J/AJ/169/174 Nebulae, clusters, & supergiants in M31 with LAMOST (Chen+, 2025)
A comprehensive catalog of emission-line nebulae, star clusters, and supergiants
in M31 from the LAMOST spectroscopic survey.
Chen P., Chen B., Fang X., Yuan H., Zhang B., Zhang X., Sun J., Liu X.
<Astron. J., 169, 174 (2025)>
=2025AJ....169..174C 2025AJ....169..174C
ADC_Keywords: Stars, supergiant; Nebulae; Galaxies, nearby; Clusters, globular;
Clusters, open; Spectroscopy; Radial velocities; Optical
Keywords: Galaxies ; Andromeda galaxy ; Planetary nebulae ; H II regions ;
Star clusters ; Supergiant stars ; Triangulum Galaxy ; Catalogs
Abstract:
Spectroscopic observations of various tracers in nearby galaxies, such
as Andromeda (M31), play a crucial role in identifying and classifying
individual stellar populations and nebular objects, thereby enhancing
our understanding of galactic composition, environment, and dynamics,
as well as stellar evolution. While the Large Sky Area Multi-Object
Fiber Spectroscopic Telescope (LAMOST) survey of M31 has produced
extensive data sets, a comprehensive catalog of emission-line nebulae,
star clusters, and supergiants is yet to be completed. In this paper,
we present a final catalog of 384 emission-line nebulae, 380 star
clusters, and 375 supergiants and candidates in M31, as carefully
selected and identified from the LAMOST spectroscopic database. These
objects were classified using a random forest algorithm, followed by
thorough visual examinations of their spectral characteristics, as
well as morphologies revealed by archive images. For emission-line
nebulae, we measured radial velocities and relative fluxes of emission
lines, enabling further classification of planetary nebulae and H ii
regions. Additionally, we identified 245 emission-line nebulae in M33.
This work lays the data foundation for the study of M31 and offers
valuable tracers to investigate M31's structure and evolution.
Description:
The LAMOST pilot survey was completed in 2012 June, followed by a 5yr
first-phase survey and a subsequent 5yr second-phase survey. In the
first phase only low-resolution (R∼1800) spectroscopy was carried out,
whereas in the second phase both low-resolution and medium-resolution
(R∼7500) observations were made. Our study is based on the LAMOST DR9
v1.0 data release, publicly available in 2022 April. This data release
includes both low- and medium-resolution spectra observed between 2011
October and 2021 June.
For this work, we focus on the low-resolution spectroscopic catalog,
selecting the sky region within 15° centered on M31. This selection
provided us with 648,485 spectra corresponding to 466,680 unique
sources. We also incorporated spectra from earlier LAMOST
low-resolution catalogs. These include low signal-to-noise ratio (S/N)
spectra that the LAMOST 1D pipeline could not classify (A. L. Luo et
al. 2015), leading them to be labeled as "Unknown." In some cases,
nebular spectra with minimal continuum may have been misclassified by
the pipeline, prompting us to search for potential emission-line
nebulae within this subset. This additional step contributed 2950
spectra from 2721 unique objects in the vicinity of M31 and M33.
