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The molecular gas associated with the Association Ara OB1

The molecular gas associated with the Association Ara OB1. E.M.Arnal 1,2 , G.A.Romero 3 , J.May 4 , D.Minniti 5. Instituto Argentino de Radioastronomía, Argentina Universidad Nacional de La Plata, FCAG, Argentina Fellow from CONICET, Argentina

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The molecular gas associated with the Association Ara OB1

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  1. The molecular gas associated with the Association Ara OB1 E.M.Arnal 1,2, G.A.Romero3, J.May4, D.Minniti 5 • Instituto Argentino de Radioastronomía, Argentina • Universidad Nacional de La Plata, FCAG, Argentina • Fellow from CONICET, Argentina • Universidad de Chile, Depto de Astronomía, Chile • Pontificia Universidad de Chile, Depto. Astronomía, Chile

  2. Overview of the Ara OB1 region NGC 6167 (l,b)= (335.2, -1.4) Distance = 1280± 180 pc Age (1,2)~(4-5) x 107 yr Vrad~ -36± 14 kms-1 Earliest Sp.Type =>B3V Av~2.8±0.3 mag objetos -1.0 NGC 6193 (l,b)=(336.7, -1.6) 1100 < d < 1340 pc Distance = 1320± 120 pc Age ~5 x 106 yr Vrad~ -30.6± 6.3 kms-1 Av~1.5 mag HD 150135 (O7V) HD 150136 (O5V: + O6:) Galactic Latitude -2.0 NGC 6188=> The Rim nebula 337.0 335.0 336.0 Galactic Longitude

  3. Ara OB1: another example of sequential star forming ? • Herbst & Havlen (1977) have suggested that the star formation in Ara OB1 may may have been triggered by a supernova explosion. • Arnal et al. (1988) have found evidence for an expanding shell of neutral (HI) and molecular (CO) gas coexisting with the OB association.It is suggested that this thick shell, possibly originated by the winds from the massive stars of NGC6167, is genetically linked to AraOB1. • Rizzo & Bajaja (1994) also found evidence for an expanding HI structure in the region. • A multicolor polarimetric study of the region (Waldhausen et al., 1999) is also in line with the scenario of sequential star formation suggested by Arnal et al. (1988). RCW108-IR NGC 6167 NGC 6193

  4. RCW108-IR RCW108 -26.9 (CO) < Vr < -22.4 (H2CO) kms-Vr(H92α)=-24 kms-1(ATCA,HPBW=20”) Vr(Hα)=-18.9±6.2 kms-1 Vr(H109α)= -24.9±2.2 kms-1 (HPBW=4’.4) Vr(H166α)= -20.0±5.0 kms-1 (HPBW=34’.4) NGC6193 15´ ~ 5.8pc Vr(st) ~ -30.6±6.3 kms-1

  5. Previous radio continuum and molecular line observations in the region Molecular line • Mostly towards RCW108-IR. • OH 1.667 GHz (Caswell & Robinson 1967, HPBW=12’, Vr= -24.0 kms-1) • H2CO (4.8 GHz) (Whiteoak & Gardner 1974, HPBW=4’.2, Vr= -22.4 kms-1) • CO (115 GHz) (Gillespie et al. 1977, HPBW= ) • CO (115 GHz) (Whiteoak & Otrupcek 1982, HPBW=2’.8, Vr = -26.5 kms-1 • 12CO,13CO,18CO of a small region (2’x 2’) centred on RCW108-IR, HPBW=30”(±10”), Vr=-22.5 / -25.1 kms-1. (Urquhart et al. 2003) [MOPRA] Extensive 13CO (110 GHz) of this region were performed by Yamaguchi et al. (1999) , as part of their molecular line studies of southern sky HII region “associated with bright rimmed clouds”. Association of IRAS point sources with molecular clouds.[Nanten] Radio Continuum • High resolution (HPBW=5’) 5 GHz Parkes (Goss & Shaver 1970) [Sυ= 8.6 Jy] • 2.4 GHz Parkes (Duncan et al. 1995) (HPBW=10’) [Sυ=9.2±0.6 Jy] • Interferometric observations at 408 MHz (Shaver & Goss 1970) [Sυ= 2.2 Jy] • ATCA 4.8 (HPBW=20”) & 8.3 (HPBW=12”) GHz. Embedded source is a O8-O9 star

  6. Based on above... The region of Ara OB1 is an active high mass star forming region in the southern sky. And... Very little is known about the large scale spatial distribution and properties of the molecular gas that may be physically related to this stellar complex.

