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

Arnal, Edmundo Marcelo

May, J.

Minniti, D.

Romero, Gisela Andrea

English

LAReferencia - Red Federada de Repositorios Institucionales de Publicaciones Científicas Latinoamericanas

The Cool Universe: Observing Cosmic DawnASP Conference Series, Vol. 344, 2005Chris Lidman and Danielle Alloin, eds.The AraOB1 Association and its Molecular ComplexE. M. ArnalInstituto Argentino de Radioastronomı́a, C.C. 5, Villa Elisa 1894,Argentina and Facultad de Cs. Astronómicas y Geof́ısicas, UNLP,Paseo del Bosque S/N, 1900, La Plata, ArgentinaG. A. RomeroInstituto Argentino de Radioastronomı́a, C.C. 5, Villa Elisa 1894,ArgentinaJ. MayDepartamento de Astronomı́a, Universidad de Chile, Casilla 36-D,Santiago, ChileD. MinnitiDepartment of Astronomy, Pontificia Universidad Católica, Casilla 306,Santiago 22, ChileAbstract. The results of low (HPBW1=8.′7) and intermediate (HPBW=2.′7)angular resolution carbon monoxide (12CO J= 1 → 0) line observations towardthe OB association AraOB1 are reported. The molecular features that arelikely to be associated with the OB-association span a velocity range from -28to -20 km s−1. The most negative radial velocities are observed along NGC6188(also known as the Rim Nebula). The main CO structures, labeled E and Fin Fig. 2, have radial velocities of about -23.5 and -21.8 km s−1, respectively.The former harbors the IRAS source IRAS16362−4845 and the infrared clus-ter RCW108-IR. The observations at intermediate resolution show noticeablechanges in shape, peak intensity and full width at half maximum in the line pro-files 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 withits surrounding molecular gas. A scale down version of this phenomenon is alsofound toward structure F. The total amount of molecular gas related to struc-tures E and F in NGC6188 is about 8.2×103 M⊙.IntroductionAraOB1 is an OB association in the southern sky (l=336.◦5, b=-1.◦5). It hasan age of ∼ 5×106 yr (Whiteoak 1963) and covers an area of ∼ 1 square degreearound its central cluster NGC6193. The most massive members of this clus-ter, the stars HD150135 and HD150136, are the main ionizing sources of thelow surface brightness optical emission nebula RCW108 (Rodgers, Campbell &1Half Power Beam Width173174 Arnal et al.Whiteoak 1960). About 15′ westwards of these stars, we find the Rim Nebula(also known as NGC6188), which marks the interface between RCW108 anda nearby dense dark nebula. Herbst & Havlen (1977) derived a distance of1320±120 pc to this cluster (see Arnal, May & Romero 2003, for a brief discus-sion).The average barycentric radial velocity2 of NGC6193 is −30.0 ± 2.8 km s−1(Arnal et al. 1988), while the radial velocity of RCW108 is about −20 km s−1(Georgelin & Georgelin 1970; Cersósimo 1982; Georgelin et al. 1996).Westwards of NGC6193, embedded in a dark cloud, there is an R associationcalled AraR1 (Herbst 1975), a bright optical knot (Frogel & Persson 1974) anda compact young infrared cluster (RCW108-IR) (Straw et al 1987).High resolution radio continuum observations at 5GHz (Goss & Shaver 1970)detected a small, high emission measure