2012A&A...547A..85B


Query : 2012A&A...547A..85B

2012A&A...547A..85B - Astronomy and Astrophysics, volume 547A, 85-85 (2012/11-1)

Molecular gas and stars in the translucent cloud MBM 18 (LDN 1569).

BRAND J., WOUTERLOOT J.G.A. and MAGNANI L.

Abstract (from CDS):

We investigate star formation in translucent, high-latitude clouds. Our aim is to understand the star-formation history and rate in the solar neighbourhood. We used spectroscopic observations of newly found candidate Hα emission-line stars to establish their pre-main-sequence nature. The environment was studied through molecular line observations of the cloud (MBM 18/LDN 1569) in which the stars are presumably embedded. Ten candidate Hα emission-line stars were found in an objective grism survey of a ∼1 square degree region in MBM 18, of which seven have been observed spectroscopically in this study. Four of these have weak (|W(Hα)|≲5Å) Hα emission, and six out of seven have spectral types M1-M4 V. One star is of type F7-G1 V, and has Hα in absorption. The spectra of three of the M-stars may show an absorption line of LiI, although none of these is an unambiguous detection. The M-stars lie at distances between ∼60pc and 250pc, while most distance determinations of MBM 18 found in the literature agree on 120-150pc. For the six M-stars a good fit is obtained with pre-main-sequence isochrones indicating ages between 7.5 and 15Myr. The mass of the molecular material, derived from the integrated 12CO(1-0) emission, is ∼160M (for a distance of 120 pc). This is much smaller than the virial mass (∼103M), and the cloud is not gravitationally bound. Using a clump-finding routine, we identify 12 clumps from the CO-data, with masses between 2.2 and 22M. All clumps have a virial mass at least six times higher than their CO-mass, and thus none are in gravitational equilibrium. A similar situation is found from higher-resolution CO-observations of the northern part of the cloud. Considering the relative weakness or absence of the Hα emission, the absence of other emission lines, and the lack of clear LiI absorption, the targets are not T Tauri stars. With ages between 7.5 and 15Myr they are old enough to explain the lack of lithium in their spectra. Based on the derived distances, some of the stars may lie inside the molecular cloud. From the fact that the cloud as a whole, as well as the individual clumps, are not gravitationally bound, in combination with the ages of the stars we conclude that it is not likely that (these) stars were formed in MBM 18.

Abstract Copyright:

Journal keyword(s): stars: formation - stars: emission-line, Be - ISM: clouds - ISM: individual objects: MBM 18 (LDN 1569)

VizieR on-line data: <Available at CDS (J/A+A/547/A85): table1.dat fig_a1a.dat fig_a1b.dat fig_a1c.dat fig_a1d.dat fig_a1e.dat fig_a1f.dat fig_a2.dat>

Nomenclature: Table 1: [BWM2012] HaNN (Nos Ha1-Ha10).

CDS comments: 1WGA J043.0+0027 not found (misprint).

Simbad objects: 23

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Number of rows : 23
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME W 3 OH HII 02 27 04.1 +61 52 22           ~ 971 2
2 V* FS Cet ** 02 35 07.5939678751 +03 43 56.817951540 11.027 12.209 12.412 12.325 11.968 DA1+dM 358 0
3 LDN 1457 DNe 02 55.9 +19 35           ~ 81 1
4 LDN 1453 DNe 02 56.0 +20 17           ~ 22 0
5 LDN 1454 DNe 02 56.8 +20 12           ~ 23 0
6 MBM 12 MoC 02 56 50 +19 32.0           ~ 212 1
7 LDN 1458 DNe 02 57.8 +20 12           ~ 21 1
8 MBM 16 MoC 03 19 04.1 +11 34 52           ~ 57 0
9 RX J0401.4+0106 X 04 01 24.0 +01 06 00           ~ 1 0
10 LDN 1569 MoC 04 02.4 +01 18           ~ 46 0
11 RX J0403.0+0027a X 04 03 00.0 +00 27 00           ~ 1 0
12 LDN 1642 MoC 04 35 18 -14 13.9           ~ 141 0
13 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 3791 0
14 RAFGL 618 pA* 04 42 53.6245215366 +36 06 53.397219192   16.32   12.59   C-rich 971 0
15 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2105 1
16 LDN 1641 MoC 05 39.0 -07 00           ~ 446 0
17 Feige 34 HS* 10 39 36.7377085527 +43 06 09.209752646 9.613 10.91 11.14 11.319 11.464 sdOp 626 0
18 NAME TW Hya Association As* 11 01.9 -34 42           ~ 864 0
19 MBM 40 MoC 16 10 34 +21 49.3           ~ 67 0
20 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 2041 1
21 W 49n HII 19 10 13.2 +09 06 12           ~ 427 3
22 W 51 SNR 19 23 50 +14 06.0           ~ 1193 1
23 GRS G081.70 +00.50 SFR 20 39 01.6 +42 19 38           O4.5 986 0

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2021.10.28-23:00:15

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