2015A&A...575A..27T


C.D.S. - SIMBAD4 rel 1.7 - 2020.01.21CET06:35:28

2015A&A...575A..27T - Astronomy and Astrophysics, volume 575A, 27-27 (2015/3-1)

Star formation in Chamaeleon I and III: a molecular line study of the starless core population.

TSITALI A.E., BELLOCHE A., GARROD R.T., PARISE B. and MENTEN K.M.

Abstract (from CDS):

The Chamaeleon dark molecular clouds are excellent nearby targets for low-mass star formation studies. Even though they belong to the same cloud complex, Cha I and II are actively forming stars while Cha III shows no sign of ongoing star formation. We aim to determine the driving factors that have led to the very different levels of star formation activity in Cha I and III and examine the dynamical state and possible evolution of the starless cores within them. Observations were performed in various molecular transitions with the APEX and Mopra telescopes. We examine the kinematics of the starless cores in the clouds through a virial analysis, a search for contraction motions, and velocity gradients. The chemical differences in the two clouds are explored through their fractional molecular abundances, derived from a non-LTE analysis, and comparison to predictions of chemical models. Five cores are gravitationally bound in Cha I and one in Cha III. The so-called infall signature indicating contraction motions is seen toward 8-17 cores in Cha I and 2-5 cores in Cha III, which leads to a range of 13-28% of the cores in Cha I and 10-25% of the cores in Cha III that are contracting and may become prestellar. There is no significant difference in the turbulence level in the two clouds. Future dynamical interactions between the cores will not be dynamically significant in either Cha I or III, but the subregion Cha I North may experience collisions between cores within ∼0.7Myr. Turbulence dissipation in the cores of both clouds is seen in the high-density tracers N2H+ 1-0 and HC3N 10-9 which have lower non-thermal velocity dispersions compared to C17O 2-1, C18O 2-1, and C34S 2-1. Evidence of depletion in the Cha I core interiors is seen in the abundance distributions of the latter three molecules. The median fractional abundance of C18O is lower in Cha III than Cha I by a factor of ∼2. The median abundances of most molecules (except methanol) in the Cha III cores lie at the lower end of the values found in the Cha I cores. A difference in chemistry is thus seen. Chemical models suitable for the Cha I and III cores are used to constrain the effectiveness of the HC3N to N2H+ abundance ratio as an evolutionary indicator. Both contraction and static chemical models indicate that this ratio is a good evolutionary indicator in the prestellar phase for both gravitationally bound and unbound cores. In the framework of these models, we find that the cores in Cha III and the southern part of Cha I are in a similar evolutionary stage and are less chemically evolved than the central region of Cha I. The measured HC3N/N2H+ abundance ratio and the evidence for contraction motions seen towards the Cha III starless cores suggest that Cha III is younger than Cha I Centre and that some of its cores may form stars in the future if contraction does not cease. The cores in Cha I South may on the other hand be transient structures.

Abstract Copyright:

Journal keyword(s): stars: formation - ISM: kinematics and dynamics

Simbad objects: 31

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Number of rows : 31

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 2MASX J00404168+4038281 GlC 00 40 41.685 +40 38 28.16 19.99 19.04 17.89 16.91 16.14 ~ 37 0
2 Bol 68 GlC 00 42 03.2026147801 +40 58 50.143293337 18.140 17.600 16.24 15.590 14.840 ~ 48 0
3 NAME Per B1-E PoC 03 36 45.0 +31 12 40           ~ 27 0
4 IRAS 04191+1523 Y*O 04 22 00.439 +15 30 21.21           ~ 183 0
5 NAME Taurus Dark Cloud SFR 04 41.0 +25 52           ~ 3355 0
6 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1333 0
7 NAME Vela XYZ Rad 08 34.0 -45 50           ~ 1094 2
8 NAME Vela-D Molecular Cloud MoC 08 39 -41.0           ~ 43 0
9 Sz 4 TT* 10 57 42.1008128649 -76 59 35.640039635   14.1 14.80   12.17 M4Ve 41 0
10 Ass Cha T 2-21 TT* 11 06 15.3485848381 -77 21 56.737939872   12.58 11.01   9.35 G5Ve 121 0
11 [PCW91] Ced 110 IRS 10 Y*O 11 06 33.38 -77 23 34.6           ~ 57 1
12 NAME Cha I MoC 11 06 48 -77 18.0           ~ 942 1
13 NAME Cha I-S reg 11 07 44 -77 34.8           ~ 9 0
14 NAME Cha in reg 11 09 29.4 -76 33 28           ~ 12 0
15 Ced 112 RNe 11 09 52.4 -76 36 57           ~ 31 0
16 V* WW Cha Or* 11 10 00.0791962314 -76 34 57.971855660   14.74 14.10   10.95 K5 127 0
17 NAME Cha Dark Cloud SFR 11 55 -78.0           ~ 532 1
18 NAME Cha III MoC 12 37.8 -80 15           ~ 122 2
19 NAME Cha II MoC 12 54 -77.2           ~ 295 0
20 NAME Lupus I Cld 15 43 02.1 -34 09 06           ~ 216 0
21 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 675 1
22 NAME Lupus IV MoC 16 03 12.4 -42 07 43           ~ 123 0
23 NAME Lupus III SFR 16 09.6 -39 03           ~ 264 0
24 * rho Oph ** 16 25 35.11766 -23 26 49.8150 4.30 4.85 4.63 4.27 3.96 B2IV+B2V 594 2
25 NAME rho Oph A SM 1N cor 16 26 27.12 -24 23 34.8           ~ 42 0
26 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 2954 0
27 NAME the Pipe Nebula DNe 17 30 -25.0           ~ 323 1
28 DCld 001.6+03.8 DNe 17 35 45 -25 33.2           ~ 47 0
29 NAME Serpens Cloud SFR 18 29 49 +01 14.8           ~ 893 2
30 IC 5146 SFR 21 53 24 +47 16.0   7.82 7.2     ~ 377 2
31 NAME Aql Region reg ~ ~           ~ 289 0

    Equat.    Gal    SGal    Ecl

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2020.01.21-06:35:28

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