compact H ii region that might be pow-ered by an O8-O9 main sequence star (Urquhart et al. 2004). Radio recombina-tion line observations of this source (Wilson et al. 1970; Caswell & Haynes 1987)provide a radial velocity of about −25 km s−1, which is in very good agreementwith single-pointing molecular line observations carried out toward RCW108-IR(see Arnal et al. 2003 and references therein). Recently, a small area (2′× 2′) cen-tred on IRAS 16362−4845 has been surveyed by Urquhart et al. (2004), whilsta more extended area (roughly a square region 20′ in size) covering NGC6193,part of NGC6188 and IRAS 16362−4845 has been studied by Comerón, Schnei-der & Russeil (2005). Arnal, May & Romero (2003) mapped a 2.◦75 × 3.◦00region around RCW108 at 8.′7 resolution in the 115GHz CO line.Herbst & Havlen (1977) suggested that the formation of AraOB1 may havebeen triggered by a supernova explosion, while Arnal et al. (1987) suggested thatNGC6193 was formed by the action of an expanding H i shell that is possiblygenerated by the winds of the massive stars in NGC6167.For the reader’s benefit and the sake of clarity the main optical constituentsand their relative locations are superimposed on a R-band MAMA image of theAraOB1 region (see Fig. 1)Observations and Data ReductionThe 12CO (J= 1 → 0) line observations were carried out with the 1.2m ColumbiaUniversity telescope at CTIO (November 1996) and the 4m NANTEN telescopeat LCO (May 2001). Data taken with the former (latter) have a resolution of8.′7 (2.′7), a velocity resolution of 0.26 (0.055) km s−1 and a RMS noise level of0.15 (0.35)K.ResultsUsing the data collected at CTIO and relying on morphological and kinemat-ical criteria, nine molecular concentrations were found to be associated withAraOB1. These features constitute what we call the AraOB1 molecular com-plex. Five of these structures are shown in Fig. 2. This figure shows the in-2All velocities in this paper are referred to the Local Standard of Rest (LSR)Molecular Gas and AraOB1 175GALACTIC LONG.337.00 336.00 335.00-1.00-2.00NGC  6193NGC  6167RCW 108−IRNGC  6188αδFigure 1. Gray scale MAMA R-band image of the AraOB1 region. Thediameters of the circles correspond to the optical diameters of the open clustersNGC6193 and NGC6167. The filled triangle within the circle defining thelocation of NGC6193 marks the region observed by Phillips et al. (1986). Theplus signs indicate the position of some members of AraR1 (Herbst 1975).Single-pointing molecular line observations were mostly taken at the positionof RCW 108-IR. An indication of the orientation of the equatorial coordinatesystem is provided by the arrows in the upper right corner.tegrated CO emission (contour lines) in the velocity range -27 to -23 km s−1overlaid on an Hα image (grey scale). Features B and D very likely trace themolecular gas related to NGC6188, whilst feature E marks the location of theinfrared cluster RCW108-IR. The IRAS point source IRAS 16362−4845 is thefar infrared counterpart of the infrared cluster discovered by Straw et al (1987).The IRAS source IRAS 16348−4849 is seen projected onto feature F. Their ra-dial