TY - JOUR
T1 - Proper motions of ionized gas at the galactic center
T2 - Evidence for unbound orbiting gas
AU - Yusef-Zadeh, F.
AU - Roberts, D. A.
AU - Blretta, J.
N1 - Funding Information:
1 The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.
Funding Information:
The work of F. Y.-Z. was supported in part by NASA grant NAGW-2518. D. R. acknowledges support from the NSF grant AST94-19227. We thank Mark Wardle for useful discussion.
PY - 1998
Y1 - 1998
N2 - We present radio continuum observations of the spiral-shaped ionized feature (Sgr A West) within the inner parsec of the Galactic center at three epochs spanning 1986 to 1995. The Very Large Array A configuration was used at X = 2 cm (resolution of ″1 × 0″2). We detect proper motions of a number of features in the northern and eastern arms of Sgr A West including the ionized gas associated with 1RS 13 with V(R.A.) = 113 ±10 and V(decl.) = 150 ±15 km s-1, 1RS 2 with V(R.A.) = 122 ±11 and V(decl.) = 24 ±34 km s-1, and the northern arm with V(R.A.) = 126 ±30 and V(decl.) = -207 ±58 km s-1. We also report the detection of features having transverse velocities greater than 1000 km s~', including a head-tail radio structure, the "bullet, " ≈4″ northwest of Sgr A* with V(R.A.) = 722 ±156, V(decl.) = 832 ±203 km s-1, exceeding the escape velocity at the Galactic center. The proper-motion measurements, when combined with previous H92α radio recombination line data, suggest an unambiguous direction of the flow of ionized gas orbiting the Galactic center. The measured velocity distribution suggests that the ionized gas in the northern arm is not bound to the Galactic center assuming 2.5 ′ 106 M⊙ of dark matter residing at the Galactic center. This implies that the stellar and ionized gas systems are not dynamically coupled, thus supporting a picture in which the gas features in the northern arm and its extensions are the result of an energetic phenomenon that has externally driven a cloud of gas into the Galactic center.
AB - We present radio continuum observations of the spiral-shaped ionized feature (Sgr A West) within the inner parsec of the Galactic center at three epochs spanning 1986 to 1995. The Very Large Array A configuration was used at X = 2 cm (resolution of ″1 × 0″2). We detect proper motions of a number of features in the northern and eastern arms of Sgr A West including the ionized gas associated with 1RS 13 with V(R.A.) = 113 ±10 and V(decl.) = 150 ±15 km s-1, 1RS 2 with V(R.A.) = 122 ±11 and V(decl.) = 24 ±34 km s-1, and the northern arm with V(R.A.) = 126 ±30 and V(decl.) = -207 ±58 km s-1. We also report the detection of features having transverse velocities greater than 1000 km s~', including a head-tail radio structure, the "bullet, " ≈4″ northwest of Sgr A* with V(R.A.) = 722 ±156, V(decl.) = 832 ±203 km s-1, exceeding the escape velocity at the Galactic center. The proper-motion measurements, when combined with previous H92α radio recombination line data, suggest an unambiguous direction of the flow of ionized gas orbiting the Galactic center. The measured velocity distribution suggests that the ionized gas in the northern arm is not bound to the Galactic center assuming 2.5 ′ 106 M⊙ of dark matter residing at the Galactic center. This implies that the stellar and ionized gas systems are not dynamically coupled, thus supporting a picture in which the gas features in the northern arm and its extensions are the result of an energetic phenomenon that has externally driven a cloud of gas into the Galactic center.
KW - Galaxies: ISM
KW - Galaxy: center
KW - ISM: individual (Sagittarius A East, Sagittarius A West)
KW - ISM: magnetic fields
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M3 - Article
AN - SCOPUS:22044446329
SN - 0004-637X
VL - 499
SP - L159-L162
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 PART II
ER -