2003A&A...410..887G


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.08CET20:33:20

2003A&A...410..887G - Astronomy and Astrophysics, volume 410, 887-896 (2003/11-2)

The distance to the LMC cluster NGC 1866 : clues from the cluster Cepheid population.

GROENEWEGEN M.A.T. and SALARIS M.

Abstract (from CDS):

Recent investigations aimed at estimating the distance to the young LMC cluster NGC 1866 have made use of Red Clump stars in the surrounding LMC field, together with empirical and theoretical Main-Sequence fitting methods, and have found significantly different distances for the field and the cluster, the latter being closer by in distance modulus by Δ(DM)∼0.20mag. In this paper we (re-)consider the Cepheid star population of NGC 1866, to try to shed some light on this discrepancy. By combining various extensive photometric datasets in B, V, I and single-epoch 2mass JHK photometry, PL relationships for the cluster Cepheids are obtained. A comparison between the field LMC and cluster PL relationships for the reddening free Wesenheit index gives a firm determination of the distance between the cluster and the LMC main body (0.04mag in distance modulus, the cluster being more distant) which, coupled to a model for the geometry of the LMC disk, provides Δ(DM) ranging between 0.0 and -0.11mag. The simultaneous comparison of the PL relationships in B, V and I for the cluster and LMC field gives an estimate of the cluster reddening, which results to be E(B-V)=0.12±0.02. This determination is higher than the canonical value of 0.06 mag used in all previous studies, but we show that it is not in contradiction with a re-analysis of independent estimates. The adoption of the LMC extinction law recently presented by Gordon et al. (2003ApJ...594..279G) does not change these results. The cluster Main Sequence fitting distance obtained with this new reddening is DM=18.58±0.08, fully compatible with the Red Clump value of DM=18.53±0.07(random)+0.02–0.05(systematic) and the Cepheid constraint on Δ(DM). Finally, we determined the distance to the cluster by using a Cepheid Wesenheit PL relationship with slope coming from LMC observations, and absolute magnitude zero point calibrated on Hipparcos parallaxes of Galactic Cepheids, in the assumption that the relationship is independent of metallicity; the resulting DM=18.65±0.10 is not an accurate estimate of the LMC distance because of possible metallicity effects but, when compared to the revised Main Sequence fitting value, it points out to a possibly weak dependence of the Wesenheit PL relationship on the Cepheid chemical composition, at least in the period range between 2.5 and 3.5 days.

Abstract Copyright:

Journal keyword(s): stars: distances - Cepheids - Magellanic Clouds - distance scale

CDS comments: Table 1 : stars VN = Cl* NGC 1866 SAB VN.

Simbad objects: 14

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Number of rows : 14

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 SV* HV 12197 Ce* 05 13 13 -65 30.8   16.741 16.102     ~ 28 0
2 SV* HV 12199 Ce* 05 13 19 -65 29.5   16.916 16.289     ~ 30 0
3 SV* HV 12198 cC* 05 13 26.6694544251 -65 27 04.933284395   16.627 15.970   15.230 ~ 40 0
4 SV* HV 12200 Ce* 05 13 36 -65 28.1   16.913 16.247     ~ 15 0
5 Cl* NGC 1866 SAB V4 Ce* 05 13 37.8 -65 26 55   16.715 16.068     ~ 15 1
6 NGC 1866 GlC 05 13 38.920 -65 27 52.75   9.98 9.73     ~ 391 0
7 SV* HV 12202 Ce* 05 13 39 -65 29.0   16.756 16.080     ~ 28 0
8 SV* HV 12203 Ce* 05 13 40 -65 29.6   16.811 16.140     ~ 29 0
9 MACHO 59.5436.172 Ce* 05 13 41.911 -65 27 59.98   16.696 16.54 16.02   ~ 13 0
10 Cl* NGC 1866 WE 1 Ce* 05 13 42.4 -65 27 10   16.622 15.973     ~ 12 0
11 Cl* NGC 1866 ROB B430 Ce* 05 13 42.9 -65 27 00   16.773 16.159     ~ 13 0
12 SV* HV 12204 cC* 05 13 57.8739395146 -65 28 39.329976067   16.18 15.715   15.076 ~ 32 0
13 SV* HV 12205 Ce* 05 14 06 -65 31.4   16.572 12.205     ~ 7 0
14 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15216 1

    Equat.    Gal    SGal    Ecl

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