In total, our initial sample consisted of 651,435 spectra from
469,401 distinct objects. These spectra cover a wavelength range of
∼3700-9100Å, with a resolution of R∼1800 at 5500Å.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
00 42 44.33 +41 16 07.5 M31 = NAME Andromeda Galaxy
01 33 50.89 +30 39 36.6 M33 = NAME Triangulum Galaxy
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 143 629 Emission-line nebulae in M31 and M33 identified
from the LAMOST database
table4.dat 69 380 Star clusters in M31 identified from the LAMOST
database
table5.dat 101 375 Supergiants in M31 identified from the LAMOST
database
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See also:
V/143 : Revised Bologna Catalog of M31 clusters, V.5 (Galleti+ 2012)
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
J/A+A/416/917 : Revised Bologna Cat. of M31 globular clusters (Galleti+, 2004)
J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)
J/MNRAS/369/120 : Kinematic survey of planetary nebulae in M31 (Merrett+, 2006)
J/ApJ/703/441 : Yellow supergiants in M31 (Drout+, 2009)
J/ApJ/703/420 : Red supergiants in M31 (Massey+, 2009)
J/ApJ/750/97 : The yellow and red supergiants of M33 (Drout+, 2012)
J/ApJ/752/95 : PHAT stellar cluster survey. I. Year 1 (Johnson+, 2012)
J/ApJ/758/133 : Metallicity profile of M31 HII regions and PNe (Sanders+, 2012)
J/other/RAA/15.1392 : LAMOST globular clusters in M 31 and M 33 (Chen+, 2015)
J/ApJ/802/127 : PHAT stellar cluster survey. II. AP catalog (Johnson+, 2015)
J/other/RAA/15.1438 : LAMOST new QSOs in M31 and M33 vicinity (Huo+, 2015)
J/AJ/152/45 : LAMOST survey of star clusters in M31. II. (Chen+, 2016)
J/ApJ/825/50 : Variable stars in M31 & M33. III. YSGs & RSGs (Gordon+, 2016)
J/ApJ/826/224 : RSG and foreground candidates in M31 (Massey+, 2016)
J/AJ/152/62 : Revised LGGS UBVRI phot. of M31 and M33 stars (Massey+, 2016)
J/MNRAS/465/4180 : Hα stars in M31 HST photometry (Prichard+, 2017)
J/ApJ/868/55 : Large-scale struct. of M31 halo. II. PAndAS (McConnachie+, 2018)
J/AJ/161/79 : Red supergiant stars in M31 and M33 (Massey+, 2021)
J/ApJ/907/18 : Red Supergiants in M31 & M33. I. Complete sample (Ren+, 2021)
J/A+A/645/A115 : 346 M31 star clusters and their parameters (Wang+, 2021)
J/ApJ/925/76 : M33 with LAMOST surv. sp. I. PNe & HII regions (Alexeeva+, 2022)
J/A+A/658/A51 : New M31 star cluster candidates (Wang+, 2022)
J/ApJ/954/206 : A GCs search in M31 with Gaia, PS1, LAMOST,PAndAS (Wang+, 2023)
J/MNRAS/536/3803 : Line fluxes & abund. in M31 HII regions (Bosomworth+, 2025)
http://www.lamost.org/dr9/v1.0/ : LAMOST DR9 v1.0 website
http://lweb.cfa.harvard.edu/oir/eg/m31clusters/M31_Hectospec.html : Study of
resolved objects in M31 by Nelseon Cadwell+
(accessed on Sep 4 2022)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- LAMOST LAMOST DR9 Source Designation
21- 28 F8.5 deg RAdeg Right ascension (J2000)
30- 37 F8.5 deg DEdeg Declination (J2000)
39- 44 F6.1 --- M06 [32.0/3296.0]? Object ID, Merrett+2006
(J/MNRAS/369/120)
46- 51 F6.1 km/s RVel-M06 [-660/220]? Radial velocity, Merrett+2006
(J/MNRAS/369/120)
53- 55 I3 --- B24 [3/294]? Object ID, Bosomworth+2025
(J/MNRAS/536/3803)
57- 62 F6.1 km/s RVel [-693/226] Total radial velocity (1)
64- 67 F4.1 km/s e_RVel [0.2/32.6] Uncertainty in RVel
69- 74 F6.1 km/s RVel-b [-691/222.1]? Radial velocity from
blue-spectrum nebular lines (1)
76- 79 F4.1 km/s e_RVel-b [0.2/35.7]? Uncertainty in RVel-b
81- 86 F6.1 km/s RVel-r [-708.2/232]? Radial velocity from
red-spectrum nebular lines (1)
88- 91 F4.1 km/s e_RVel-r [0.3/40.1]? Uncertainty in RVel-r
93- 97 F5.2 --- N2 [-2/1]? Line ratio, [NII]/Hα
99- 103 F5.2 --- O3 [-2/2]? Line ratio, [OIII] 5007A/Hβ
105- 107 A3 --- Host Host, M31 or M33
109- 113 A5 --- Lit Literature classification (2)
115- 121 A7 --- Class New classification made in this work based on
the LAMOST database (3)
123- 143 A21 --- Comments Comments, including possible other sources
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Note (1): Blue- and red- velocities refer to the radial velocities
derived exclusively from nebular emission lines in the blue and
red spectral ranges, respectively. The total velocity is
determined by combining all available nebular emission lines
across both ranges. These velocities (RVel, RVel-b, RVel-r)
represent line components and are not direct measurements
provided by the LAMOST pipeline, but rather values determined
through our analysis. Specifically, they are derived as mean
values weighted by the velocities determined from individual lines.
