J/ApJ/809/10 Compact radio sources within 30" of Sgr A* (Yusef-Zadeh+, 2015)
Compact radio sources within 30" of Sgr A*: proper motions, stellar winds, and
the accretion rate onto Sgr A*.
Yusef-Zadeh F., Bushouse H., Schodel R., Wardle M., Cotton W.,
Roberts D.A., Nogueras-Lara F., Gallego-Cano E.
<Astrophys. J., 809, 10 (2015)>
=2015ApJ...809...10Y 2015ApJ...809...10Y (SIMBAD/NED BibCode)
ADC_Keywords: Radio continuum ; Cross identifications ; Infrared sources ;
Milky Way
Keywords: accretion, accretion disks; black hole physics; Galaxy: center
Abstract:
Recent broadband 34 and 44GHz radio continuum observations of the
Galactic center have revealed 41 massive stars identified with near-IR
(NIR) counterparts, as well as 44 proplyd candidates within 30" of
SgrA*. Radio observations obtained in 2011 and 2014 have been used to
derive proper motions of eight young stars near Sgr A*. The accuracy
of proper motion estimates based on NIR observations by Lu et al.
(2009ApJ...690.1463L 2009ApJ...690.1463L) and Paumard et al. (2006, J/ApJ/643/1011) have
been investigated by using their proper motions to predict the 2014
epoch positions of NIR stars and comparing the predicted positions
with those of radio counterparts in the 2014 radio observations.
Predicted positions from Lu et al. show an rms scatter of 6mas
relative to the radio positions, while those from Paumard et al. show
rms residuals of 20mas. We also determine the mass-loss rates of 11
radio stars, finding rates that are on average ∼2 times smaller than
those determined from model atmosphere calculations and NIR data.
Clumpiness of ionized winds would reduce the mass loss rate of WR and
O stars by additional factors of 3 and 10, respectively. One important
implication of this is a reduction in the expected mass accretion rate
onto Sgr A* from stellar winds by nearly an order of magnitude to a
value of a few x10-7m☉/yr. Finally, we present the positions
of 318 compact radio sources within 30" of Sgr A*, 45 of which have
stellar counterparts in the NIR Ks (2.18µm) and L' (3.8µm)
bands.
Description:
We obtained two sets of A-array observations with the Karl G. Jansky
Very Large Array (VLA).
The first set of observations of the stellar cluster at the Galactic
center were obtained on 2011 July 8-9 and 2011 August 31-September 1
at 44GHz (program 11A-224). Further details of these first-epoch
observations are given in Yusef-Zadeh et al. (2014ApJ...792L...1Y 2014ApJ...792L...1Y).
We reobserved the region within 30" of Sgr A* on 2014 February 21,
again using the VLA in its A-configuration at 44GHz.
We also carried out A-array observations (program 14A-232) in the Ka
(9mm) band on 2014 March 9 at 34.5GHz.
We searched for NIR counterparts to compact radio sources using
high-angular resolution AOs assisted imaging observations acquired
with the VLT/NACO (NAos-COnica). A Ks-band (central wavelength 2.18um)
image was obtained in a rectangular dither pattern on 2012 September
12. L'-band (3.8um) observations were obtained during various
observing runs between 2012 June and September.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table6.dat 139 318 Gaussian fitted parameters of 34.5GHz continuum
sources within 30" of Sgr A*
--------------------------------------------------------------------------------
See also:
J/A+A/566/A47 : MW nuclear star cluster extinction map (Schoedel+, 2014)
J/ApJ/725/331 : Astrometry in the Galactic Center (Yelda+, 2010)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/ApJ/707/L114 : The orbit of S2 star around Sgr A* (Gillessen+, 2009)
J/ApJ/659/1241 : Stellar variability in Galactic Center (Rafelski+, 2007)
J/ApJ/643/1011 : Early-type stars in the center of the Galaxy (Paumard+, 2006)
J/A+A/433/117 : L- + M-band imaging of the Galactic Center (Viehmann+, 2005)
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/318] Running sequence number of
the radio source
5- 17 A13 --- AName NIR identified stellar source
19- 20 I2 h RAh Hour of right ascension (J2000)
22- 23 I2 min RAm Minute of right ascension (J2000)
25- 31 F7.4 s RAs Second of right ascension (J2000)
33 A1 --- DE- Sign of declination (J2000)
34- 35 I2 deg DEd Degree of declination (J2000)
37- 38 I2 arcmin DEm Arcminute of declination (J2000)
40- 46 F7.4 arcsec DEs Arcsecond of declination (J2000)
48- 52 F5.2 arcsec Sep [0/33.4] Angular distance from Sgr A*
54- 59 F6.2 mas PosErr [0/220.2] Positional precision
61- 65 I5 mas amaj [4/10330]? Deconvolved source major axis size
θa
66 A1 --- --- [x]
67- 69 I3 mas amin [0/375]? Deconvolved source minor axis size
θb
71- 73 I3 deg PA ? Deconvolved source position angle
75- 82 F8.3 mJy/beam Pk [0.02/1720] 34.5GHz peak radio intensity
84- 88 F5.3 mJy/beam e_Pk [0.003/0.02] IPk uncertainty
90- 97 F8.3 mJy Flux [0/1723] 34.5GHz integrated flux
99-103 F5.3 mJy e_Flux [0.001/0.6] Flux uncertainty
105-110 F6.2 mJy FKs [0.02/149]? VLT/NACO Ks (2.18um) flux density
112-116 F5.3 mJy e_FKs [0.001/8]? FKs uncertainty
118-124 F7.2 mJy FL' [0.07/1253]? VLT/NACO L' (3.8um) flux density
126-131 F6.3 mJy e_FL' [0.004/66]? FL' uncertainty
133-139 A7 --- Comm References and comments on individual
source (1)
--------------------------------------------------------------------------------
Note (1): References and comments as follows:
1 = Viehmann et al. (2005, J/A+A/433/117),
2 = Eckart et al. (2004ApJ...602..760E 2004ApJ...602..760E),
3 = Paumard et al. (2006, J/ApJ/643/1011),
4 = Moultaka et al. (2009ApJ...703.1635M 2009ApJ...703.1635M),
5 = Yusef-Zadeh et al. (2014ApJ...792L...1Y 2014ApJ...792L...1Y).
a = Detected only in L';
b = Detected only in Ks and faint source;
c = Consists of multiple radio components.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 05-Apr-2016