Radio observations of new galactic bulge planetary nebulae

Steene, G. C. Van de; Jacoby, George H.

doi:10.1051/0004-6361:20010306

Cited by 54 publications

(77 citation statements)

References 15 publications

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“…All the three 4.5 μm excess sources g1, g2, and g4 are located at the edge of the region surveyed with IRAC. Sources g1, g4, and g2 coincide with the positions of three PNe JaST 76 and JaST 70 in Van de Steene & Jacoby (2001) and PN G0.8−0.6 in Kerber et al (2003), respectively. The SEDs of these sources are shown in Figure 16(b).…”

Section: A1 Galactic Center 45 μM Excess Sourcesmentioning

confidence: 69%

Star Formation in the Central 400 Pc of the Milky Way: Evidence for a Population of Massive Young Stellar Objects

Yusef‐Zadeh

Hewitt

Arendt

et al. 2009

ApJ

204

264

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The central kpc of the Milky Way might be expected to differ significantly from the rest of the Galaxy with regard to gasdynamics and the formation of young stellar objects (YSOs). We probe this possibility with midinfrared observations obtained with Infrared Array Camera and Multiband Imaging Photometer on Spitzer and with Midcourse Space Experiment. We use color-color diagrams and spectral energy distribution (SED) fits to explore the nature of YSO candidates (including objects with 4.5 μm excesses possibly due to molecular emission). There is an asymmetry in the distribution of the candidate YSOs, which tend to be found at negative Galactic longitudes; this behavior contrasts with that of the molecular gas, approximately 2/3 of which is at positive longitudes. The small-scale height of these objects suggests that they are within the Galactic center region and are dynamically young. They lie between two layers of infrared dark clouds and may have originated from these clouds. We identify new sites for this recent star formation by comparing the mid-IR, radio, submillimeter, and methanol maser data. The methanol masers appear to be associated with young, embedded YSOs characterized by 4.5 μm excesses. We use the SEDs of these sources to estimate their physical characteristics; their masses appear to range from ∼10 to ∼20 M . Within the central 400 × 50 pc (|l| < 1.• 3 and |b| < 10 ) the star formation rate (SFR) based on the identification of Stage I evolutionary phase of YSO candidates is about 0.14 M yr −1 . Given that the majority of the sources in the population of YSOs are classified as Stage I objects, we suggest that a recent burst of star formation took place within the last 10 5 yr. This suggestion is also consistent with estimates of SFRs within the last ∼10 7 yr showing a peak around 10 5 yr ago. Lastly, we find that the Schmidt-Kennicutt Law applies well in the central 400 pc of the Galaxy. This implies that star formation does not appear to be dramatically affected by the extreme physical conditions in the Galactic center region.

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Section: A1 Galactic Center 45 μM Excess Sourcesmentioning

confidence: 69%

Star Formation in the Central 400 Pc of the Milky Way: Evidence for a Population of Massive Young Stellar Objects

Yusef‐Zadeh

Hewitt

Arendt

et al. 2009

ApJ

204

264

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“…4 for circular and elliptical PNe. Because the differing statistical scales are linearly related (Phillips 2002b), one expects very closely similar trends to arise for the distances of Zhang (1995), van de Steene & Zijlstra (1994), Cahn et al (1992) and Daub (1982). The solid curve corresponds to a second order least squares polynomial fit.…”

Section: This Increase In Velocities (V Exp ([Nii]) Over V Exp ([Oiiimentioning

confidence: 84%

The correlation between expansion velocity and morphology in planetary nebulae

Phillips¹

2002

A&A

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Abstract. It is usually accepted that the differing morphological classes of planetary nebulae (PNe) arise from progenitors of differing mass. The primary evidence for this derives from the differing galactic distributions of the sources. This, if true, would be expected to result in other differences as well, including variations in the kinematics of the nebular envelopes. We point out here that there is now sufficient evidence to determine that this is the case. We find that BRET-type sources (i.e. nebulae possessing "bipolar rotating episodic jets") have the lowest velocities of expansion V EXP , followed (in order of increasing velocity) by bipolar (BPNe), elliptical and circular nebulae. In addition to this, we find that the distributions N(V EXP ) of circular, elliptical and bipolar sources are quite distinct, with BPNe being biased towards lower velocities, and circular sources distributed more uniformly. It appears therefore that bipolar outflows contain, within the same shells, evidence for both the highest and lowest velocities of expansion. Whilst the outer wings of these nebulae are expanding at ∼175 km s −1 , the brighter parts of the shells (probably corresponding to equatorial toroids) have velocities of only ∼18 km s −1 .

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“…To answer the first question, we note that a comparison of the Zhang distances with those of van de Steene & Zijlstra (1994) indicates a linear relation between the two sets of data, with very small level of scatter (Zhang 1995). We have, for the purposes of this analysis, further extended this comparison to the distances of Cahn et al (1992) and Daub (1982).…”

Section: Influence Of Distance Scales Upon Scale Heightsmentioning

confidence: 86%

“…Thus, and as will be discussed more fully in § 3, the distance scales of van de Steene & Zijlstra (1994), Cahn, Kaler, & Stanghellini (1992), Daub (1982), and others all differ from each other, and such differing scales might be expected to lead to varying scale heights.…”

Section: Evaluation Of Scale Heights For Planetary Nebulaementioning

confidence: 94%

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The Masses of the Progenitors of Planetary Nebulae

Phillips

2001

PUBL ASTRON SOC PAC

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ABSTRACT. Bipolar, elliptical, and circular planetary nebulae appear to be possessed of differing Galactic scale heights, a feature which is usually assumed to arise from the differing distributions and masses of their progenitor stars. It would appear that more massive progenitors are responsible for bipolar sources, whilst the least massive progenitors give rise to circular sources. This, clearly, is an important result, since it implies that shell formation mechanisms must be closely intertwined with progenitor type. We point out, however, that previous estimates of nebular scale height are at best somewhat sketchy and may even be wrong. At least two prior analyses, for instance, appear to compare reddened values of nebular scale height with extinction-corrected stellar scale heights. We have therefore attempted, in the following, to undertake a dereddening of nebular scale heights and perform a fresh comparison of these results with those for Galactic stars of differing spectral types. We find that circular and elliptical sources are likely to originate from early F-type stars and bipolar sources from stars of spectral type A7 or earlier. The results appear to be insensitive to uncertainties in the distance scale.

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Radio observations of new galactic bulge planetary nebulae

Cited by 54 publications

References 15 publications

Star Formation in the Central 400 Pc of the Milky Way: Evidence for a Population of Massive Young Stellar Objects

Star Formation in the Central 400 Pc of the Milky Way: Evidence for a Population of Massive Young Stellar Objects

The correlation between expansion velocity and morphology in planetary nebulae

The Masses of the Progenitors of Planetary Nebulae

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