Far-infrared lines from H II regions: Abundance variations in the galaxy

Simpson, Janet P.; Colgan, Sean W. J.; Rubin, R. H.; Erickson, E. F.; Haas, Michael R.

doi:10.1086/175645

Cited by 148 publications

(215 citation statements)

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“…The best-fit iron abundance of 5 times solar is extremely large, but within the large error, it is consistent with that of the Sgr B2 cloud of 2-3 estimated from X-ray reflection nebula (Murakami et al 2001) and that predicted from the abundance gradient of H ii regions toward the GC (e.g., Simpson et al 1995). The abundances, on the other hand, are significantly larger than that of any other highmass SFRs (Kohno et al 2002;Schulz et al 2001;Yamauchi et al 1996).…”

Section: X-rays Associated With the H II Complexessupporting

confidence: 80%

X‐Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed withChandra

Takagi

Murakami

Koyama

2002

ApJ

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We report the X-ray population study in the giant molecular cloud Sagittarius B2 (Sgr B2). More than a dozen X-ray cloud members (and candidates) are discovered with Chandra. Two bright X-ray sources are located near Sgr B2 Main, the most copious complex of the ultracompact H ii sources. The X-ray spectra are fitted with a thin thermal plasma model of 5-10 keV temperature. The intrinsic luminosity, after correcting the absorption of~5 Â 10 23 H cm À2 , is $10 33 ergs s À1 . Although these two X-ray sources are attributable to young stellar objects (YSOs) in the same H ii complex, they are in sharp contrast; the one at the center of the H ii complex exhibits strong K-shell transition lines of iron, while the other near the east has only weak lines. The other H ii complexes, Sgr B2 North and South, also show hard and highly absorbed X-ray emissions due possibly to the star formation activity. The composite X-ray spectrum of the other cloud member X-ray sources is fitted with a thin thermal plasma of $10 keV temperature with hydrogen column density (N H ) of 1:3 Â 10 23 H cm À2 and individual X-ray luminosity of a few times 10 31 -10 32 ergs s À1 . These are likely to be a single YSO or cluster of YSOs, but neither radio nor infrared counterpart is found. An alternative scenario of isolated white dwarfs powered by Bondi-Hoyle accretion from the dense cloud gas is also discussed. The X-ray spectra exhibit an additional 6.4 keV line of neutral or low-ionization irons, which indicates that the environment gas is concentrated near the sources.

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Section: X-rays Associated With the H II Complexessupporting

confidence: 80%

X‐Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed withChandra

Takagi

Murakami

Koyama

2002

ApJ

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“…3 include the recent cepheid results from Andrievsky et al (2002), shown as open circles, and H II regions from the optical emission lines analyzed by Deharveng et al (2000), shown as six-pointed stars, and H II region far-IR fine-structure lines by Simpson et al (1995) and Afflerbach et al (1997), shown as three-pointed stars.…”

Section: Discussionmentioning

confidence: 99%

“…Abundances for cepheids (Andrievsky et al 2002) are shown as open circles. The abundances for H II regions are represented by six-pointed stars (Deharveng et al 2000), and three-pointed stars (Simpson et al 1995;Afflerbach et al 1997). …”

Section: Discussionmentioning

confidence: 99%

Non-LTE abundances of magnesium, aluminum and sulfur in OB stars near the solar circle

Daflon

Cunha

Smith

et al. 2003

A&A

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Abstract. Non-LTE abundances of magnesium, aluminum and sulfur are derived for a sample of 23 low-v sin i stars belonging to six northern OB associations of the Galactic disk within 1 kpc of the Sun. The abundances are obtained from the fitting of synthetic line profiles to high resolution spectra. A comparison of our results with HII region abundances indicates good agreement for sulfur while the cepheid abundances are higher. The derived abundances of Mg show good overlap with the cepheid results. The aluminum abundances for OB stars are significantly below the cepheid values. But, the OB star results show a dependence with effective temperature and need further investigation. The high Al abundances in the cepheids could be the result of mixing. A discussion of the oxygen abundance in objects near the solar circle suggests that the current mean galactic oxygen abundance in this region is 8.6-8.7 and in agreement with the recently revised oxygen abundance in the solar photosphere. Meaningful comparisons of the absolute S, Al and Mg abundances in OB stars with the Sun must await a reinvestigation of these elements with 3D hydrodynamical model atmospheres for the Sun. No abundance gradients are found within the limited range in galactocentric distances in the present study. Such variations would be expected only if there were large metallicity gradients in the disk.

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“…3) Studies of the abundance gradient (primarily nitrogen, oxygen, sulphur) in the Galactic disc based on young objects such as H ii regions give positive results: either significant slopes from −0.07 to −0.11 dex kpc −1 according to : Shaver et al (1983) for nitrogen and oxygen, Simpson et al (1995) for nitrogen and sulphur, Afflerbach et al (1997) for nitrogen, Rudolph et al (1997) for nitrogen and sulphur, or intermediate gradients of about −0.05 to −0.06 dex kpc −1 according to : Simpson & Rubin (1990) for sulphur, Afflerbach et al (1997) for oxygen and sulphur; and negative ones: weak or nonexistent gradients as concluded by Fich & Silkey (1991); Vilchez & Esteban (1996), Rodriguez (1999). Recently Peña et al (2000) derived oxygen abundances in several H ii regions and found a rather flat distribution with galactocentric distance (coefficient −0.04 dex kpc −1 ).…”

Section: Introductionmentioning

confidence: 99%

Using Cepheids to determine the galactic abundance gradient

Andrievsky¹,

Kovtyukh

Luck

et al. 2002

A&A

188

138

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Abstract.A number of studies of abundance gradients in the galactic disk have been performed in recent years. The results obtained are rather disparate: from no detectable gradient to a rather significant slope of about −0.1 dex kpc −1 . The present study concerns the abundance gradient based on the spectroscopic analysis of a sample of classical Cepheids. These stars enable one to obtain reliable abundances of a variety of chemical elements. Additionally, they have well determined distances which allow an accurate determination of abundance distributions in the galactic disc. Using 236 high resolution spectra of 77 galactic Cepheids, the radial elemental distribution in the galactic disc between galactocentric distances in the range 6-11 kpc has been investigated. Gradients for 25 chemical elements (from carbon to gadolinium) are derived. The following results were obtained in this study. Almost all investigated elements show rather flat abundance distributions in the middle part of galactic disc. Typical values for iron-group elements lie within an interval from ≈−0.02 to ≈−0.04 dex kpc −1 (in particular, for iron we obtained d[Fe/H]/dRG = −0.029 dex kpc −1 ). Similar gradients were also obtained for O, Mg, Al, Si, and Ca. For sulphur we have found a steeper gradient (−0.05 dex kpc −1 ). For elements from Zr to Gd we obtained (within the error bars) a near to zero gradient value. This result is reported for the first time. Those elements whose abundance is not expected to be altered during the early stellar evolution (e.g. the iron-group elements) show at the solar galactocentric distance [El/H] values which are essentially solar. Therefore, there is no apparent reason to consider our Sun as a metal-rich star. The gradient values obtained in the present study indicate that the radial abundance distribution within 6-11 kpc is quite homogeneous, and this result favors a galactic model including a bar structure which may induce radial flows in the disc, and thus may be responsible for abundance homogenization.

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Far-infrared lines from H II regions: Abundance variations in the galaxy

Cited by 148 publications

References 0 publications

X‐Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed withChandra

X‐Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed withChandra

Non-LTE abundances of magnesium, aluminum and sulfur in OB stars near the solar circle

Using Cepheids to determine the galactic abundance gradient

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