A 12CO (J = 1 -> 0) study towards the Ara OB1 region

Intermediate angular resolution (HPBW = 8. 0 7) carbon monoxide (12CO J = 1→0) line observations towards the OB association Ara OB1 are reported. The molecular line observations cover an area of 2. ◦75 × 3. ◦00, and disclose a rich and complex distribution of the molecular line emission. The molecular features likely to be associated with the OB-association Ara OB1 span the velocity range from −28 to −20 km s−1. The most negative radial velocities are observed along NGC 6188 (≡Rim nebula). This nebula marks the interface between the H region RCW 108 and the highly absorbing molecular material located westwards of the ionised region. The dominant CO structures, labeled E and F, have a radial velocity of about −23.5 and −21.8 km s−1, respectively. The former harbours a bright optical knot, the infrared cluster RCW-108 and the strong IRAS source 16362−4845. IRAS point sources are also seen in projection onto 12CO concentrations F and H. This may indicate that the star forming process is a widespread phenomenon in this molecular complex. Extended continuum emission, having a high degree of spatial correlation with both the infrared and molecular emission, is observed in the region. We believe that this emission, thermal in nature, arises from the ionised surface layers of the molecular complex. The ionising agents are the high mass stars of NGC 6193, the nucleus of Ara OB1. The total amount of molecular gas related to Ara OB1 is about ∼1.4×104 M .Fil: Arnal, Edmundo Marcelo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: May, J.. Universidad de Chile; ChileFil: Romero, Gisela Andrea. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentin

Sh2-205 - I: the surrounding interstellar medium

We investigate the distribution of the interstellar matter in the environs of the H II region Sh2-205, based on neutral hydrogen 21-cm-line data and radio continuum images at 408 and 1420 MHz obtained from the CGPS, 12CO (J=1 →0) observations, high-resolution IRAS data (HIRES), and MSX data. Sh2-205 can be separated into three distinct optical structures: SH 149.25-0.0, SH 148.83-0.67, and LBN 148.11-0.45. The three regions are detected at both 408 and 1420 MHz. The derived spectral indices show the thermal nature of SH 148.83-0.67 and LBN 148.11-0.45. LBN 148.11-0.45 is a classical H II region surrounded by an H i shell. The associated neutral atomic and ionized masses are 65 M⊙ and 70 M⊙, respectively. Dust and molecular gas (∼6 × 104 M⊙) related to this ionized region have been found. In particular, 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 colours, its UV photon flux would be strong 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 M⊙ and 300 M⊙, respectively. The emission of SH 149.25-0.0 is too faint to derive the dust and gas parameters. An H I shell centred at (l, b) = (149°0', -1°30') was also identified. It correlates morphologically with the molecular gas emission. The neutral atomic and molecular masses of the shell are 1600 M⊙ and 2.6 × 104 M⊙, respectively. The open cluster NGC 1444 is probably responsible for shaping this H I structure.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Sh2-205 - II. Quiescent star-formation activity

We present a study of active star-forming regions in the environs of the H ii region Sh2-205. The analysis is based on data obtained from point source catalogues and images extracted from the Two-Micron All-Sky Survey (2MASS), Midcourse Space Experiment (MSX) and IRAS surveys. Complementary data are taken from a CO survey. The identification of primary candidates for star-formation activity is made following colour criteria and a correlation with molecular gas emission. A number of star-formation tracer candidates are projected on to two substructures of the H ii region: SH 148.83-0.67 and SH 149.25-0.00. However, the lack of molecular gas related to these structures casts doubt on the nature of the sources. Additional infrared sources may be associated with the H i shell centred at (l, b) = (149°0′, -1°30′). The most striking active area was found in connection with the H ii region LBN 148.11-0.45, where star-formation candidates are projected on to molecular gas. The analytical model of the 'collect and collapse' process shows that star-formation activity could have been triggered by the expansion of this H ii region.Facultad de Ciencias Astronómicas y Geofísica

Sh2-205 - II. Quiescent star-formation activity

We present a study of active star-forming regions in the environs of the H ii region Sh2-205. The analysis is based on data obtained from point source catalogues and images extracted from the Two-Micron All-Sky Survey (2MASS), Midcourse Space Experiment (MSX) and IRAS surveys. Complementary data are taken from a CO survey. The identification of primary candidates for star-formation activity is made following colour criteria and a correlation with molecular gas emission. A number of star-formation tracer candidates are projected on to two substructures of the H ii region: SH 148.83-0.67 and SH 149.25-0.00. However, the lack of molecular gas related to these structures casts doubt on the nature of the sources. Additional infrared sources may be associated with the H i shell centred at (l, b) = (149°0′, -1°30′). The most striking active area was found in connection with the H ii region LBN 148.11-0.45, where star-formation candidates are projected on to molecular gas. The analytical model of the 'collect and collapse' process shows that star-formation activity could have been triggered by the expansion of this H ii region.Facultad de Ciencias Astronómicas y Geofísica

Multiwavelength study of RCW 108 as a massive star forming region

NGC 6193 is an open cluster embedded in an HII region (RCW 108, Rodgers et al. 1960) located 15^´ eastwards of NGC 6188. The later is a bright rimmed cloud that stretches over 30^´ in the north-south direction, and marks the interface between RCW 108 and nearby dark clouds. RCW 108 is being powered by the multiple O-type star systems, namely HD 150135-HD 150136 (Niemela & Gamen 2005) in the core of NGC 6193. The UV photons emitted by these stars may drive photoinization-induced shocks into the nearby molecular clouds, possibly originating the well studied infrared cluster RCW 108-IR (Comerón et al. 2005, and references therein). In this work we describe the morphology of the distribution of the photoionized and shock-excited gas based on Hα, [O III] and [S II] images, ^{13}CO observations, and infrared data (2MASS, MSX).Fil: Romero, Gisela Andrea. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de la Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arnal, Edmundo Marcelo. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

