J/ApJ/759/11 Wolf-Rayet content of M31 (Neugent+, 2012)
The Wolf-Rayet content of M31.
Neugent K.F., Massey P., Georgy C.
<Astrophys. J., 759, 11 (2012)>
=2012ApJ...759...11N 2012ApJ...759...11N
ADC_Keywords: Equivalent widths ; Spectral types ; Stars, Wolf-Rayet ;
Spectroscopy ; Galaxies, nearby
Keywords: galaxies: individual: M31; galaxies: stellar content; Local Group;
stars: evolution; stars: Wolf-Rayet; supergiants
Abstract:
Wolf-Rayet (WR) stars are evolved massive stars, and the relative
number of WC-type and WN-type WRs should vary with the metallicity of
the host galaxy, providing a sensitive test of stellar evolutionary
theory. However, past studies of the WR content of M31 have been
biased toward detecting WC stars, as their emission-line signatures
are much stronger than those of WNs. Here, we present the results of a
survey covering all of M31's optical disk (2.2deg2), with sufficient
sensitivity to detect the weaker-lined WN types. We identify 107 newly
found WR stars, mostly of WN type. This brings the total number of
spectroscopically confirmed WRs in M31 to 154, a number we argue is
complete to ∼95%, except in regions of unusually high reddening. This
number is consistent with what we expect from the integrated Hα
luminosity compared to that of M33. The majority of these WRs formed
in OB associations around the Population I ring, although 5% are truly
isolated. Both the relative number of WC- to WN-type stars as well as
the WC subtype distribution suggest that most WRs exist in
environments with higher-than-solar metallicities, which is consistent
with studies of M31's metallicity. Although the WC to WN ratio we find
for M31 is much lower than that found by previous studies, it is still
higher than what the Geneva evolutionary models predict. This may
suggest that Roche-lobe overflow produces the excess of WC stars
observed at high metallicity, or that the assumed rotational
velocities in the models are too high.
Description:
To identify potential M31 WR candidates, we used a method almost
identical to that used by Neugent & Massey (2011, Cat. J/ApJ/733/123)
when surveying M33, with the notable exception that we did not use
photometric criteria in this study.
We obtained images of M31 - through three filters: one is centered on
WCs' strongest line, CIII4650, another on WNs' strongest line,
HeII4686, while the third is centered on the continuum, λ4750 -
using the Kitt Peak 4m Mayall telescope and the Mosaic CCD camera on
(UT) 2001 November 3-6. The entire optical disk of M31 was imaged
using 10 overlapping 36'x36' fields covering a 2.2deg2 area.
To confirm new M31 WR candidates and reclassify previously known WRs,
we used the multi-object fiber-fed spectrograph Hectospec on the 6.5m
MMT. The data were all taken with the 270 line/mm grating, resulting
in spectral coverage from 3700 to 9000Å, at a resolution of 6Å
(5 pixels).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 104 154 M31 WR stars with new spectroscopic data
table5.dat 124 154 Spectroscopically confirmed M31 Wolf-Rayet stars
spec/* . 285 *Individual fits spectra for 250 newly observed
WR stars of M31 and M33
(34 stars with a second spectrum "alt" + readme)
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Note on spec/* : The spectra are unnormalized. This data set includes spectra
of 150 of the 154 WRs known in M31 plus 84 of the 206 WRs known in M33,
as well as 12 M33 stars we consider to be of Of-type.
