The molecular gas associated with the Association Ara OB1

E.M.Arnal 1,2, G.A.Romero3, J.May4,D.Minniti 5

1) Instituto Argentino de Radioastronomía, Argentina2) Universidad Nacional de La Plata, FCAG, Argentina3) Fellow from CONICET, Argentina4) Universidad de Chile, Depto de Astronomía, Chile5) Pontificia Universidad de Chile, Depto. Astronomía, Chile

objetos

Overview of the Ara OB1 regionNGC 6167 (l,b)= (335.2, -1.4)Distance = 1280± 180 pcAge (1,2)~(4-5) x 107 yrVrad~ -36± 14 kms-1

Earliest Sp.Type =>B3VAv~2.8±0.3 mag

NGC 6193(l,b)=(336.7, -1.6)1100 < d < 1340 pcDistance = 1320± 120 pcAge ~5 x 106 yrVrad~ -30.6± 6.3 kms-1

Av~1.5 magHD 150135 (O7V)HD 150136 (O5V: + O6:)

NGC 6188=> The Rim nebula

335.0336.0337.0

-2.0

-1.0

Galactic Longitude

Gal

acti

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atit

ude

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).

NGC 6167 NGC 6193 RCW108-IR

Ara OB1: another example of sequential star forming ?

NGC6193

RCW108RCW108-IR

15´ ~ 5.8pc

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)

-26.9 (CO) < Vr < -22.4 (H2CO) kms-Vr(H92α)=-24 kms-

1(ATCA,HPBW=20”)

Vr(st) ~ -30.6±6.3 kms-1

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 withbright 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

The region of Ara OB1 is an active high mass star forming region in the southern sky.

Very little is known about the large scale spatialdistribution and properties of the molecular gas

that may be physically related to this stellar complex.

Based on above...

And...

Carbon Monoxide databases12CO (J=1 => 0), 0 = 115.271 GHz

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 0.055Vel. Cov. (kms-1) ~66 ~112Observing shift Nov. 1996 April – May 2001

Integrated CO emission between –30 and –15 kms-1

Galactic Longitude

Gala

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ati

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e -1.0

-2.0

335.0336.0337.0

CTIO results

(FWHM=8’.7)

Ta*

Galactic Longitude

Gala

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ati

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335.0336.0337.0

-1.0

-2.0

CO channel images

-28.0 -25.9 -23.8

-21.7 -19.6 -17.5

Channel width= 2.1 kms-1

B

D

E F

C

-24

-24.6

-23.5-21.8

-23.8

CTIO results [-27,-23]kms-1 (Arnal et al. 2003)

Declin

ati

on

-48 00

-49 00

20

40

16h39m 16h33mRight Ascension

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

Composite image

12CO (λ~ 2.6mm)

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

Features E, F & C (NANTEN)

[-28,-18] kms-1 [-27,-19] kms-1

Right ascension Right ascension

Declin

ati

on

2*

1

( )v

-1CO a

v

W T v dv [K Kms ]

E F C

NGC 6188 (The Rim nebula) and Features E, F & C (NANTEN)

-25.2

-23.8

-25-25.7

-26.3

-27

-26.3

-24.2

-26

-23.7

-23.4

-23.3

-21.4

-22

-23.7

-29

F

C

E

NGC 6188 – Position-velocity

Velocity gradients along NGC 6188

-36 –32 –28 -24 [Kms-1]

NGC6188D

eclin

ati

on

RAD

eclin

ati

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RCW 108_IRdeclin

ati

on

IRAS 16362-4845

Velocity vs position diagram for feature E (NANTEN data)

S12= 208 JyS25= 2980 JyS60= 12200 JyS100=18700 Jy

-48 15

30

45

-49 00

-30 -26 -22 -18 14 Vel (kms-1)

Velocity vs position diagram for feature F (NANTEN data)

Rad. Vel. (kms-1)

Declin

ati

on IRAS 16348-4849

S12= 2.7 JyS25= 17.1 JyS60= 356 JyS100=4080 Jy -28 -24 -20

-48 40

-49 00

Ta*

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) velocitiesThe 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 ...

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?))

Acknowledgements

Dr. M. Roth, Director of Las Campanas ObservatoryProf. Y. Fukui and Dr. A. Mizuno for allocating observing time to this projectNANTEN crew during the observing shift: Dr. Toshikazu Onishi, and Yoshiaki Moriguchi and Hiro Saito.

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

Composite image

12CO (λ~ 2.6mm)

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

-1.00

-2.00

-3.00

Gala

cti

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Lati

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337.0 336.0 335.0 334.0 Galactic Longitude

Continuum emission at 2.417 GHz (HPBW=10’ )

S2.41 (Jy)

CTIO & NANTEN[-27,-23] kms-1

Right ascension

Declin

ati

on

IRAS point sources

Yamaguchi et al 1999 (Y)

Arnal et al 2003 (J)

337.0 336.0 335.0

-1.00

-2.00

Gala

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Galactic Longitude