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How to distinguish between jets and HCHIIR?

Andres Guzman F. Universidad de Chile

HCHIIR workshop Sydney, 8 Sept 2010


Ionized jets and HCHIIR
Both are related to very earl y stages of high mass star formation


They share similar characteristics when observed in cm radio continuum


They will be confused in some degree depending on which criteria we used to identify young stellar objects



Ionized jets and HCHIIR
1) First criterion for identifying early stages: Less radio continuum than expected for a optically thin HIIR

Sewilo et al. 2004



IRAS 16547 G345.5


Ionized jets and HCHIIR
Under-luminous in radio because: Physical conditions of the ionized gas: Optically thick HIIR, (young, maybe trapped) Physical conditions of the "prot ostar" Less UV and Teff from young objects (puffed star) Physical process of ionization In jets at least.


Ionized jets and HCHIIR

Guzman et al. 2010

Anglada, 1996


Ionized jets and HCHIIR
2) Second criterion: Density estimation using radio continuum. (Spectral index)
n Uni for m HII reg io


Ionized jets and HCHIIR
3) Third criterion: Radio continuum spectrum. Modeled as spheres or cones with a pow density, both phenomena have transition where the emission is characterized by a index between -0.1 and 2, depending on profile (beta): er-law in regions spectral the density


Ionized jets and HCHIIR
3) Ionized shell with power law index
Inner radius nu-critic Outer


Ionized jets and HCHIIR
3) Ionized shell with power law index For beta<3/2 there is no transition region Most regions are well fitted by density profiles with beta>2 Recombination balance implies that most of theionizing photons are absorbed "nearby" the source.


Integral diverges if Beta>3/2 & R1 0

Given a initial density, beta>3/2 : arbitrarily small HIIR beta<3/2 :R2~RStromgren


Ionized jets and HCHIIR
3) Spectral index of the deconvolved size (radio continuum). This is the first of the criteria that together with the flux spectral index could disentangle between jet and HCHIIR. Geometrical (and kinematical) "lib erty" of the jet. Width goes as r^epsilon (epsilon=1 conical )


Ionized jets and HCHIIR
4) Presence of radio lobes: Emission from the shocked-ionized gas (not the jet itself) These have been the confirmation of the jet phenomena. They also allow us also to estimate jet dynamics


Ionized jets and HCHIIR
5) Circumstantial evidence for jets: Molecular outflows Shock excited gas emission (e.g. G.F., SiO, H2)


Ionized jets and HCHIIR
6) Velocity broadening of hydrogen RRLs Until now, the velocity width of hydrogen RRLs of regions classified as HC rarely goes above 100 km/s. Estimations of massive-protostars-jet-velocities (Ceph A, HH80-81, IRAS16547, G345.5) all range between 300-1000 km/s RRLs peak ~ 1 to 5% of the continuum


Ionized jets and HCHIIR
7) Consistent with FIR peak? We have an example of a faint but dense region consistent with 24um peak (MIPS)

UCHIIR CHIIR


Ionized jets and HCHIIR
Final remarks and conclusions
All these criteria and analysis should be useful in order to present a consistent physical context. Until now, HCHIIR have less "requirements" other than density or EM



Ionized jets and HCHIIR

EM10^7 G337 3.811 I13134A 0.197 I13134B 0.789 I13134C 19.5 17238 11.2 G345.01 18.9 G317 21.13 G333.13 10.78

diampc 0.0266 0.032 0.0064 0.0011 0.0197 0.0128 0.025 0.074

dens10^4 3.7866 0.7845 3.5204 41.5 7.51 12.15 9.15 3.8

comment normal-dense normal normal-dense dense dense dense dense normal-dense