Search for Ionized Jets Toward High-Mass Young Stellar Objects

Guzmán, Andrés E.; Garay, Guido; Brooks, Kate; Voronkov, Maxim

doi:10.1088/0004-637x/753/1/51

Cited by 55 publications

(72 citation statements)

References 61 publications

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“…This could be due to the influence of contamination by nearby Hii regions. Nevertheless, N73 is not only associated with a bright WISE 22 µm and unresolved radio continuum sources but is also coincident with an ionized outflow candidate reported by Guzmán et al (2012). The ionized outflow candidate was explained to be an optically thick, expanding HC Hii (Purser et al 2016).…”

Section: Potential Young Hii Regionsmentioning

confidence: 56%

ATLASGAL-selected massive clumps in the inner Galaxy

Kim

Wyrowski

Urquhart

et al. 2017

A&A

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Aims. Observations of millimeter wavelength radio recombination lines (mm-RRLs) are used to search for Hii regions in an unbiased way that is complementary to many of the more traditional methods previously used (e.g., radio continuum, far-infrared colors, maser emission). The mm-RRLs can be used to derive physical properties of Hii regions and to provide velocity information of ionized gas. Methods. We carried out targeted mm-RRL observations (39 ≤ principal quantum number (n) ≤ 65 and ∆n = 1, 2, 3, and 4, named Hnα, Hnβ, Hnγ, and Hnδ) using the IRAM 30m and Mopra 22m telescopes. In total, we observed 976 compact dust clumps selected from a catalog of ∼10,000 sources identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The sample was selected to ensure a representative mix of star-forming and quiescent clumps such that a variety of different evolutionary stages is represented. Approximately half of the clumps are mid-infrared quiet while the other half are mid-infrared bright. Results. We detected Hnα mm-RRL emission toward 178 clumps; Hnβ, Hnγ, and Hnδ were also detected toward 65, 23, and 22 clumps, respectively. This is the largest sample of mm-RRLs detections published to date. Comparing the positions of these clumps with radio continuum surveys we identified compact radio counterparts for 134 clumps, confirming their association with known Hii regions. The nature of the other 44 detections is unclear, but 8 detections are thought to be potentially new Hii regions while the mm-RRL emission from the others may be due to contamination from nearby evolved Hii regions. Broad linewidths are seen toward nine clumps (linewidth > 40 km s −1 ) revealing significant turbulent motions within the ionized gas; in the past, such wide linewidths were found toward very compact and dense Hii regions. We find that the systemic velocity of the associated dense molecular gas, traced by H 13 CO + (1−0), is consistent with the mm-RRL velocities and confirms them as embedded Hii regions. We also find that the linewidth of the H 13 CO + (1−0) emission is significantly wider than those without mm-RRL detection, indicating a physical connection between the embedded Hii region and their natal environments. We also find a correlation between the integrated fluxes of the mm-RRLs and the 6 cm continuum flux densities of their radio counterparts (the correlation coefficient, ρ, is 0.70). By calculating the electron densities we find that the mm-RRL emission is associated with Hii regions with n e <10 5 cm −3 and Hii region diameter > 0.03 pc. Conclusions. We detected mm-RRLs toward 178 clumps and identified eight new Hii region candidates. The broad mm-RRL from nine clumps may indicate that they arise in very young hyper-compact Hii regions. The mm-RRLs trace the radio continuum sources detected by high-resolution observations and their line parameters show associations with the embedded radio sources and their parental molecular clumps.

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Section: Potential Young Hii Regionsmentioning

confidence: 56%

ATLASGAL-selected massive clumps in the inner Galaxy

Kim

Wyrowski

Urquhart

et al. 2017

A&A

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“…The luminosities of these sources are estimated with the far-infrared data of Infrared Astronomical Satellite (IRAS) following Casoli et al (1986) and Guzmán et al (2012). We see that the pulsation periods of the unstable models are several 10-100 days, the same order of the observed periods of the maser sources.…”

Section: Period-luminosity Relationmentioning

confidence: 70%

Direct Diagnostics of Forming Massive Stars: Stellar Pulsation and Periodic Variability of Maser Sources