  7. Radiotelescope 1.2-m 4m Columbia University - CTIO NANTEN - Las Campanas Covered area 2o.75 x 3o 0o.8 x 0º.4 & 0º.5 x 0º.6 HPBW (arcmin) 8.7 2.7 Spatial sampling 7.5 1.35 & 2.7 Vel. Res. (kms-1) 0.26 0.055 Vel. Cov. (kms-1) ~66 ~112 Observing shift Nov. 1996 April – May 2001 Carbon Monoxide databases 12CO (J=1 => 0), n0 = 115.271 GHz

  8. Integrated CO emission between –30 and –15 kms-1 Ta* -1.0 CTIO results Galactic Latitude (FWHM=8’.7) -2.0 337.0 336.0 335.0 Galactic Longitude

  9. CO channel images Channel width= 2.1 kms-1 -1.0 -2.0 -28.0 -25.9 -23.8 337.0 336.0 335.0 Galactic Latitude -21.7 -19.6 -17.5 Galactic Longitude

  10. B -24 D -24.6 -23.8 C E F -23.5 -21.8 [-27,-23]kms-1 (Arnal et al. 2003) CTIO results -48 00 20 Declination 40 -49 00 16h33m 16h39m Right Ascension

  11. Ara OB1 (l,b)=(336o.5,-1o.5) 12CO(λ~ 2.6mm) Composite image Red ([SII] 6716,6731), Green (Hα), Blue([OIII])

  12. Features E, F & C (NANTEN) Declination F C E Right ascension Right ascension [-28,-18] kms-1 [-27,-19] kms-1

  13. -23.7 -21.4 -22 NGC 6188 (The Rim nebula) and Features E, F & C (NANTEN) -24.2 -25.2 -23.8 -25 -25.7 -26 -26.3 -26.3 -23.3 E -23.4 -27 C -29 -23.7 F

  14. -36 –32 –28 -24 [Kms-1] NGC 6188 – Position-velocity NGC6188 Declination Declination RA Velocity gradients along NGC 6188

  15. Velocity vs position diagram for feature E (NANTEN data) -48 15 declination 30 45 RCW 108_IR IRAS 16362-4845 S12= 208 Jy S25= 2980 Jy S60= 12200 Jy S100=18700 Jy -49 00 Vel (kms-1) -30 -26 -22 -18 14

  16. Velocity vs position diagram for feature F (NANTEN data) Ta* -48 40 IRAS 16348-4849 Declination S12= 2.7 Jy S25= 17.1 Jy S60= 356 Jy S100=4080 Jy -49 00 -28 -24 -20 Rad. Vel. (kms-1)

  17. Summing up • Based on morphological and kinematical arguments, nine molecular concentrations are likely to be associated with the absorbing material observed in the vicinity of NGC 6193 • Most of the CO structures associated with Ara OB1 fall in the narrow velocity range –24 to –20 kms-1.But... There is also CO gas (projected close to NGC 6193) that depicts the highest negative (-28.5 kms-1) and positive (-17.5 kms-1) velocities • The total amount of molecular gas is ~ 1.5 x 104 Mо. • Three concentrations (labeled E, F and H, respectively) are the dominant features. • The above features have a strong correlation with infrared emission (IRAS+MSX) • Peak of emission of feature E almost coincident with RCW108-IR (IRAS16362-4845) • Velocity gradient along NGC 6188. On average, its radial velocity is a few kms-1 more negative than those of structures C, E, F & H. • Possible molecular outflows in features E and F?

  18. Coming soon ... • Infrared spectroscopy of the open cluster associated with IRAS 1632-4845 (R.Barbá) • Revisiting the HI ( Parkes λ~21-cm) N. McClure-Griffiths. • Narrow band filter images ==> Ionization structure (R. Barbá + F. Comeron) • New molecular line observations (Structures C, E, F, H plus NGC 6188 (PDR edge-on?))

  19. Acknowledgements • Dr. M. Roth, Director of Las Campanas Observatory • Prof. Y. Fukui and Dr. A. Mizuno for allocating observing time to this project • NANTEN crew during the observing shift: Dr. Toshikazu Onishi, and Yoshiaki Moriguchi and Hiro Saito.

  20. Ara OB1 (l,b)=(336o.5,-1o.5) 12CO(λ~ 2.6mm) Composite image Red ([SII] 6716,6731), Green (Hα), Blue([OIII])

  21. Continuum emission at 2.417 GHz (HPBW=10’ ) S2.41 (Jy) -1.00 Galactic Latitude -2.00 -3.00 337.0 336.0 335.0 334.0 Galactic Longitude

  22. CTIO & NANTEN[-27,-23] kms-1 Declination Right ascension

  23. IRAS point sources -1.00 Galactic Latitude -2.00 337.0 336.0 335.0 Galactic Longitude Yamaguchi et al 1999 (Y) Arnal et al 2003 (J)

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