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See also:
III/215 : 7th Catalog of Galactic Wolf-Rayet stars (van der Hucht, 2001)
III/143 : Spectrophotometry of Wolf-Rayet Stars (Torres-Dodgen+ 1988)
J/AJ/143/149 : NIR spectro. of Galactic Wolf-Rayet stars. II. (Shara+, 2012)
J/ApJ/733/123 : The Wolf-Rayet content of M33 (NGC 598) (Neugent+, 2011)
J/A+A/534/A55 : Deep XMM-Newton Survey of M31 (Stiele+, 2011)
J/A+A/509/A61 : Long slit spectroscopy in M31 (Saglia+, 2010)
J/ApJ/703/420 : Red supergiants in M31 (Massey+, 2009)
J/AJ/134/2474 : Hα em.-line stars in 7 dwarfs galaxies (Massey+, 2007)
J/AJ/133/2393 : UBVRI phot. in 7 Local Group dwarfs galaxies (Massey+, 2007)
J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)
J/A+A/373/63 : M31 second ROSAT PSPC survey (Supper+, 2001)
J/ApJ/505/793 : New WR star in M33 (Massey+, 1998)
J/AJ/110/2715 : UBV photometry in NGC 6822, M31 and M33 (Massey+ 1995)
J/A+AS/102/251 : Objective-prism survey of M31 em. objects (Meyssonnier+ 1993)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Star designation (JHHMMSS.ss+DDMMSS.s
for LGGS or XHHMMSS.ss+DDMMSS.s for new) (5)
21- 32 A12 --- NSpT New spectral type designation
34 A1 --- f_NSpT [d] 2 new spectra were obtained and compared
36- 45 A10 --- OID Previous data identifier (G1)
47 A1 --- ni [e] star not found in our imaging survey
49- 57 A9 --- PSpT Previous spectral type
59- 63 A5 --- r_PSpT Reference for PSpT (4)
65- 68 I4 0.1nm EW3 [2/1160]? Equivalent width of
CIII(4650)/HeII(4686) feature
70- 71 I2 0.1nm FW3 [3/87]? FWHM of CIII(4650)/HeII(4686) feature
73- 76 I4 0.1nm EW4 [8/1160]? Equivalent width of CIV(5806) line
78- 79 I2 0.1nm FW4 [15/87]? FWHM of CIV(5806) line
81-104 A24 --- Comment Additional comments
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Note (4): Reference as follows:
1 = Moffat & Shara 1983ApJ...273..544M 1983ApJ...273..544M
2 = Armandroff & Massey 1991AJ....102..927A 1991AJ....102..927A
3 = Schild et al. 1990A&A...237..169S 1990A&A...237..169S
4 = Willis et al. 1992A&A...261..419W 1992A&A...261..419W
5 = Massey et al. 1995, Cat. J/AJ/110/2715
6 = Massey et al. 1987AJ.....94.1538M 1987AJ.....94.1538M
7 = Massey et al. 1986AJ.....92.1303M 1986AJ.....92.1303M
8 = Massey 1998salg.conf...95M
9 = Moffat & Shara 1987ApJ...320..266M 1987ApJ...320..266M
Note (5): J004406.39+411921.0, J004425.43+412044.7, J004513.68+413742.5 and
J004628.51+421127.6 added by CDS in Table 2 for technical reasons.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Star designation (as in table 2)
21- 24 F4.2 --- rho [0/1] Normalized galactocentric distance ρ
within M31 plane (ρ=1 is R=95.3")
26- 35 A10 --- SpT Spectral type adopted
37 A1 --- f_SpT [f] Spectral type from literature (1)
39- 43 F5.2 mag Vmag [17.5/22.8]? LGGS Apparent V band magnitude
45- 49 F5.2 mag B-V [-0.5/0.8]? LGGS (B-V) color index
51- 54 F4.1 mag VMag [-7.5/-3]? Absolute V band magnitude (2)
56- 60 A5 --- Assoc OB association (3)
62- 71 A10 --- OID Previous identifier (G1)
73- 96 A24 --- FileName1 Name of FITS file in subdirectory spec
98-124 A27 --- FileName2 Name of second FITS file (alternative
spectrum) in subdirectory spec
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Note (1):
f = Spectral type from Massey and Johnson, 1998, Cat. J/ApJ/505/793,
and references therein.
Note (2): The absolute visual magnitude computed assuming E(B-V)=0.2
(AV=0.62) for stars with B-V≤0.2. We assumed a true distance
modulus of 24.4 (0.76Mpc) using van den Bergh 2000glg..book.....V 2000glg..book.....V
Note (3): OB associations as identified by van den Bergh
(1964ApJS....9...65V 1964ApJS....9...65V; (<[V64] NNN> in Simbad).
* Parenthesis means that the star is close to, but not in, the association.
* "I" means that the star is located in the Population I ring,
but not in an identified OB association.
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Global notes:
Note (G1): Previous identifications:
OB = designations from Massey et al. 1986AJ.....92.1303M 1986AJ.....92.1303M
( in Simbad)
except for OB 32, from Armandroff & Massey 1991AJ....102..927A 1991AJ....102..927A
(<[C92] OB32-WR1> in Simbad)
MS = Moffat & Shara 1983ApJ...273..544M 1983ApJ...273..544M (<[MS83] NN> in Simbad) with revised
coordinates by Massey and Johnson, 1998, Cat. J/ApJ/505/793
(<[MJ98] WR NNNA> in Simbad);
IT = Moffat & Shara 1987ApJ...320..266M 1987ApJ...320..266M (<[MS87] ITN-NN> in Simbad) with
revised coordinates by Massey and Johnson, 1998, Cat. J/ApJ/505/793
(<[MJ98] WR NNNA> in Simbad);
New = the star is newly identified WR star as part of the present program.
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History:
From electronic version of the journal
02-Sep-2014: Insert into VizieR
19-Apr-2023: Online coordinates corrected (4 objects added in Table 2).
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 09-Jul-2014