Extremely Broad Radio Recombination Maser Lines Toward the High-Velocity Ionized Jet in Cepheus a Hw2

Jiménez-Serra, Izaskun; Martı́n-Pintado, J.; Báez-Rubio, A.; Patel, Nimesh; Thum, C.

doi:10.1088/2041-8205/732/2/l27

Cited by 34 publications

(28 citation statements)

References 29 publications

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“…∼ 270 km/s in low-mass stars to ∼ 1000 km/s in high-mass stars . The average velocity of optical jets is ∼ 750 km/s (Mundt & Ray 1994), a value comparable to Jiménez-Serra et al (2011) and Martí et al (1998) estimates of ∼ 500 km/s in Cepheus A HW2 and HH 80-81 respectively. Whereas the average velocity in optical jets is ∼ 750 km/s, a value of v t = 500 km/s, estimated via proper motion of a radio jet (Martí et al 1998) was adopted as a reasonable approximation of the sample's jets' terminal velocity, in calculating the mass loss rate.…”

Section: Mass Loss Ratesupporting

confidence: 68%

A search for non-thermal radio emission from jets of massive young stellar objects

Obonyo

Lumsden

Hoare

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Massive young stellar objects (MYSOs) have recently been shown to drive jets whose particles can interact with either the magnetic fields of the jet or ambient medium to emit non-thermal radiation. We report a search for non-thermal radio emission from a sample of 15 MYSOs to establish the prevalence of the emission in the objects. We used their spectra across the L-, C-and Q-bands along with spectral index maps to characterise their emission. We find that about 50% of the sources show evidence for non-thermal emission with 40% showing clear non-thermal lobes, especially sources of higher bolometric luminosity. The common or IRAS names of the sources that manifest non-thermal lobes are; V645Cyg, IRAS 22134+5834, NGC 7538 IRS 9, IRAS 23262+640, AFGL 402d and AFGL 490. All the central cores of the sources are thermal with corresponding mass-loss rates that lie in the range ∼ 3 × 10 −7 to 7 × 10 −6 M yr −1 . Given the presence of non-thermal lobes in some of the sources and the evidence of non-thermal emission from some spectral index maps, it seems that magnetic fields play a significant role in the jets of massive protostars. Also noted is that some of the sources show evidence of binarity and variability.

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Section: Mass Loss Ratesupporting

confidence: 68%

A search for non-thermal radio emission from jets of massive young stellar objects

Obonyo

Lumsden

Hoare

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Extremely broad millimeter recombination lines of a possible maser nature have been reported from the high-velocity ionized jet Cep A HW2 (Jiménez-Serra et al 2011). In this case, the difference between the LTE and non-LTE models is less than a factor of two and in some of the transitions it is necessary to multiply the non-LTE model intensities by a factor of several to agree with the observations.…”

Section: Non-lte Radio Recombination Linesmentioning

confidence: 89%

Radio jets from young stellar objects

Anglada

Rodrı́guez²,

Carrasco-González³

2018

Astron Astrophys Rev

137

151

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Jets and outflows are ubiquitous in the process of formation of stars since outflow is intimately associated with accretion. Free-free (thermal) radio continuum emission in the centimeter domain is associated with these jets. The emission is relatively weak and compact, and sensitive radio interferometers of high angular resolution are required to detect and study it. One of the key problems in the study of outflows is to determine how they are accelerated and collimated. Observations in the cm range are most useful to trace the base of the ionized jets, close to the young central object and the inner parts of its accretion disk, where optical or near-IR imaging is made difficult by the high extinction present. Radio recombination lines in jets (in combination with proper motions) should provide their 3D kinematics at very small scale (near their origin). Future instruments such as the Square Kilometre Array (SKA) and the Next Generation Very Large Array (ngVLA) will be crucial to perform this kind of sensitive observations. Thermal jets are associated with both high and low mass protostars and possibly even with objects in the substellar domain. The ionizing mechanism of these radio jets appears to be related to shocks in the associated outflows, as suggested by the observed correlation between the centimeter luminosity and the outflow momentum rate. From this correlation and that of the centimeter luminosity with the bolometric luminosity of the system it will be possible to discriminate between unresolved HII regions and jets, and to infer additional physical properties of the embedded objects. Some jets associated with young stellar objects (YSOs) show indications of nonthermal emission (negative spectral indices) in part of their lobes. Linearly polarized synchrotron emission has been found in the jet of HH 80-81, allowing one to measure the direction and intensity of the jet magnetic field, a key ingredient to determine the collimation and ejection mechanisms. As only a fraction of the emission is polarized, very sensitive observations such as those that will be feasible with the interferometers previously mentioned are required to perform studies in a large sample of sources. Jets are present in many kinds of astrophysical scenarios. Characterizing radio jets in YSOs, where thermal emission allows one to determine their physical conditions in a reliable way, would also be useful in understanding acceleration and collimation mechanisms in all kinds of astrophysical jets, such as those associated with stellar and supermassive black holes and planetary nebulae.

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“…A possible drawback of (sub)mm RLs is that the free-free continuum may be contaminated by dust emission. Another problem is that they are out of LTE more easily than cm lines, so their interpretation may require careful modeling (e.g., Jiménez-Serra et al 2011;Peters et al 2012). As shown below, our simple LTE interpretation seems to be reasonable, but it is possible that a significant fraction of the 1.3-mm continuum comes from dust in the line of sight.…”

Section: Appendix A: Linewidth Of Recombination Linesmentioning

confidence: 89%

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

Galván-Madrid

Goddi

Rodrı́guez

2012

A&A

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Compared to their centimeter-wavelength counterparts, millimeter recombination lines (RLs) are intrinsically brighter and are free of pressure broadening. We report observations of RLs (H30α at 231.9 GHz, H53α at 42.9 GHz) and the millimeter and centimeter continuum toward the Becklin-Neugebauer (BN) object in Orion, obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) science verification archive and the Very Large Array (VLA). The RL emission appears to be arising from the slowly-moving, dense (N e = 8.4 × 10 6 cm −3 ) base of the ionized envelope around BN. This ionized gas has a relatively low electron temperature (T e < 4900 K) and small ( 10 km s −1 ) bulk motions. Comparing our continuum measurements with previous (non)detections, it is possible that BN has large flux variations in the millimeter. However, dedicated observations with a uniform setup are needed to confirm this. From the H30α line, the central line-of-sight LSR velocity of BN is 26.3 km s −1 .

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Extremely Broad Radio Recombination Maser Lines Toward the High-Velocity Ionized Jet in Cepheus a Hw2

Cited by 34 publications

References 29 publications

A search for non-thermal radio emission from jets of massive young stellar objects

A search for non-thermal radio emission from jets of massive young stellar objects

Radio jets from young stellar objects

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

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