velocities lie in the range -24 to -23.5 km s−1 . Their masses, ∼4000M⊙for E and ∼3000M⊙ for F, were derived using the relationship between the H2176 Arnal et al.column density (N(H2)) and the equivalent width of CO (WCO) given by Stronget al. (1988), namely (N(H2)/WCO)=(2.3±0.3)×1020 mol. cm−2.BDEFC+0.40.0−0.4−0.4+0.4 0.0Figure 2. Overlay of the integrated CO distribution (contours between -27and -23 km s−1) from the observations made at CTIO on an Hα image (greyscale). The ordinate and the abscissa are angular offsets (in degrees) from thereference position (α, δ)(1950.0)=(249.◦00, -48.◦46)The higher angular resolution of the NANTEN data allows us to study insome detail the kinematical behavior of individual CO features. Fig. 3 showsaverage carbon monoxide profiles obtained toward different regions of concen-tration E. The changes in shape, peak intensity and full-width at half maximumamong the different profiles of the same concentration are easily noticeable.The strongest (∼ 22 K) and broadest (∼7 km s−1) lines are observed towardIRAS16362−4845. The kinematics may reflect the interaction between the in-frared cluster RCW108-IR and its surrounding molecular gas.The NANTEN data also revealed a radial velocity gradient of -0.25 km s−1pc−1along NGC6188. The radial velocity decreases from north to south.Acknowledgments. This work was partially funded by Consejo Nacionalde Investigaciones Cient́ıficas y Técnicas (CONICET) of Argentina under ProjectPIP 4252/96 and by Fundación Antorchas of Argentina under Project 13622/10.Molecular Gas and AraOB1 177Figure 3. Representative sample of average CO profiles obtained towardsdifferent regions of feature E. The profile units are T∗Ain K (ordinate) andVLSR in km s−1 (abscissa).ReferencesArnal, E. M., Cersósimo, J. C., May, J., & Bronfman, L. 1987, A&A, 174, 78Arnal, E. M., Morrel, N. I., Garćıa, B., & Levato, O. H. 1988, PASP, 100, 1076Arnal, E. M., May, J. & Romero, G. A. 2003, A&A, 412, 431Caswell, J. L., & Haynes, R.F. 1987, A&A, 171, 261Cersósimo, J. C. 1982, ApJL, 22, 157Comerón, F., Schneider, N. & Russeil, D. 2005, A&A, in press (astro-ph/0412125)Frogel, J. A., & Persson, S. E. 1974, ApJ, 214, 725Georgelin, Y. P., & Georgelin, Y. M. 1970, A&A, 6, 349Georgelin, Y. M., Russeil, D., Marcelin, M., Amram, D., Georgelin, Y. P., Goldés, G.,le Coarer, E., & Morandini, M. 1996, A&AS, 120, 41Goss, W. M., & Shaver, P.A. 1970, Australian J. Phys., Ap. Suppl. 14, 1Herbst, W. 1975, AJ, 80, 212Herbst, W., & Havlen, R.J 1977, A&AS, 30, 279Phillips, J. P., de Vries, C. P., & de Graauw, T. 1986, A&AS, 65, 465Rodgers, A. W., Campbell, C. T., & Whiteoak, J.B. 1960, MNRAS 121, 103Straw, S., Hyland, A. R., Jones, T. J., Harvey, P. M., et al. 1987, ApJ, 314, 283Strong, A. W., Bloemen, J. B. G. M., Dame, T. M., Grenier, I.A., Hermsen, W., Lebrun,F., Nyman, L.-Å, Pollock, A. M. T., & Thaddeus, P. 1988, A&A, 207, 1Urquhart, J. S., Thompson, M. A., Morgan, L. K. & White, G. J. 2004, A&A, 428, 723Whiteoak, J. B. 1963, MNRAS, 125, 105178 Arnal et al.Wilson, T. L., Mezger, P. G., Gardner, F. F., & Milne, D. K. 1970, A&A, 6, 364E. Arnal (left) reading one of the posters.

