Evolution of H<scp>ii</scp>Regions inside Hot Molecular Cores

González-Avilés, Mauricio; Lizano, Susana; Raga, A. C.

doi:10.1086/427470

Cited by 11 publications

(9 citation statements)

References 42 publications

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“…Additional observations of very high angular resolution are needed to test the nature of this source as a hypercompact H ii region. Hypercompact H ii regions are thought to mark the earliest stages of evolution of regions of ionized gas, being formed in the accretion phase of hot molecular cores (Keto 2002(Keto , 2003González-Avilés et al 2005;Avalos et al 2006). We conclude that IRAS 23151+5912 is indeed associated with a massive-star-forming region in a very early stage of evolution.…”

Section: Iras 23151+5912mentioning

confidence: 73%

Very Large Array Observations of Candidate High-Mass Protostellar Objects at 7 Millimeters

2007

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We present radio-continuum observations at 7 mm made using the Very Large Array toward three massive starforming regions thought to be in very early stages of evolution, selected from the 2002 sample of Sridharan et al. Emission was detected toward all three sources (IRAS 18470À0044, IRAS 19217+1651, and IRAS 23151+5912). We find that in all cases the 7 mm emission corresponds to thermal emission from ionized gas. The regions of ionized gas associated with IRAS 19217+1651 and IRAS 23151+5912 are hypercompact, with diameters of 0.009 and 0.0006 pc and emission measures of 7:0 ; 10 8 and 2:3 ; 10 9 pc cm À6 , respectively.

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Section: Iras 23151+5912mentioning

confidence: 73%

Very Large Array Observations of Candidate High-Mass Protostellar Objects at 7 Millimeters

2007

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“…The predicted evolutionary timescales are long enough to make the trapped phase of an HII region much more easily observable than the following, rapid expansion phase. A recent model by González-Avilés et al (2005) , studying the evolution of an HII region inside an accreting hot molecular core, indicates that the HII region expands to a size of ∼ 500 AU in only a few hundreds of years.…”

Section: Association and Kinematics Of Methanol And Water Masers In A...mentioning

confidence: 99%

Associations of H₂O and CH₃OH masers at milli-arcsec angular resolution in two high-mass YSOs

Goddi¹,

Moscadelli

Sanna

et al. 2006

A&A

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Context. While high-angular resolution observations have clarified that water masers originate from shocks associated with protostellar jets, different environments have been proposed in several sources to explain the origin of CH 3 OH masers. Aims. We wish to investigate the nature of the CH 3 OH maser birthplace in SFRs and the association between the H 2 O and CH 3 OH maser emission in the same YSO. Methods. We have conducted phase-reference VLBI observations of H 2 O and CH 3 OH masers toward two high-mass SFRs, Sh 2-255 IR and AFGL 5142. Results. In Sh 2-255 IR water masers are aligned along a direction close to the orientation of the molecular outflow observed on angular scales of 1-10 arcsec, tracing possibly the disk-wind emerging from the disk atmosphere. In AFGL 5142 water masers trace expansion at the base of a protostellar jet, whilst methanol masers are more probably tracing infalling than outflowing gas. Conclusions. The results for AFGL 5142 suggest that water and methanol masers trace different kinematic structures in the circumstellar gas.

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“…The suppression of the conduction rate by magnetic fields wrapping the bubble needs to be considered for this model as in clusters of galaxies and supernova remnants (e.g., Malyshkin 2001;Velázquez et al 2004). González-Avilés et al (2005) calculated the bubble temperature for different conduction rates ( / c , where c is the classical value) and found that the temperature under a conduction rate of / c < 1/5 is lower than that under the adiabatic case ( / c ¼ 0) by only a factor of a few. Under such conditions, the wind-blown bubble model can probably account for the observed high plasma temperature.…”

Section: Wind-blown Bubblementioning

confidence: 99%

Hard X‐Rays from Ultracompact HiiRegions in W49A

Tsujimoto

Hosokawa

Feigelson

et al. 2006

ApJ

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We report the Chandra detection of hard X-ray emission from the Welch ring in W49A, an organized structure of ultracompact (UC ) H ii regions containing a dozen nascent early-type stars. Two UC H ii regions are associated with hard X-ray emission in a deep Advanced CCD Imaging Spectrometer (ACIS) image exposed for $96.7 ks. One of the two X-ray sources has no near-infrared counterpart and is extended by $5 00 , or $0.3 pc, at a distance of $11.4 kpc, which is spatially aligned with the cometary radio continuum emission associated with the UC H ii region. The X-ray spectrum of the emission, when fit with a thermal model, indicates a heavily absorbed plasma with extinction of $5 ; 10 23 cm À2 , temperature $7 keV, and X-ray luminosity in the 3.0Y8.0 keV band of $3;10 33 ergs s À1 . Both the luminosity and the size of the emission resemble the extended hard emission found in UC H ii regions in Sagittarius B2, yet they are smaller by an order of magnitude than the emission found in massive star clusters such as NGC 3603. Three possibilities are discussed for the cause of the hard extended emission in the Welch ring: an ensemble of unresolved point sources, shocked interacting winds of the young O stars, and a wind-blown bubble interacting with ambient cold matter. Subject headingg s: H ii regions -ISM: individual ( W49A) -radio continuum: ISM -stars: early-type -X-rays: ISM

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Evolution of HiiRegions inside Hot Molecular Cores

Cited by 11 publications

References 42 publications

Very Large Array Observations of Candidate High-Mass Protostellar Objects at 7 Millimeters

Very Large Array Observations of Candidate High-Mass Protostellar Objects at 7 Millimeters

Associations of H₂O and CH₃OH masers at milli-arcsec angular resolution in two high-mass YSOs

Hard X‐Rays from Ultracompact HiiRegions in W49A

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Evolution of HiiRegions inside Hot Molecular Cores

Cited by 11 publications

References 42 publications

Very Large Array Observations of Candidate High-Mass Protostellar Objects at 7 Millimeters

Very Large Array Observations of Candidate High-Mass Protostellar Objects at 7 Millimeters

Associations of H2O and CH3OH masers at milli-arcsec angular resolution in two high-mass YSOs

Hard X‐Rays from Ultracompact HiiRegions in W49A

Contact Info

Product

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Associations of H₂O and CH₃OH masers at milli-arcsec angular resolution in two high-mass YSOs