We analyze the distribution of the molecular gas and the dust in the molecular clump linked to IRAS 10361-5830, located in the environs of the bubble-shaped HII region Gum 31 in the Carina region, with the aim of determining the main parameters of th
e associated material and investigating the evolutionary state of the young stellar objects identified there. Using the APEX telescope, we mapped the molecular emission in the J=3-2 transition of three CO isotopologues, 12CO, 13CO and C18O, over a 1.5 x 1.5 region around the IRAS position. We also observed the high density tracers CS and HCO+ toward the source. The cold dust distribution was analyzed using submillimeter continuum data at 870 mu obtained with the APEX telescope. Complementary IR and radio data at different wavelengths were used to complete the study of the ISM. The molecular gas distribution reveals a cavity and a shell-like structure of ~ 0.32 pc in radius centered at the position of the IRAS source, with some young stellar objects (YSOs) projected onto the cavity. The total molecular mass in the shell and the mean H$_2$ volume density are ~ 40 solar masses and ~(1-2) x 10$^3$ cm$^{-3}$, respectively. The cold dust counterpart of the molecular shell has been detected in the far-IR at 870 mu and in Herschel data at 350 mu. Weak extended emission at 24 mu from warm dust is projected onto the cavity, as well as weak radio continuum emission. A comparison of the distribution of cold and warm dust, and molecular and ionized gas allows us to conclude that a compact HII region has developed in the molecular clump, indicating that this is an area of recent massive star formation. Probable exciting sources capable of creating the compact HII region are investigated. The 2MASS source 10380461-5846233 (MSX G286.3773-00.2563) seems to be responsible for the formation of the HII region.
With the aim of investigating the presence of molecular and dust clumps linked to two star forming regions identified in the expanding molecular envelope of the stellar wind bubble RCW78, we analyzed the distribution of the molecular gas and cold dus
t. To accomplish this study we performed dust continuum observations at 870 mu m and 13CO(2-1) line observations with the APEX telescope, using LABOCA and SHeFI-1 instruments, respectively, and analyzed Herschel images at 70, 160, 250, 350, and 500 mu m. These observations allowed us to identify cold dust clumps linked to region B (named the Southern clump) and region C (clumps 1 and 2) and an elongated Filament. Molecular gas was clearly detected linked to the Southern clump and the Filament. The velocity of the molecular gas is compatible with the location of the dense gas in the expanding envelope of RCW78. We estimate dust temperatures and total masses for the dust condensations from the emissions at different wavelengths in the far-IR and from the molecular line using LTE and the virial theorem. Masses obtained through different methods agree within a factor of 2-6. CC-diagrams and SED analysis of young stellar objects confirmed the presence of intermediate and low mass YSOs in the dust regions, indicating that moderate star formation is present. In particular, a cluster of IR sources was identified inside the Southern clump. The IRAC image at 8 mu m revealed the existence of an infrared dust bubble of 16 arcsec in radius probably linked to the O-type star HD117797 located at 4 kpc. The distribution of the near and mid infrared emission indicate that warm dust is associated with the bubble.
We present a study of the ionized, neutral atomic, and molecular gas associated with the ring nebula RCW 78 around the WR star HD 117688 (= WR 55). We based our study on CO observations carried out with the SEST and NANTEN telescopes. We report the d
etection of molecular gas with velocities in the range -56 to -33 km/s. The CO emission is mainly connected to the western section, with a total molecular mass of 1.3 x 10^5 solar masses. The analysis of the HI gas distribution reveals the HI envelope of the molecular cloud, while the radio continuum emission shows a ring-like structure, which is the radio counterpart of the optical nebula. The gas distribution is compatible with the western section of RCW 78 having originated in the photodissociation and ionization of the molecular gas by HD 117688, and with the action of the stellar winds of the WR star. A number of infrared point sources classified as YSO candidates showed that stellar formation activity is present in the molecular gas linked to the nebula. The fact that the expansion of the bubble have triggered star formation in this region can not be discarded.
In our search for interstellar bubbles around massive stars we analyze the environs of the O-type stars HD 38666, HD 124979, HD 163758, and HD 171589. The location of the stars, which are placed far from the galactic plane, favors the formation of la
rge wind bubbles. We investigate the distribution of the neutral and ionized gas based on HI, CO, and radio continuum data, and that of the interstellar dust based on far infrared IRIS images. Here we report the discovery of neutral gas cavities and slowly expanding shells associated with the four massive stars. IR and optical counterparts were also detected for some of the stars. We discuss the probability that the features have originated in the action of the stellar winds on the surrounding gas.
We present a study of the HII region Sh2-205 and its environs, based on data obtained from the CGPS, 12CO observations, and MSX data. We find that Sh2-205 can be separated in three independent optical structures: SH 149.25-0.0, SH 148.83-0.67, and LB
N 148.11-0.45. The derived spectral indices show the thermal nature of SH 148.83-0.67 and LBN 148.11-0.45. The morphology of SH 148.83-0.67, both in the optical and radio data, along with the energetic requ irements indicate that this feature is an interstellar bubble powered by the UV photons of HD 24431 (O9 III). LBN 148.11-0.45 has the morphology of a classic al HII region and their ionizing sources remain uncertain. Dust and molecular gas are found related to LBN 148.11-0.45.Particularly, a photodissociation region is detected at the interface between the ionized and molecular regions. If the proposed exciting star HD 24094 were an O8--O9 type star, as suggested by its near-infrared colors, its UV photon flux would be enough to explain the ionization of the nebula. The optical, radio continuum, and 21-cm line data allow us to conclude that SH 148.83-0.67 is an interstellar bubble powered by the energetic action of HD 24431. The associated neutral atomic and ionized masses are 180 Mo and 300 Mo, respectively. The emission of SH 149.25-0.0 is too faint to derive the dust and gas parameters. An HI shell centered at (l,b) = (149.0, 1.5) was also identified. It correlates morphologically with molecular gas emission. The neutral atomic and molecular masses are 1600 Mo and 2.6 x 10^4 Mo, respectively. The open cluster NGC 1444 is the most probable responsible for shaping this HI structure.
