Transcript Evolution of high-mass YSOs: Pathfinder Sample

Evolution of high-mass YSOs:
Pathfinder Sample
Riccardo Cesaroni, Maite Beltràn, Roberta Paladini
Main steps:
1. Choose templates of high-mass YSOs in
different evolutionary phases
2. Establish characteristics of each phase
3. Select sources in each phase from HiGal survey
4. Optimize characterization using HiGal info
Adopt “classical” evolutionary sequence
(maybe questionable/incomplete, but reasonable starting
point to be improved later)
IR-dark cloud
Work in progress:
HMC (+ HC HII)
1. Identify ~10 templates per
phase
UC HII
2. Obtain images and SEDs
from NIR to (sub)mm
extended HII
3. Establish possible
differences among phases
Choice of templates
• IRDCs relatively easy (Chambers et al. 2009, Beltràn et al.
2006, Pillai et al. 2006,2007): compact submm cores without
GLIMPSE source  then check no MIPSGAL source and no
maser
• HMCs & UCHIIs more difficult: only few HMCs known (e.g.
Kurtz et al. 2000)
many UCHIIs (e.g. Wood & Churchwell 1989, Kurtz et al.
1994), but… many problems
• Extended HIIs easy (lots of optical/radio and recombination
lines catalogs: Sharpless 1959, Rodgers 1960, Paladini et al.
2003, Caswell & Haynes 1980, etc.): optical counterpart, size
> 1 arcminute, electron density ne ~ 10 - 102 cm-3
Problems with HMCs & UCHIIs:
• Contamination: many UCHIIs w/o HMCs but almost
no HMC w/o UCHII  reject HMCs with embedded
“large” UCHIIs
• Authenticity: some UCHIIs might be peaks (w/o star!)
of (resolved out) extended emission  Kurtz et al.
(1999), Kim & Koo (2001) show that only very few
UCHII suffer by this problem
• Extended emission: might affect UCHII properties 
UCHII should dominate within 20”
• Multiplicity: confusion due to >1 UCHIIs inside
HPBW (~20”)  reject complex UCHIIs and clusters
of UCHIIs; accept only “simple” morphologies
• Distance: implications on multiplicity, morphology,
etc…  choose more or less same distance (< 9 kpc,
but with some exception)
Additional selection criterion for HiGal: |l|<60° & |b|<1°
For tables of selected sources see HiGal WIKI page
Examples of IRDCs
Examples of HMCs
NOTE: all images and SEDs obtained after smoothing
to 20” resolution (MSX, MIPSGAL 70µm)
Examples of UCHIIs
NOTE: all images and SEDs obtained after smoothing
to 20” resolution (MSX, MIPSGAL 70µm)
Comparison between SEDs of all HMCs and UCHIIs
HMCs
UCHIIs
Findings for HMCs & UCHIIs
• Large majority saturated in MIPSGAL (some also in GLIMPSE
8 µm)
• IRAS fluxes likely overestimate by ~10
• SEDs and morphologies are basically the same for HMCs and
UCHIIs:
– SED = cold mm component + hot IR component
– Morphology = IR peak coincident with submm core
 both HMCs and UCHIIs analogous to IR-P sources of
Molinari et al. (2008)
 perhaps different luminosities i.e. 100 µm fluxes? Only
HiGal will tell us
 need for intermediate phase (MM-P sources) between IRDCs
and HMCs ?
Examples of EHIIs
M16 : 16.95 + 0.79
40 - 250m
(McBreen, Fazio, Jaffe 1982)
GUM 38d: 309.28 - 00.40
( Karr, Manoj, Ohashi 2009 )
H
IRAC 8m
1420 MHz
MIPS 24m
RCW 79: 308.6+0.6
(Zavagno et al. 2006)
H
Red: IRAC 8m
Blue: H
IRAC 8m