J/A+A/617/A65 Stellar population of the Arches cluster (Clark+, 2018)
The Arches cluster revisited. I. Data presentation and stellar census.
Clark J.S., Lohr M.E., Najarro F., Dong H., Martins F.
<Astron. Astrophys., 617, A65 (2018)>
=2018A&A...617A..65C 2018A&A...617A..65C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, early-type ; Photometry, HST
Keywords: stars: early-type - stars: evolution - stars: Wolf-Rayet -
open clusters and associations: general - Galaxy: nucleus -
open clusters and associations: individual: Arches cluster
Abstract:
Located within the central region of the Galaxy, the Arches cluster
appears to be one of the youngest, densest, and most massive stellar
aggregates within the Milky Way. As such, it has the potential to be
uniquely instructive laboratory for the study of star formation in
extreme environments and the physics of very massive stars.
To realise this possibility, the fundamental physical properties of
both cluster and constituent stars need to be robustly determined;
tasks we attempt here. Methods. In order to accomplish these goals we
provide and analyse new multi-epoch near-IR spectroscopic data
obtained with the VLT/SINFONI and photometry from the HST/WFC3. We are
able to stack multiple epochs of spectroscopy for individual stars in
order to obtain the deepest view of the cluster members ever obtained.
We present spectral classifications for 88 cluster members, all of
which are WNLh or O stars: a factor of three increase over previous
studies. We find no further examples of Wolf-Rayet stars within the
cluster; importantly no H-free examples were identified. The smooth
and continuous progression in spectral morphologies from O
super/hypergiants through to the WNLh cohort implies a direct
evolutionary connection. We identify candidate giant and main sequence
O stars spectroscopically for the first time. No products of binary
evolution may be unambiguously identified despite the presence of
massive binaries within the Arches.
Notwithstanding difficulties imposed by the highly uncertain
(differential) reddening to the Arches, we infer a main
sequence/luminosity class V turn-off mass of ∼30-38M☉ via the
distribution of spectral types. Analysis of the eclipsing binary F2
suggests current masses of ∼80M☉ and ∼60M☉ for the WNLh
and O hypergiant cohorts, respectively; we conclude that all
classified stars have masses >20M☉. An age of ∼2.0-3.3Myr is
suggested by the turn-off between ∼O4-5 V; constraints imposed by the
supergiant population and the lack of H-free WRs are consistent with
this estimate. While the absence of highly evolved WC stars strongly
argues against the prior occurrence of SNe within the Arches, the
derived age does accommodate such events for exceptionally massive
stars. Further progress will require quantitative analysis of multiple
individual cluster members in addition to further spectroscopic
observations to better constrain the binary and main sequence
populations; nevertheless it is abundantly clear that the Arches
offers an unprecedented insight into the formation, evolution and
death of the most massive stars nature allows to form.
Description:
We present the first results of a multi-epoch spectroscopic survey of
the Arches cluster, co-adding multiple spectra to obtain the deepest
observations ever of the stellar population. We supplement these with
new HST photometric data for confirmed and candidate cluster members.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 99 194 The stellar population of the Arches cluster
--------------------------------------------------------------------------------
See also:
J/ApJ/581/258 : Infrared photometry in the Arches Cluster (Figer+, 2002)
J/MNRAS/371/38 : X-ray observations of the Galaxy center (Wang+, 2006)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID Cluster name (1)
6- 7 I2 h RAh Right ascension (J2000)
9- 10 I2 min RAm Right ascension (J2000)
12- 17 F6.3 s RAs Right ascension (J2000)
19 A1 --- DE- Declination sign (J2000)
20- 21 I2 deg DEd Declination (J2000)
23- 24 I2 arcmin DEm Declination (J2000)
26- 30 F5.2 arcsec DEs Declination (J2000)
32- 36 F5.2 mag F127Mmag ?=- New HST WFC3 F127M magnitude
38- 42 F5.2 mag F139Mmag ?=- New HST WFC3 F139M magnitude
44- 48 F5.2 mag F153Mmag ?=- New HST WFC3 F153M magnitude
50- 54 F5.2 mag F205Wmag ?=- F205W magnitude from Figer et al., 2002,
Cat. J/ApJ/581/258
56- 57 I2 --- NObs ?=- Total number of VLT/SINFONI data-cubes
available for individual objects
59- 60 I2 --- NEpoch ? Number of epochs on which these data were
obtained
61 A1 --- n_NEpoch [abc] Note on NEpoch (2)
63- 80 A18 --- SpType Spectral classification where spectra are
available
82- 99 A18 --- Notes Additional notes (3)
--------------------------------------------------------------------------------
Note (1): nomenclature for cluster members adopted by Figer et al. (2002,
Cat. J/ApJ/581/258, FNNN, [FNG2002] NNN in Simbad) and
Blum et al. (2001AJ....122.1875B 2001AJ....122.1875B, BN, [BSP2001] N in Simbad).
Note (2): Note as follows:
a = 1 epoch of spectroscopy were not employed due to low S/N
b = 2 epochs of spectroscopy were not employed due to low S/N
c = 3 epochs of spectroscopy were not employed due to low S/N
Note (3): additional notes including the presence of radio (data from Lang
et al. 2005AJ....130.2185L 2005AJ....130.2185L, where Radio1 denotes a radio variable source) and
X-ray detections Wang et al. (2006, Cat. J/MNRAS/371/38). As described in
Sect. 3, F11, F46, F51, and F99 appear to be foreground M stars and so are
excluded from this compilation; it would appear likely that other interlopers
may also be present amongst those stars without current spectral
classifications.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 14-Nov-2018