Note (2): Literature classification as follows :
EmObj = Emission-line object (35 occurrences)
HII = HII region (165 occurrences)
PN = Planetary nebula (136 occurrences)
PN_c = Planetary nebula candidate (98 occurrences)
SNR = Supernova remnant (3 occurrences)
Note (3): New classification made in this work based on the LAMOST database
as follows:
HII = HII region (157 occurrences)
HII_c = HII region candidate (164 occurrences)
PN = Planetary nebula (132 occurrences)
PN_c = Planetary nebula candidate (137 occurrences)
Unknown = Unclassified nebula (39 occurrences)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star cluster name (1)
12- 19 F8.5 deg RAdeg Right ascension (J2000)
21- 28 F8.5 deg DEdeg Declination (J2000)
30- 35 F6.1 km/s RVel-RBC [-706/70]? Radial velocity, Revised Bologna
Catalog (V/143)
37- 43 F7.2 km/s RVel-Cad [-701/40]? Radial velocity, Nelson Cadwell (2)
45- 50 F6.1 km/s RVel [-735/31.3] Radial velocity, LAMOST
52- 59 F8.1 km/s e_RVel [1.2/268162] Uncertainty in RVel
61- 67 F7.1 --- APID [1.0/15121.0]? Andromeda project
identification number from Johnson+2015
(J/ApJ/802/127)
69 I1 --- Status [1/2] Classification status (3)
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Note (1): Star cluster names were adopted from previous work, including the
Revised Bologna Catalog version 5 (V/143), Huxor+ (2014MNRAS.442.2165H 2014MNRAS.442.2165H),
and Chen+2015 (J/other/RAA/15.1392).
Note (2): Nelson Cadwell's study of resolved objects in M31
(http://lweb.cfa.harvard.edu/oir/eg/m31clusters/M31_Hectospec.html,
accessed on Sep 4 2022)
Note (3): Classification status as follows:
1 = confirmed star cluster (344 occurrences)
2 = candidate star cluster (36 occurrences)
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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 --- LAMOST LAMOST DR9 Source Designation
21- 28 F8.5 deg RAdeg Right ascension (J2000)
30- 37 F8.5 deg DEdeg Declination (J2000)
39- 44 F6.1 km/s RVel [-605/47]? LAMOST radial velocity
46- 53 F8.1 km/s e_RVel [1/298041]? Uncertainty in RVel
55- 60 F6.1 km/s RVel-exp [-537/-53] Expected radial velocity (1)
62- 65 F4.1 kpc Rgal [1.1/25] Deprojected galactocentric distance
67- 72 F6.4 --- PM31 [0/1.0] Probability, M31 member
74- 79 F6.4 --- PMW [0/1] Probability, Milky Way member
81- 86 F6.3 mag Vmag [15.3/23.3]? Local Group Galaxies Survey
(J/AJ/131/2478) V-band Vega magnitude
88- 93 F6.3 mag B-V [-4.2/2.45]? Local Group Galaxies Survey
(J/AJ/131/2478) B-V color
95- 99 A5 --- Type Classification type (2)
101 I1 --- W24 [1/1]? W24=1, common entries identified in
Wu+2025 [2025RAA....25a5012W 2025RAA....25a5012W]
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Note (1): From Equation 4.: RVel-exp = -311.8 + 242.0(X/Rgal)
Note (2): Known supergiants are labeled with types as reported in literature
and candidates are denoted with "_c". Classification type as follows:
WR = Wolf-Rayet (4 occurrences)
bsg = Blue supergiant (17 occurrences)
bsg_c = Blue supergiant, candidate (19 occurrences)
rsg = Red supergiant (40 occurrences)
rsg_c = Red supergiant, candidate (10 occurrences)
sg_c = Supergiant candidate identified in this study (192 occurrences)
star = Objects in the "Stars in the M31 Catalog" by Nelson Cadwell
(40 occurrences)
ysg = Yellow supergiant (17 occurrences)
ysg_c = Yellow supergiant, candidate (36 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 06-Jan-2026