ALMA and VLA observations of recombination lines and continuum toward the Becklin-Neugebauer object in Orion

Galván-Madrid, Roberto; Goddi, C.; Rodrı́guez, Luis F.

doi:10.1051/0004-6361/201220330

Cited by 14 publications

(20 citation statements)

References 24 publications

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“…14 resolution map is roughly 2× higher than the value recently reported by Galván-Madrid et al (2012) from an analysis of ALMA Band 6 Science Verification data. These early ALMA data had a 1.…”

Section: Resultsmentioning

confidence: 49%

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The Ionized Circumstellar Envelopes of Orion Source I and the Becklin-Neugebauer Object

Plambeck

Bolatto

Carpenter

et al. 2013

ApJ

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The 229 GHz (λ1.3 mm) radio emission from Orion-KL was mapped with up to 0. 14 angular resolution with CARMA, allowing measurements of the flux densities of Source I ("SrcI") and the Becklin-Neugebauer Object (BN), the two most massive stars in this region. We find integrated flux densities of 310 ± 45 mJy for SrcI and 240 ± 35 mJy for BN. SrcI is optically thick even at 229 GHz. No trace of the H30α recombination line is seen in its spectrum, although the v 2 = 1, 5(5,0)-6(4,3) transition of H 2 O, 3450 K above the ground state, is prominent. SrcI is elongated at position angle 140 • , as in 43 GHz images. These results are most easily reconciled with models in which the radio emission from SrcI arises via the H − free-free opacity in a T < 4500 K disk, as considered by Reid et al. By contrast, the radio spectrum of BN is consistent with p + /e − free-free emission from a dense (n e ∼ 5 × 10 7 cm −3 ), but otherwise conventional, hypercompact H ii region. The source is becoming optically thin at 229 GHz, and the H30α recombination line, at V LSR = 23.2 ± 0.5 km s −1 , is prominent in its spectrum. A Lyman continuum flux of 5 × 10 45 photons s −1 , consistent with that expected from a B star, is required to maintain the ionization. Supplementary 90 GHz observations were made to measure the H41α and H42α recombination lines toward BN. Published 43 and 86 GHz data suggest that SrcI brightened with respect to BN over the 15 year period from 1994 to 2009.

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Section: Resultsmentioning

confidence: 49%

“…The BN flux density we measure with 0. 14 resolution is a factor of two greater than that derived by Galván-Madrid et al (2012) from the ALMA Science Verification data with a 1. 3 × 0.…”

Section: Discussionmentioning

confidence: 77%

The Ionized Circumstellar Envelopes of Orion Source I and the Becklin-Neugebauer Object

Plambeck

Bolatto

Carpenter

et al. 2013

ApJ

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“…Pressure broadening, which scales linearly with electron density, manifests as a Lorentzian line profile, and not a Gaussian line profile as many other broadening mechanisms do (see e.g. Keto et al 2008;Galván-Madrid et al 2012). The result of the blend of Gaussian and Lorentzian profile is a Voigt profile.…”

Section: Ionised Gasmentioning

confidence: 99%

The evolution of young HII regions

Klaassen

Johnston

Urquhart

et al. 2018

A&A

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Context. High-mass stars form in much richer environments than those associated with isolated low-mass stars, and once they reach a certain mass, produce ionised (Hii) regions. The formation of these pockets of ionised gas are unique to the formation of high-mass stars (M > 8 M ), and present an excellent opportunity to study the final stages of accretion, which could include accretion through the Hii region itself. Aims. This study of the dynamics of the gas on both sides of these ionisation boundaries in very young Hii regions aims to quantify the relationship between the Hii regions and their immediate environments. Methods. We present high-resolution (∼ 0.5 ) ALMA observations of nine Hii regions selected from the Red MSX Source (RMS) survey with compact radio emission and bolometric luminosities greater than 10 4 L . We focus on the initial presentation of the data, including initial results from the radio recombination line H29α, some complementary molecules, and the 256 GHz continuum emission. Results. Of the six (out of nine) regions with H29α detections, two appear to have cometary morphologies with velocity gradients across them, and two appear more spherical with velocity gradients suggestive of infalling ionised gas. The remaining two were either observed at low resolution or had signals that were too weak to draw robust conclusions. We also present a description of the interactions between the ionised and molecular gas (as traced by CS (J=5-4)), often (but not always) finding the Hii region had cleared its immediate vicinity of molecules. Conclusions. Of our sample of nine, the observations of the two clusters expected to have the youngest Hii regions (from previous radio observations) are suggestive of having infalling motions in the H29α emission, which could be indicative of late stage accretion onto the stars despite the presence of an Hii region.

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“…Finally, we note that the velocityintegrated line intensities for both lines are about the same. For resolved observations, and assuming LTE and low line and free-free continuum optical depths, the line ratio should scale approximately linearly with frequency (e.g., Keto et al 2008;Galván-Madrid et al 2012). Two possible explanations for our observations are that the H26α line, because its lower optical depth, has a smaller filling factor within the APEX beam than the H30α line; or that the H30α line is amplified by non-LTE effects (e.g.…”

Section: Radio-recombination Linesmentioning

confidence: 93%

Massive envelopes and filaments in the NGC 3603 star forming region

Hummel¹,

Stanke²,

Galván-Madrid³

et al. 2015

A&A

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The formation of massive stars and their arrival on the zero-age main-sequence occurs hidden behind dense clouds of gas and dust.In the giant H  region NGC 3603, the radiation of a young cluster of OB stars has dispersed dust and gas in its vicinity. At a projected distance of 2.5 pc from the cluster, a bright mid-infrared (MIR) source (IRS 9A) was identified as a massive young stellar object (MYSO), located on the side of a molecular clump (MM2) of gas facing the cluster. We investigated the physical conditions in MM2, based on APEX sub-mm observations using the SABOCA and SHFI instruments, and archival ATCA 3 mm continuum and CS spectral line data. We resolved MM2 into several compact cores, one of them closely associated with IRS 9A. These are likely to be infrared dark clouds because they do not show the typical hot-core emission lines and are mostly opaque against the MIR background. The compact cores have masses of up to several hundred times the solar mass and gas temperatures of about 50 K, without evidence of internal ionizing sources. We speculate that IRS 9A is younger than the cluster stars, but is in an evolutionary state after the compact cores.

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ALMA and VLA observations of recombination lines and continuum toward the Becklin-Neugebauer object in Orion

Cited by 14 publications

References 24 publications

The Ionized Circumstellar Envelopes of Orion Source I and the Becklin-Neugebauer Object

The Ionized Circumstellar Envelopes of Orion Source I and the Becklin-Neugebauer Object

The evolution of young HII regions

Massive envelopes and filaments in the NGC 3603 star forming region

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