith at the corresponding longitudes, which are possibly correlated to the location of the putative large impact crater. These results demonstrate ALMA's potential to resolve thermal emission from the surface of main belt asteroids and to measure accurately their position, geometric shape, rotational period, and soil characteristics.
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