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More radio diagnostics
N.B.: the sequence of maser appearance (water > methanol > OH) overlaps - e.g. methanol-only can mean earliest stages of a high-mass star, but could also be in more evolved YSO disc. As ever, multiple diagnostics are needed.
Extended/Early
Cloud collapse starts, ices boil off grains. IR core (can even be
obscured down to mm), ?type II methanol masers in accretion disc
and/or outflow - usually assumed to be around massive stars.
Next, H2O often high velocity, apparently in outflows from v. early
(pre-UCHII, pre-bright-IR) high-mass YSO.
Ultra-compact HII (UCHII) region - ionised region produced by
protostar as it heats up, seen in radio continuum. Type I methanol
masers.
Finally OH usually associated with disc and/or outflow in proximity to
UCHII regions, but occasionally weak ones seen assoc with post-shock
outflows.
CO outflow, usually assoc with massive YSO.
YSOs also have extended radio emission but probably disc wind
especially if massive, i.e. at later stage when central star is
ablating disc.
More evolved YSO
Low-mass stars microjets hot, ionised (proplyds)
Methanol also seen after UCHII region formed, there are reports of H2O
and methanol assoc. with low-mass stars, sometimes possibly in
Kelperian motion around more advanced protostellar stage.
Synchrotron assoc w coronal X-ray
(?? radio can be resolved and so distinguish from wind x-ray???)
Low radio can be due to high density (Raisin-T Coulomb losses - lower
freq goes first, for weakly rel. accell. this is faster than 'normal'
radiative synchrotron losses)
Data etc.
In addition to data already listed for Demo:
NVSS survey already in Vizier - presence of radio emission detected by NVSS suggests UCHII (if not something quite different - check with catalogue). Compact (stellar/coronal) radio probably too faint for NVSS.
Becker et al. 1994 ApJS 91 347 5 GHz Galactic Plane survey
NGC1333 Smith et al. 1999 A&A 349 475 VLA Radio counterparts to X-ray bright YSO.
Non-thermal > stellar origin (as distinct from UCHII)
Could also search for maser/molecular line catalogues.
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