J/ApJ/801/L26 Parameters of radio sources near Sgr A* (Yusef-Zadeh+, 2015)
Radio continuum observations of the Galactic center: photoevaporative
proplyd-like objects near Sgr A*.
Yusef-Zadeh F., Roberts D.A., Wardle M., Cotton W., Schodel R.,
Royster M.J.
<Astrophys. J., 801, L26 (2015)>
=2015ApJ...801L..26Y 2015ApJ...801L..26Y (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Radio sources ; Stars, distances
Keywords: Galaxy: center - H II regions - ISM: general - radio continuum: ISM -
stars: protostars
Abstract:
We present radio images within 30" of Sgr A* based on recent VLA
observations at 34 GHz with 7.8 µJy sensitivity and resolution of
∼88x46 mas. We report 44 partially resolved compact sources
clustered in two regions in the E arm of ionized gas that orbits Sgr A*.
These sources have size scales ranging between ∼50 and 200 mas
(400-1600 AUs), and a bow-shock appearance facing the direction of
Sgr A*. Unlike the bow-shock sources previously identified in the
near-IR but associated with massive stars, these 34 GHz sources do not
appear to have near-IR counterparts at 3.8 µm. We interpret these
sources as a candidate population of photoevaporative protoplanetary
disks (proplyds) that are associated with newly formed low mass stars
with mass loss rates ∼10-7-10-6 M☉/yr and are located at
the edge of a molecular cloud outlined by ionized gas. The disks are
externally illuminated by strong Lyman continuum radiation from the
∼100 OB and WR massive stars distributed within 10" of Sgr A*. The
presence of proplyds implies current in situ star formation activity
near Sgr A* and opens a window for the first time to study low mass
star, planetary, and brown dwarf formations near a supermassive black
hole. The video abstract was created from a WorldWide Telescope tour
file, which is available for download. Viewing the file requires a
Windows PC with the WorldWide Telescope desktop client available at
worldwidetelescope.org.
Description:
Radio continuum observations were carried out with the Karl G. Jansky
Very Large Array (VLA) in its A-configuration at 34.5 GHz on 2014
March 9 (14A-232). We observed a field of view with a radius of 39''
centered on Sgr A* in the Ka band (8.7 mm) using the 3 bit sampler
system, which provided full polarization correlations in four
basebands, each 2 GHz wide, centered at 31.5, 33.5, 35.5, and 37.5 GHz.
Each baseband was composed of 16 subbands 128 MHz wide. Each subband
was composed of 64 channels, each 2 MHz wide.
Objects:
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RA (ICRS) DE Designation(s)
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17 45 40.04 -29 00 28.2 Sgr A* = NAME Sagittarius A
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 44 The Parameters of Gaussian Fitted 34 GHz Sources
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See also:
J/ApJ/699/186 : VLA observations of the Galactic center (Zhao+, 2009)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Detected radio source identifier
([YRW2015] PNN in Simbad)
4 A1 --- n_ID [a] Note on ID (1)
6- 7 I2 h RAh Hour of Right Ascension (J2000)
9- 10 I2 min RAm Minute of Right Ascension (J2000)
12- 18 F7.4 s RAs Second of Right Ascension (J2000)
20 A1 --- DE- Sign of the Declination (J2000)
21- 22 I2 deg DEd Degree of Declination (J2000)
24- 25 I2 arcmin DEm Arcminute of Declination (J2000)
27- 33 F7.4 arcsec DEs Arcsecond of Declination (J2000)
35- 39 F5.2 arcsec Dist Distance from Sgr A*
41- 45 F5.2 mas epos Positional accuracy
47- 49 I3 mas theta-a Semi-major axis
51- 53 I3 mas theta-b Semi-minor axis
55- 57 I3 deg PA Position angle
59- 63 F5.3 mJy/beam PInt Peak intensity
65- 69 F5.3 mJy/beam e_PInt Uncertainty in PInt
71- 75 F5.3 mJy Sint Integrated flux at 34 GHz
77- 81 F5.3 mJy e_Sint Uncertainty in Sint
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Note (1): Note as follows:
a = Spatially unresolved in one direction.
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History:
From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 11-Sep-2017