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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
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
objetos

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

slide3

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

slide4

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

slide5

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
slide6

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.

carbon monoxide databases

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

slide8

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

slide9

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

ctio results

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

slide11

Ara OB1 (l,b)=(336o.5,-1o.5)

12CO(λ~ 2.6mm)

Composite image

Red ([SII] 6716,6731), Green (Hα), Blue([OIII])

features e f c nanten
Features E, F & C (NANTEN)

Declination

F

C

E

Right ascension

Right ascension

[-28,-18] kms-1

[-27,-19] kms-1

ngc 6188 the rim nebula and features e f c nanten

-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

ngc 6188 position velocity

-36 –32 –28 -24

[Kms-1]

NGC 6188 – Position-velocity

NGC6188

Declination

Declination

RA

Velocity gradients along NGC 6188

slide15

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

slide16

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)

summing up
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?
coming soon
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?))

slide19

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.

slide20

Ara OB1 (l,b)=(336o.5,-1o.5)

12CO(λ~ 2.6mm)

Composite image

Red ([SII] 6716,6731), Green (Hα), Blue([OIII])

slide21

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

ctio nanten 27 23 k m s 1
CTIO & NANTEN[-27,-23] kms-1

Declination

Right ascension

slide23

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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