Inayoshi

Sugiyama

Hosokawa

et al. 2013

ApJ

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The 6.7 GHz methanol maser emission, a tracer of forming massive stars, sometimes shows enigmatic periodic flux variations over several 10-100 days. In this Letter, we propose that these periodic variations could be explained by the pulsation of massive protostars growing under rapid mass accretion with rates ofṀ * 10 −3 M yr −1 . Our stellar evolution calculations predict that the massive protostars have very large radii exceeding 100 R at maximum, and here we study the pulsational stability of such bloated protostars by way of the linear stability analysis. We show that the protostar becomes pulsationally unstable with various periods of several 10-100 days depending on different accretion rates. With the fact that the stellar luminosity when the star is pulsationally unstable also depends on the accretion rate, we derive the period-luminosity relation log(L/ L ) = 4.62 + 0.98 log(P /100 days), which is testable with future observations. Our models further show that the radius and mass of the pulsating massive protostar should also depend on the period. It would be possible to infer such protostellar properties and the accretion rate with the observed period. Measuring the maser periods enables a direct diagnosis of the structure of accreting massive protostars, which are deeply embedded in dense gas and are inaccessible with other observations.

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“…The latter correlation could suggest that the jets are ionized by the energetic photons produced in strong shocks rather than photoionized by the stellar radiation (Rodriguez 1989). However, for the few jets observed toward high-mass YSOs, the Lyman continuum calculated from the YSO bolometric luminosity generally exceeds the value inferred from the radio luminosity (Anglada et al 2015;Guzmán et al 2012), suggesting that stellar photoionization could still be the main ionization process. We also note that most previous surveys of radio jets, performed with the Very Large Array (VLA), reached a sensitivity threshold of a few 0.1 mJy.…”

Section: Structure and Nature Of Ionized Winds From Radio Continuum Imentioning

confidence: 96%

Outflow structure within 1000 au of high-mass YSOs

Moscadelli

Sánchez-Monge

Goddi

et al. 2015

A&A

132

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Context. In high-mass (≥7 M ) star formation (SF) studies, high-angular resolution is crucial for resolving individual protostellar outflows (and possibly accretion disks) from the complex contribution of nearby (high-and low-mass) young stellar objects (YSO). Previous interferometric studies have focused mainly on single objects. Aims. A sensitive survey at high angular resolution is required to investigate outflow processes in a statistically significant sample of high-mass YSOs and on spatial scales relevant to testing theories. Methods. We selected a sample of 40 high-mass YSOs from water masers observed within the BeSSeL Survey. We investigated the 3D velocity and spatial structures of the molecular component of massive outflows at milli-arcsecond angular resolution using multi-epoch Very Long Baseline Array (VLBA) observations of 22 GHz water masers. We also characterize the ionized component of the flows using deep images of the radio continuum emission with resolutions of ∼0. 2, at 6, 13, and 22 GHz with the Jansky Very Large Array (JVLA). Results. We report the first results obtained for a subset of 11 objects from the sample. The water maser measurements provide us with a very accurate description of the molecular gas kinematics. This in turn enables us to estimate the momentum rate of individual outflows, varying in the range 10 −3 -10 0 M yr −1 km s −1 , among the highest values reported in the literature. In all the observed objects, the continuum emission at 13 and 22 GHz has a compact structure, with its position coincident with that of the water masers. The 6 GHz continuum consists of either compact components (mostly well aligned with the 13 and/or 22 GHz sources) or extended emission (either highly elongated or approximately spherical), which can be offset by up to a few arcseconds from the water masers. The unresolved continuum emission associated with the water masers likely points to the YSO location. The comparison of the radio continuum morphology to the maser spatial and 3D velocity distribution shows that five out of eleven high-mass YSOs emit a collimated outflow, with a flow semi-opening angle in the range 10• -30• . The remaining six sources present a more complicated relationship between the geometry of the radio continuum and water maser velocity pattern; therefore, no firm conclusions can be drawn regarding their outflow structure. In two sources, the 6 GHz continuum emission shows a highly elongated structure with a negative spectral index down to −1.2. We interpret this finding in terms of synchrotron emission from relativistic electrons accelerated in strong shocks, which indicates that non-thermal continuum emission could be common in high-mass protostellar jets. The Lyman continua derived from bolometric luminosities always exceed those obtained from the radio luminosities. Conclusions. These first results suggest that collimated outflows or jets can be common in high-mass YSOs and, in a couple of cases, provide hints that magnetic fields could be important in driving ...

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Search for Ionized Jets Toward High-Mass Young Stellar Objects

Cited by 55 publications

References 61 publications

ATLASGAL-selected massive clumps in the inner Galaxy

ATLASGAL-selected massive clumps in the inner Galaxy

Direct Diagnostics of Forming Massive Stars: Stellar Pulsation and Periodic Variability of Maser Sources

Outflow structure within 1000 au of high-mass YSOs

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