J/ApJ/947/54 High-mass SFR masers with VLBI & external MW-like gal. (Xu+, 2023)
What does the Milky Way look like?
Xu Y., Hao C.J., Liu D.J., Lin Z.H., Bian S.B., Hou L.G., Li J.J.,
Li Y.J.
<Astrophys. J., 947, 54 (2023)>
=2023ApJ...947...54X 2023ApJ...947...54X
ADC_Keywords: Star Forming Region; Interferometry; Masers; Space velocities;
Parallaxes, trigonometric; Proper motions; Milky Way;
Morphology; Galaxies, optical
Keywords: Galaxy structure ; Milky Way Galaxy ; Trigonometric parallax
Abstract:
In spite of much work, the overall spiral structure morphology of the
Milky Way remains somewhat uncertain. In the last two decades,
accurate distance measurements have provided us with an opportunity to
solve this issue. Using the precise locations of very young objects,
for the first time, we propose that our galaxy has a multiple-arm
morphology that consists of two-arm symmetry (the Perseus and Norma
Arms) in the inner parts and that extends to the outer parts, where
there are several long, irregular arms (the Centaurus, Sagittarius,
Carina, Outer, and Local Arms).
Description:
VLBI at radio wavelengths has been used to detect a large amount of
masers associated with high-mass star-forming regions (HMSFRs), and
they can be used to map the spiral structure of the MW from the solar
neighborhood to the Galactic center (GC) and beyond. Table 1 lists the
coordinates and parallaxes of 204 HMSFR masers measured with VLBI
techniques, including the National Radio Astronomy Observatory's Very
Long Baseline Array, the Japanese VLBI Exploration of Radio Astrometry
project, the European VLBI Network, and the Australian Long Baseline
Array. For the masers listed in Table 1, 199 were summarized by R19
(Reid+ 2019, J/ApJ/885/131), and five have been newly reported by
Xu+ 2021ApJS..253....1X 2021ApJS..253....1X and Bian+ 2022AJ....163...54B 2022AJ....163...54B in the past 2yr.
See Section 2.
We obtain a sample of 185 external MW-like galaxies from the the Sloan
Digital Sky Survey (SDSS) DR7 in the g band or Digitized Sky Survey
(DSS) in the blue band. See Appendix B.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 129 204 The astrometric parameters of high-mass
star-forming region (HMSFR) masers
tableb1.dat 56 187 The properties of the external MW-like galaxies;
see Appendix B
refs.dat 72 75 References
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See also:
VIII/39 : Composite CO Survey of the Milky Way (Dame+ 1987)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/A+A/397/133 : Star-forming complexes in the Galaxy (Russeil+, 2003)
J/A+A/569/A125 : Spiral structure of the Milky Way (Hou+, 2014)
J/ApJ/798/L27 : CO obs. of MoCs in the 2nd quadrant (Sun+, 2015)
J/ApJS/224/7 : CO obs. of the outer arm in the 2nd quadrant (Du+, 2016)
J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)
J/A+A/616/A10 : Open clusters GaiaDR2 HR diag. (Gaia Collaboration, 2018)
J/A+A/616/L15 : Parallaxes and Proper Motions of OB stars (Xu+, 2018)
J/other/RAA/18.146 : Spiral structure of the Milky Way (Xu+, 2018)
J/ApJ/885/131 : High-mass SFR plx & proper motion with VLBI (Reid+, 2019)
J/A+A/652/A102 : 3794 open clusters parameters (Hao+, 2021)
J/A+A/651/A104 : Spiral arms Gaia EDR3 (Poggio+, 2021)
J/A+A/645/L8 : Plxs & proper motions of OB stars from Gaia (Xu+, 2021)
J/A+A/661/A118 : Open clusters found with OCfinder (Castro-Ginard+, 2022)
J/A+A/660/A4 : Gaia EDR3 new Galactic open clusters (Hao+, 2022)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Source name
16- 30 A15 --- Alias Alias name
32- 33 I2 h RAh Hour of Right Ascension (J2000)
35- 36 I2 min RAm Minute of Right Ascension (J2000)
38- 44 F7.4 s RAs Second of Right Ascension (J2000)
47 A1 --- DE- Sign of the Declination (J2000)
48- 49 I2 deg DEd Degree of Declination (J2000)
51- 52 I2 arcmin DEm Arcminute of Declination (J2000)
54- 59 F6.3 arcsec DEs Arcsecond of Declination (J2000)
63- 67 F5.3 mas plx [0.049/2.5] Trigonometric Parallax (1)
69- 73 F5.3 mas e_plx [0.005/0.2] Uncertainty in plx
77- 82 F6.2 mas/yr pmE [-6.9/3.2] Eastward Proper Motion; motion in RA
multiplied by cos(Dec) (2)
84- 87 F4.2 mas/yr e_pmE [0.06/3.1] Uncertainty in pmE
91- 96 F6.2 mas/yr pmN [-9.4/2.7] Northward Proper Motion (2)
98-101 F4.2 mas/yr e_pmN [0.1/3.71] Uncertainty in pmN
105-108 I4 km/s VLSR [-76/121] Local Standard of Rest velocity (2)
110-111 I2 km/s e_VLSR [3/40] Uncertainty in VLSR
114-116 A3 --- Arm Spiral arm designator (3)
119-129 A11 --- Ref Reference(s) designators (see refs.dat file)
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Note (1): The typical parallax accuracy of the masers is ∼20uas, and 19 of
them have accuracies of 10uas or better.
Note (2): Motion components and their uncertainties are meant to reflect that
of the central star that excites the masers, and may be larger than
formal measurement uncertainties quoted in some papers.
Note (3): Arm as follows:
Nor = Norma arm;
Out = Outer arm;
Sgr = Sagittarius arm;
Car = Carina arm;
Loc = Local arm;
Per = Perseus arm;
LoS = Local arm spur;
AqS = Aquarius spur;
??? = Unassigned.
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Name of the external galaxy
15- 25 A11 --- MType Morphological type from SIMBAD database (1)
27- 30 F4.2 arcmin Dmaj [0.5/6.2] Major diameter of galaxy from SIMBAD
database
32- 35 F4.2 arcmin Dmin [0.5/3.6] Minor diameter of galaxy from SIMBAD
database
37- 44 A8 --- Survey Image data come from DSS blue band or SDSS DR7
g band
46 A1 --- EEtype Spiral arm classes (2)
48- 51 A4 --- Inner Has inner two arms or not (3)
53 A1 --- Start Inner spiral arms start from end of bar or not
55- 56 A2 --- EE87 Arm classes in
Elmegreen & Elmegreen (1987ApJ...314....3E 1987ApJ...314....3E) (4)
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Note (1): The colons are used to indicate that the family and variety are
uncertain interpretations in this case.
Note (2): Class as follows:
F = flocculent (75 occurrences)
M = multiple-arm (99 occurrences)
G = grand-design (12 occurrences)
? = unclassified (1 occurrence)
Note (3): If not, the number of inner arms will present in the (),
and "?" represent the number of inner arms is hard to identify.
Note (4): 1-4 represents flocculent galaxies, 5-9 represents
multiple-arm galaxies, and 12 for a grand-design galaxy.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference code
4- 32 A29 --- Auth First author's name(s)
34- 52 A19 --- BibCode Bibcode of the reference
54- 72 A19 --- Cat VizieR catalog reference
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Apr-2025