Query : 2009A&A...501..563E

2009A&A...501..563E - Astronomy and Astrophysics, volume 501, 563-583 (2009/7-2)

The massive star initial mass function of the Arches cluster.


Abstract (from CDS):

The massive Arches cluster near the Galactic center should be an ideal laboratory for investigating massive star formation under extreme conditions. But it comes at a high price: the cluster is hidden behind several tens of magnitudes of visual extinction. Severe crowding requires space or AO-assisted instruments to resolve the stellar populations, and even with the best instruments interpreting the data is far from direct. Several investigations using NICMOS and the most advanced AO imagers on the ground revealed an overall top-heavy IMF for the cluster, with a very flat IMF near the center. There are several effects, however, that could potentially bias these results, in particular the strong differential extinction and the problem of transforming the observations into a standard photometric system in the presence of strong reddening. We present new observations obtained with the NAOS-Conica (NACO) AO-imager on the VLT. The problem of photometric transformation is avoided by working in the natural photometric system of NACO, and we use a Bayesian approach to determine masses and reddenings from the broad-band IR colors. A global value of Γ=-1.1±0.2 for the high-mass end (M>10M) of the IMF is obtained, and we conclude that a power law of Salpeter slope cannot be discarded for the Arches cluster. The flattening of the IMF towards the center is confirmed, but is less severe than previously thought. We find Γ=-0.88±0.20, which is incompatible with previous determinations. Within 0.4pc we derive a total mass of ∼2.0(±0.6)x104M for the cluster and a central mass density ρ= 2(±0.4)x105M/pc3 that confirms Arches as the densest known young massive cluster in the Milky Way.

Abstract Copyright:

Journal keyword(s): Galaxy: open clusters and associations: individual: Arches - stars: early-type - instrumentation: adaptive optics - ISM: dust, extinction - stars: luminosity function, mass function

VizieR on-line data: <Available at CDS (J/A+A/501/563): table2.dat table3.dat table5.dat>

Nomenclature: Table 2: [ESM2009] NNN (Nos 1-427).

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6570 1
2 TYC 7052-1131-1 * 04 49 54.2419452720 -35 11 13.828816680   12.74 12.54     ~ 6 0
3 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 16539 1
4 RMC 136 Cl* 05 38 42.396 -69 06 03.36           ~ 1910 1
5 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13458 0
6 NAME Arches Cluster Cl* 17 45 50.5 -28 49 28           ~ 701 0
7 NAME Quintuplet Cluster OpC 17 46 13.9 -28 49 48           ~ 503 0

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