Query : 2009ApJ...703.1832H

2009ApJ...703.1832H - Astrophys. J., 703, 1832-1838 (2009/October-1)

Ionized gas in the Smith Cloud.


Abstract (from CDS):

We present Wisconsin Hα Mapper observations of ionized gas in the Smith Cloud, a high-velocity cloud which Lockman et al. have recently suggested is interacting with the Galactic disk. Our Hα map shows the brightest Hα emission, 0.43±0.04 R, coincident with the brightest H I, while slightly fainter Hα emission (0.25±0.02 R) is observed in a region with H I intensities <0.1 times as bright as the brightest H I. We derive an ionized mass of ≳3x106 M, comparable to the H I mass, with the H+ mass spread over a considerably larger area than that of H I. An estimated Galactic extinction correction could adjust these values upward by 40%. Hα and [S II] line widths toward the region of brightest emission constrain the electron temperature of the gas to be between 8000 K and 23,000 K. A detection of [N II] λ6583 in the same direction with a line ratio [N II]/Hα = 0.32±0.05 constrains the metallicity of the cloud: for typical photoionization temperatures of 8000-12,000 K, the nitrogen abundance is 0.15-0.44 times solar. These results lend further support to the claim that the Smith Cloud is new material accreting onto the Galaxy.

Abstract Copyright:

Journal keyword(s): Galaxy: evolution - Galaxy: halo - ISM: abundances - ISM: clouds - ISM: individual: Smith Cloud

Nomenclature: Fig. 3, Table 2: [HHR2009] Clump A (Nos A-B), [HHR2009] Tip N=1, [HHR2009] Tail N=1.

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 [H68] K HVC 09 47 -27.0           ~ 20 0
2 [H68] L HVC 15 06.4 -15 30           ~ 17 0
3 NAME HVC Complex C HVC 16 34.8 +63 07           ~ 242 1
4 NAME Gal Center Positive HVC 20 51.2 +01 41           ~ 87 1

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