The Ara OB1 Association and its molecular complex

CONICET Digital

The Cool Universe: Observing Cosmic DawnASP Conference Series, Vol. 344, 2005Chris Lidman and Danielle Alloin, eds.The AraOB1 Association and its Molecular ComplexE. M. ArnalInstituto Argentino de Radioastronomı´a, C.C. 5, Villa Elisa 1894,Argentina and Facultad de Cs. Astrono´micas y Geof´ısicas, UNLP,Paseo del Bosque S/N, 1900, La Plata, ArgentinaG. A. RomeroInstituto Argentino de Radioastronomı´a, C.C. 5, Villa Elisa 1894,ArgentinaJ. MayDepartamento de Astronomı´a, Universidad de Chile, Casilla 36-D,Santiago, ChileD. MinnitiDepartment of Astronomy, Pontificia Universidad Cato´lica, Casilla 306,Santiago 22, ChileAbstract. The results of low (HPBW1=8.′7) and intermediate (HPBW=2.′7)angular resolution carbon monoxide (12CO J= 1 → 0) line observations towardthe OB association AraOB1 are reported. The molecular features that arelikely to be associated with the OB-association span a velocity range from -28to -20 km s−1. The most negative radial velocities are observed along NGC6188(also known as the Rim Nebula). The main CO structures, labeled E and Fin Fig. 2, have radial velocities of about -23.5 and -21.8 km s−1, respectively.The former harbors the IRAS source IRAS16362−4845 and the infrared clus-ter RCW108-IR. The observations at intermediate resolution show noticeablechanges in shape, peak intensity and full width at half maximum in the line pro-files 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 withits surrounding molecular gas. A scale down version of this phenomenon is alsofound toward structure F. The total amount of molecular gas related to struc-tures E and F in NGC6188 is about 8.2×103 M⊙.IntroductionAraOB1 is an OB association in the southern sky (l=336.◦5, b=-1.◦5). It hasan age of ∼ 5×106 yr (Whiteoak 1963) and covers an area of ∼ 1 square degreearound its central cluster NGC6193. The most massive members of this clus-ter, the stars HD150135 and HD150136, are the main ionizing sources of thelow surface brightness optical emission nebula RCW108 (Rodgers, Campbell &1Half Power Beam Width173174 Arnal et al.Whiteoak 1960). About 15′ westwards of these stars, we find the Rim Nebula(also known as NGC6188), which marks the interface between RCW108 anda nearby dense dark nebula. Herbst & Havlen (1977) derived a distance of1320±120 pc to this cluster (see Arnal, May & Romero 2003, for a brief discus-sion).The average barycentric radial velocity2 of NGC6193 is −30.0 ± 2.8 km s−1(Arnal et al. 1988), while the radial velocity of RCW108 is about −20 km s−1(Georgelin & Georgelin 1970; Cerso´simo 1982; Georgelin et al. 1996).Westwards of NGC6193, embedded in a dark cloud, there is an R associationcalled AraR1 (Herbst 1975), a bright optical knot (Frogel & Persson 1974) anda compact young infrared cluster (RCW108-IR) (Straw et al 1987).High resolution radio continuum observations at 5GHz (Goss & Shaver 1970)detected a small, high emission measure compact H ii region that might be pow-ered by an O8-O9 main sequence star (Urquhart et al. 2004). Radio recombina-tion line observations of this source (Wilson et al. 1970; Caswell & Haynes 1987)provide a radial velocity of about −25 km s−1, which is in very good agreementwith single-pointing molecular line observations carried out toward RCW108-IR(see Arnal et al. 2003 and references therein). Recently, a small area (2′× 2′) cen-tred on IRAS 16362−4845 has been surveyed by Urquhart et al. (2004), whilsta more extended area (roughly a square region 20′ in size) covering NGC6193,part of NGC6188 and IRAS 16362−4845 has been studied by Comero´n, Schnei-der & Russeil (2005). Arnal, May & Romero (2003) mapped a 2.◦75 × 3.◦00region around RCW108 at 8.′7 resolution in the 115GHz CO line.Herbst & Havlen (1977) suggested that the formation of AraOB1 may havebeen triggered by a supernova explosion, while Arnal et al. (1987) suggested thatNGC6193 was formed by the action of an expanding H i shell that is possiblygenerated by the winds of the massive stars in NGC6167.For the reader’s benefit and the sake of clarity the main optical constituentsand their relative locations are superimposed on a R-band MAMA image of theAraOB1 region (see Fig. 1)Observations and Data ReductionThe 12CO (J= 1→ 0) line observations were carried out with the 1.2m ColumbiaUniversity telescope at CTIO (November 1996) and the 4m NANTEN telescopeat LCO (May 2001). Data taken with the former (latter) have a resolution of8.′7 (2.