Stellar formation in HI interstellar bubbles around massive stars

Stellar winds from O and WR stars transfer large amounts of mechanical energy and momentum into the interstellar medium. They sweep up and compress the interstellar material, creating interstellar bubbles. These structures are detected as optical ring nebulae, as thermal radio continuum sources, as infrared shells, as neutral gas voids and expanding shells in the HI line emission distribution, and as molecular shells.Facultad de Ciencias Astronómicas y Geofísica

Multiwavelength study of RCW 108 as a massive star forming region

NGC 6193 is an open cluster embedded in an Hii region (RCW 108, Rodgers et al. 1960) located 15 0 eastwards of NGC 6188. The later is a bright rimmed cloud that stretches over 30 0 in the north-south direction, and marks the interface between RCW 108 and nearby dark clouds. RCW 108 is being powered by the multiple O-type star systems, namely HD 150135-HD 150136 (Niemela & Gamen 2005) in the core of NGC 6193. The UV photons emitted by these stars may drive photoinization-induced shocks into the nearby molecular clouds, possibly originating the well studied infrared cluster RCW108- IR (Comerón et al. 2005, and references therein). In this work we describe the morphology of the distribution of the photoionized and shock-excited gas based on Hα, [O III] and [S II] images, 13CO observations, and infrared data (2MASS, MSX).Facultad de Ciencias Astronómicas y Geofísica

Millimeter and Far-IR observations of the IRDC G341.24-0.27

Infrared Dark Clouds (IRDCs) are the cold T 10^{5} cm^{-3}) regions, with a scale of 1 - 10 pc and a mass of 10× ^{2-5}M_o. Cores within the IRDCs may be in different phases, from a quiescent to an active one. Quiescent cores represent the earliest protostellar (starless) core phase without infrared signatures of star formation, commonly observed at far IR wavelengths, while active cores have extended and enhanced 4.5μm emission. In this work, we analyze CO(2-1), 13CO(2-1), and CO(2-1) lines, and mid- and far-infrared data towards the EGOS (Extended Green Objects) G341.23-0.27 and G341.22-0.26(a), projected onto the IRDC G341.24-0.27.Fil: Vasquez, Javier. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Cappa, Cristina Elisabeth. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Romero, Gisela Andrea. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Rubio, Mónica. Universidad de Chile; ChileXIV Latin American Regional IAU MeetingFlorianopolisBrasilInternational Astronomical Unio

The Ara OB1 Association and its molecular complex

Carbon monoxide (12CO J= 1 ?¨ 0) line observations toward the OB association Ara OB1 are reported. The molecular features that are likely to be associated with the OB-association span a velocity range from -28 to -20 km s-1. The most negative radial velocities are observed along NGC 6188 (also known as the Rim Nebula). The main CO structures, labeled E and F in Fig. ref{arnal:COobs}, have radial velocities of about -23.5 and -21.8 km s-1, respectively. The former harbors the IRAS source IRAS 16362-4845 and the infrared cluster RCW 108-IR. The observations at intermediate resolution show noticeable changes in shape, peak intensity and full width at half maximum in the line profiles observed toward structures E and F. The large line widths, about 7.5 km s-1, found toward structure E very likely reflect the interaction of RCW 108-IR with its surrounding molecular gas. A scale down version of this phenomenon is also found toward structure FFil: Arnal, Edmundo Marcelo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Romero, Gisela Andrea. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: May, J.. Universidad de Chile; ChileFil: Minniti, D.. Universidad Católica de Chile; Chil

Molecular gas related to the ring nebula RCW 78 around HD 117688

We investigate the distribution of the interstellar gas related to RCW 78 based on ^{12}CO(1-0) observations carried out with the SEST telescope and on data belonging to the NANTEN survey. Complementary HI 21-cm line data from the SGPS and radio data at 4.85 GHz were also used. We report the detection of molecular gas having velocities in the range [-56,-33] km/s associated with the western section of RCW 78. The CO emission distribution is compatible with the interpretation that the western section of the nebula originated in the photodissociation and ionization of the molecular gas by the UV photons of the WN7 star HD 117688, which, along with the action of the stellar winds, carved the molecular cloud.Investigamos la distribución del gas interestelar asociado a RCW 78 utilizando observaciones de 12CO(1-0) obtenidas con el telescopio SEST y datos pertenecientes al relevamiento de NANTEN. Se utilizan tambi´en datos complementarios de la línea de 21 cm del Hi extraídos del SGPS y del continuo de radio en 4.85 GHz. Reportamos la detección de gas molecular con velocidades en el intervalo [–56,–33] km s−1 asociado con el sector oeste de RCW 78. La distribución del CO es compatible con la interpretación de que la nebulosa se originó en la fotodisociación e ionización del gas molecular por los fotones ultravioletas de la estrella WN7 HD 117688, los cuales, junto con la acción de los vientos estelares, socavaron la nube molecular.Fil: Cappa, Cristina Elisabeth. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; ArgentinaFil: Rubio, Mónica. Universidad de Chile; ChileFil: Martin, Maria Cristina. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; ArgentinaFil: Romero, Gisela Andrea. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentin