J/ApJ/961/4 Protostellar cores in Sgr B2 N and M from ALMA (Budaiev+, 2024)
Protostellar cores in Sagittarius B2 N and M.
Budaiev N., Ginsburg A., Jeff D., Goddi C., Meng F., Sanchez-Monge A.,
Schilke P., Schmiedeke A., Yoo T.
<Astrophys. J., 961, 4 (2024)>
=2024ApJ...961....4B 2024ApJ...961....4B
ADC_Keywords: Photometry, millimetric/submm; YSOs; Stars, masses;
Star Forming Region; Cross identifications
Keywords: Star formation ; Initial mass function ; Star forming regions ;
Protostars ; Young stellar objects
Abstract:
We present 500 and 700au resolution 1 and 3mm Atacama Large
Millimeter/submillimeter Array observations, respectively, of
protostellar cores in protoclusters Sagittarius B2 (Sgr B2) North (N)
and Main (M), parts of the most actively star-forming cloud in our
Galaxy. Previous lower-resolution (5000au) 3mm observations of this
region detected ∼150 sources inferred to be young stellar objects
(YSOs) with M>8M☉. With a 10-fold increase in resolution, we
detect 371 sources at 3mm and 218 sources in the smaller field of view
at 1mm. The sources seen at low resolution are observed to fragment
into an average of two objects. About one-third of the observed
sources fragment. Most of the sources we report are marginally
resolved and are at least partially optically thick. We determine that
the observed sources are most consistent with Stage 0/I YSOs, i.e.,
rotationally supported disks with an active protostar and an envelope,
that are warmer than those observed in the solar neighborhood. We
report source-counting-based inferred stellar mass and the star
formation rate of the cloud: 2800M☉ and 0.0038M☉/yr for
Sgr B2 N and 6900M☉ and 0.0093M☉/yr for Sgr B2 M,
respectively.
Description:
We report follow-up Atacama Large Millimeter/submillimeter Array
(ALMA) observations to ALMA project 2013.1.00269.S, which covered a
15x15pc area around the Sagittarius B2 (Sgr B2) complex at 3mm with
∼5000au resolution. Our data cover Sgr B2 North (N) and Main (M) at
3mm and at 1mm.
This paper utilizes the data from ALMA Cycle 4 project 2016.1.00550.S.
The observations consist of two pointings centered on Sgr B2 N
(RAICRS=17:47:19.925;DE_ICRS=-28:22:18.608) and Sgr B2 M
(RAICRS=17:47:20.174;DEICRS=-28:23:04.788) with the 12m antennas.
Both locations were observed in Band 3 and Band 6 with resolution of
0.096"x0.073" (∼700au) and 0.083"x0.038" (∼500au), respectively.
The central spectral window frequencies are 217.84, 219.79, 231.80,
and 233.67GHz for Band 6 and 85.47, 87.37, 97.42, and 99.42GHz for
Band 3.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
17 47 19.92 -28 22 18.6 NAME Sgr B2 (N) = DGSW 68
17 47 20.17 -28 23 04.7 NAME Sgr B2 (M) = DGSW 66
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4a.dat 114 197 Sgr B2 M ALMA 3mm (Band 3) continuum catalog
table4b.dat 99 108 Sgr B2 M ALMA 1mm (Band 6) continuum catalog
table4c.dat 107 215 Sgr B2 N ALMA 3mm (Band 3) continuum catalog
table4d.dat 95 135 Sgr B2 N ALMA 1mm (Band 6) continuum catalog
--------------------------------------------------------------------------------
See also:
J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)
J/AJ/139/1695 : Celestial Reference Frame at 24 and 43 GHz (Lanyi+, 2010)
J/A+A/586/A50 : Central Molecular Zone H2CO temperature maps (Ginsburg+, 2016)
J/A+A/604/A6 : SgrB2 ALMA continuum and spectral index (Sanchez-Monge+, 2017)
J/ApJ/869/L41 : DSHARP I. Sample, ALMA obs. log and overview (Andrews+, 2018)
J/ApJ/853/171 : mm point sources in the extended Sgr B2 cloud (Ginsburg+, 2018)
J/ApJ/890/130 : VANDAM survey of Orion protostars. II. (Tobin+, 2020)
J/ApJ/923/221 : ALMA obs. of protoplanetary disks in ONC & OMC1 (Otter+, 2021)
J/A+A/666/A31 : Sgr B2 UCHII regions in 6, 22.4 and 96GHz (Meng+, 2022)
Byte-by-byte Description of file: table4a.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/361] Source ID
5- 10 F6.2 mJy SnuF [0.07/728] Dendrogram contour flux
12- 17 F6.2 mJy/beam SnuPk [0.25/187] Brightest pixel flux
19- 23 F5.3 mJy/beam ErrSnu [0.05/0.2] Noise
25- 29 F5.3 arcsec FWHMmaj [0.036/0.31] Source FWHM (maj)
31- 35 F5.3 arcsec FWHMmin [0.02/0.23] Source FWHM (min)
37- 38 I2 h RAh [17] Hour of Right Ascension (J2000)
40- 41 I2 min RAm [47] Minute of Right Ascension (J2000)
43- 49 F7.4 s RAs [17.4/21.6] Second of Right Ascension (J2000)
51 A1 --- DE- [-] Sign of Declination (J2000)
52- 53 I2 deg DEd [28] Degree of Declination (J2000)
55- 56 I2 arcmin DEm [22/23] Arcminute of Declination (J2000)
58- 63 F6.3 arcsec DEs Arcsecond of Declination (J2000)
65 I1 --- Score [0/2] 2 = core, 1 = likely core (G1)
67- 74 A8 --- OType Source type (1)
76- 78 I3 --- IDG18 [71/271]? Source ID match from G18
(Ginsburg+ 2018, J/ApJ/853/171) catalog
80- 86 A7 --- OIDG18 Source OID match from G18
(Ginsburg+ 2018, J/ApJ/853/171) catalog
88- 90 I3 --- IDB6 [4/301]? Source ID match from Band 6
92- 95 I4 K TB [4/3766] Brightness temperature
97- 102 F6.3 --- alpha [-1.1/3.5]? Spectral index
104- 108 F5.3 --- e_alpha [0.002/0.4]? Uncertainty on spectral index
110- 114 F5.1 Msun Mass [2.2/240.7]? Core mass
--------------------------------------------------------------------------------
Note (1): Type as follows:
core = core (168 occurrences)
HII = known hypercompact and ultracompact HII region (14 occurrences)
HII_cand = HII region candidate (12 occurrences)
HII_new = new hypercompact HII region (3 occurrences)
See Section 3.1
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4b.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [4/301] Source ID
5- 9 F5.1 mJy SnuF [0.5/635] Dendrogram contour flux
11- 15 F5.1 mJy/beam SnuPk [1.3/146] Brightest pixel flux
17- 21 F5.3 mJy/beam ErrSnu [0.2/1.1] Noise
23- 27 F5.3 arcsec FWHMmaj [0.028/0.35] Source FWHM (maj)
29- 33 F5.3 arcsec FWHMmin [0.014/0.16] Source FWHM (min)
35- 36 I2 h RAh [17] Hour of Right Ascension (J2000)
38- 39 I2 min RAm [47] Minute of Right Ascension (J2000)
41- 47 F7.4 s RAs [18.7/20.5] Second of Right Ascension (J2000)
49 A1 --- DE- [-] Sign of Declination (J2000)
50- 51 I2 deg DEd [28] Degree of Declination (J2000)
53- 54 I2 arcmin DEm [22/23] Arcminute of Declination (J2000)
56- 61 F6.3 arcsec DEs Arcsecond of Declination (J2000)
63 I1 --- Score [0/2] 2 = core, 1 = likely core (G1)
65- 72 A8 --- OType Source type (1)
74- 76 I3 --- IDB3 [1/256]? Source ID match from Band 3
78- 81 I4 K TB [9/1097] Brightness temperature
83- 88 F6.3 --- alpha [-1/3.7] Spectral index
90- 94 F5.3 --- e_alpha [0.002/0.4] Uncertainty on spectral index
96- 99 F4.1 Msun Mass [0.6/72.6]? Core mass
--------------------------------------------------------------------------------
Note (1): Type as follows:
core = core (90 occurrences)
HII = known hypercompact and ultracompact HII region (8 occurrences)
HII_cand = HII region candidate (9 occurrences)
HII_new = new hypercompact HII region (1 occurrence)
See Section 3.1
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4c.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/397] Source ID
5- 9 F5.2 mJy SnuF [0.04/58.1] Dendrogram contour flux
11- 15 F5.2 mJy/beam SnuPk [0.16/41.3] Brightest pixel flux
17- 21 F5.3 mJy/beam ErrSnu [0.03/0.07] Noise
23- 27 F5.3 arcsec FWHMmaj [0.03/0.3] Source FWHM (maj)
29- 33 F5.3 arcsec FWHMmin [0.019/0.3] Source FWHM (min)
35- 36 I2 h RAh [17] Hour of Right Ascension (J2000)
38- 39 I2 min RAm [47] Minute of Right Ascension (J2000)
41- 47 F7.4 s RAs [16.8/23] Second of Right Ascension (J2000)
49 A1 --- DE- [-] Sign of Declination (J2000)
50- 51 I2 deg DEd [28] Degree of Declination (J2000)
53- 54 I2 arcmin DEm [21/22] Arcminute of Declination (J2000)
56- 61 F6.3 arcsec DEs Arcsecond of Declination (J2000)
63 I1 --- Score [0/2] 2 = core, 1 = likely core (G1)
65- 72 A8 --- OType Source type (1)
74- 76 I3 --- IDG18 [96/252]? Source ID match from G18
(Ginsburg+ 2018, J/ApJ/853/171) catalog
78- 83 A6 --- OIDG18 Source OID match from G18
(Ginsburg+ 2018, J/ApJ/853/171) catalog
84- 86 I3 --- IDB6 [1/340]? Source ID match from Band 6
88- 90 I3 K TB [3/834] Brightness temperature
92- 96 F5.2 --- alpha [-1.05/4.5]? Spectral index
98- 101 F4.2 --- e_alpha [0.02/0.4]? Uncertainty on spectral index
103- 107 F5.1 Msun Mass [1/163]? Core mass
--------------------------------------------------------------------------------
Note (1): Type as follows:
core = core (203 occurrences)
HII = known hypercompact and ultracompact HII region (3 occurrences)
HII_cand = HII region candidate (4 occurrences)
HII_new = new hypercompact HII region (5 occurrences)
See Section 3.1
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4d.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/340] Source ID
5- 9 F5.1 mJy SnuF [0.8/133] Dendrogram contour flux
11- 14 F4.1 mJy/beam SnuPk [1.8/54.7] Brightest pixel flux
16- 20 F5.3 mJy/beam ErrSnu [0.3/1.2] Noise
22- 26 F5.3 arcsec FWHMmaj [0.03/0.31] Source FWHM (maj)
28- 32 F5.3 arcsec FWHMmin [0.014/0.2] Source FWHM (min)
34- 35 I2 h RAh [17] Hour of Right Ascension (J2000)
37- 38 I2 min RAm [47] Minute of Right Ascension (J2000)
40- 46 F7.4 s RAs [18.5/20.4] Second of Right Ascension (J2000)
48 A1 --- DE- [-] Sign of Declination (J2000)
49- 50 I2 deg DEd [28] Degree of Declination (J2000)
52- 53 I2 arcmin DEm [21/22] Arcminute of Declination (J2000)
55- 60 F6.3 arcsec DEs Arcsecond of Declination (J2000)
62 I1 --- Score [1/2] 2 = core, 1 = likely core (G1)
64- 71 A8 --- OType Source type (1)
73- 75 I3 --- IDB3 [2/323]? Source ID match from Band 3
77- 79 I3 K TB [13/409] Brightness temperature
81- 85 F5.2 --- alpha [-1.01/4.3] Spectral index
87- 90 F4.2 --- e_alpha [0.01/0.4] Uncertainty on spectral index
92- 95 F4.1 Msun Mass [0.8/39.7]? Core mass
--------------------------------------------------------------------------------
Note (1): Type as follows:
core = core (128 occurrences)
HII_cand = HII region candidate (3 occurrences)
HII_new = new hypercompact HII region (4 occurrences)
See Section 3.1
--------------------------------------------------------------------------------
Global notes:
Note (G1): We review each of the cataloged sources in both pointings
and frequencies by hand. We rank every source as not a core (0), core
candidate (1), or core (2). We inspect each source twice: first
zoomed-in closely to examine the shape and the background features,
and then using the whole image to get context on the source morphology
based on location and proximity to other sources. See Section 3.1.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Mar-2026