′7), a velocity resolution of 0.26 (0.055) km s−1 and a RMS noise level of0.15 (0.35)K.ResultsUsing the data collected at CTIO and relying on morphological and kinemat-ical criteria, nine molecular concentrations were found to be associated withAraOB1. These features constitute what we call the AraOB1 molecular com-plex. Five of these structures are shown in Fig. 2. This figure shows the in-2All velocities in this paper are referred to the Local Standard of Rest (LSR)Molecular Gas and AraOB1 175GALACTIC LONG.337.00 336.00 335.00-1.00-2.00NGC  6193NGC  6167RCW 108−IRNGC  6188αδFigure 1. Gray scale MAMA R-band image of the AraOB1 region. Thediameters of the circles correspond to the optical diameters of the open clustersNGC6193 and NGC6167. The filled triangle within the circle defining thelocation of NGC6193 marks the region observed by Phillips et al. (1986). Theplus signs indicate the position of some members of AraR1 (Herbst 1975).Single-pointing molecular line observations were mostly taken at the positionof RCW 108-IR. An indication of the orientation of the equatorial coordinatesystem is provided by the arrows in the upper right corner.tegrated CO emission (contour lines) in the velocity range -27 to -23 km s−1overlaid on an Hα image (grey scale). Features B and D very likely trace themolecular gas related to NGC6188, whilst feature E marks the location of theinfrared cluster RCW108-IR. The IRAS point source IRAS 16362−4845 is thefar infrared counterpart of the infrared cluster discovered by Straw et al (1987).The IRAS source IRAS 16348−4849 is seen projected onto feature F. Their ra-dial velocities lie in the range -24 to -23.5 km s−1 . Their masses, ∼4000M⊙for E and ∼3000M⊙ for F, were derived using the relationship between the H2176 Arnal et al.column density (N(H2)) and the equivalent width of CO (WCO) given by Stronget al. (1988), namely (N(H2)/WCO)=(2.3±0.3)×1020 mol. cm−2.BDEFC+0.40.0−0.4−0.4+0.4 0.0Figure 2. Overlay of the integrated CO distribution (contours between -27and -23 km s−1) from the observations made at CTIO on an Hα image (greyscale). The ordinate and the abscissa are angular offsets (in degrees) from thereference position (α, δ)(1950.0)=(249.◦00, -48.◦46)The higher angular resolution of the NANTEN data allows us to study insome detail the kinematical behavior of individual CO features. Fig. 3 showsaverage carbon monoxide profiles obtained toward different regions of concen-tration E. The changes in shape, peak intensity and full-width at half maximumamong the different profiles of the same concentration are easily noticeable.The strongest (∼ 22 K) and broadest (∼7 km s−1) lines are observed towardIRAS16362−4845. The kinematics may reflect the interaction between the in-frared cluster RCW108-IR and its surrounding molecular gas.The NANTEN data also revealed a radial velocity gradient of -0.25 km s−1pc−1along NGC6188. The radial velocity decreases from north to south.Acknowledgments. This work was partially funded by Consejo Nacionalde Investigaciones Cient´ıficas y Te´cnicas (CONICET) of Argentina under ProjectPIP 4252/96 and by Fundacio´n Antorchas of Argentina under Project 13622/10.Molecular Gas and AraOB1 177Figure 3. Representative sample of average CO profiles obtained towardsdifferent regions of feature E. The profile units are T∗Ain K (ordinate) andVLSR in km s−1 (abscissa).ReferencesArnal, E. M., Cerso´simo, J. C., May, J., & Bronfman, L. 1987, A&A, 174, 78Arnal, E. M., Morrel, N. I., Garc´ıa, B., & Levato, O. H. 1988, PASP, 100, 1076Arnal, E. M., May, J. & Romero, G. A. 2003, A&A, 412, 431Caswell, J. L., & Haynes, R.F. 1987, A&A, 171, 261Cerso´simo, J. C. 1982, ApJL, 22, 157Comero´n, F., Schneider, N. & Russeil, D. 2005, A&A, in press (astro-ph/0412125)Frogel, J. A., & Persson, S. E. 1974, ApJ, 214, 725Georgelin, Y. P., & Georgelin, Y. M. 1970, A&A, 6, 349Georgelin, Y. M., Russeil, D., Marcelin, M., Amram, D., Georgelin, Y. P., Golde´s, G.,le Coarer, E., & Morandini, M. 1996, A&AS, 120, 41Goss, W. M., & Shaver, P.A. 1970, Australian J. Phys., Ap. Suppl. 14, 1Herbst, W. 1975, AJ, 80, 212Herbst, W., & Havlen, R.J 1977, A&AS, 30, 279Phillips, J. P., de Vries, C. P., & de Graauw, T. 1986, A&AS, 65, 465Rodgers, A. W., Campbell, C. T., & Whiteoak, J.B. 1960, MNRAS 121, 103Straw, S., Hyland, A. R., Jones, T. J., Harvey, P. M., et al. 1987, ApJ, 314, 283Strong, A. W., Bloemen, J. B. G. M., Dame, T. M., Grenier, I.A., Hermsen, W., Lebrun,F., Nyman, L.-A˚, Pollock, A. M. T., & Thaddeus, P. 1988, A&A, 207, 1Urquhart, J. S., Thompson, M. A., Morgan, L. K. & White, G. J. 2004, A&A, 428, 723Whiteoak, J. B. 1963, MNRAS, 125, 105178 Arnal et al.Wilson, T. L., Mezger, P. G., Gardner, F. F., & Milne, D. K. 1970, A&A, 6, 364E. Arnal (left) reading one of the posters.

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The Ara OB1 Association and its molecular complex

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