HH s at NIR Observations Diagnosis. OMC 1 Outflow t = 500 yr). Orión Nebula. NKL. Trapezium. (L = 10 5 L o t << 10 5 yr). (L = 10 5 L o t < 10 5 yr ). OMC1-S. (L = 10 4 L o , t < 10 5 yr). Infrared. “ continuum. “line”. H 2. 1-0 S(1).
t = 500 yr)
(L = 105 Lo
t << 105 yr)
(L = 105 Lo
t < 105 yr)
(L = 104 Lo ,
t < 105 yr)
The spectrum of the infrared nebula Beckling-Neugebauer (BN) of Orión:
From the analysis of H2 molecular gas at T~2000K
Lines of H2 2.12mm show FWHM 20-60 kms-1 vg~40 kms-1 (and up to 100 kms-1)----->PROBLEM: Models found that shocks with v>25kms-1 disociate the H2 molecule (Kwan 1977 ApJ, 216, 713)
The first observations (low-resolution spectroscopy) showed that the low-excitation HHs had strong H2 emission
The strongest H2 emission line is at 2.12mm
Usually, the intesities of the Ha and H2 at2.12mm emission lines have similar strengths.
Emission lines of H2 cooling of the shock in HHs H2 emission clues on the physic in the low-velocity regime; “complementary” information from the one obtained from atomic line emission at optical wavelengths.
Because its characteristic cooling time is shorter H2 emission lines trace the regions where the jet/ambient interaction is more recent than the regions traced by optical lines ( younger jets).
Also, we can trace the jet closer to the exciting source (as in Ha)
HH emission lines at NIR:
[FeII] (~1.64 mm) (H)
H2 (~2.12 mm) (K)
In few cases, the NIR “nebulosities” are the counterparts of HH wellkown jets. However the optical and nir emissions are not fully coincident (there is someshift).
Other NIR jets have not optical counterpart:
The optical counterpart of a NIR jet is detected far from the source
than the NIR jet.
Optical and NIR emissions are tracing different physical conditions
In general, is not possible to predict the NIR emission from the optical one.
Tedds et al.
RmxAA 13,103 (2002)
ApJ, 550, L87 (2001)
*There is a complex relationship between the spatial
distribution of both emissions.
*At the bow-shocks:
+ [FeII] : brighter at the apex : (vs)n
has its maximum
+H2: brighter at the winds (vs)n lower.
MNRAS, 318, 747
Source: Class I, in a phase of high accretion; binary system
d~450pc; located at the border of a Bok globule.
Atomic and molecular flows associated.
The presence of Brg emission near the source is signature of high excitation
conditions in the region.
Kinematics: velocities of the ionized ([FeII] and neutral (H2) emissions
(Velocity, in LSR and corrected
For a parental cloud velocity
Radial velocitues computed by a Gaussian-fit to the line profile of each knot
Blue and redshifted values, decreasing as the distance to the source increases
Two velocity components in some knots.
Using the H2 detected transitions excitation diagrams:
If collisional de-excitation is assumed to dominate, H2 population levelswill be in LTE Boltzmann distribution:
Ni/Nj = gi/gj exp [-(Ei – Ej)/kTex] N: column density ~ F line
Plot ln[N(n,J)/gn,J] vs E(n,J) linear fit slope ~ T-1
gn,J : statistical weight of a given (gn,J) ro-vibrational level
E(n,J): Excitation energy
Gredel, A&A,292,580 (1994)
The measured intensity, I(v,J) , of a given H2 line is used to calculate the column density, N(v,J), of the upper excitation level of the transition. For optically thin emission,
Plot of ln(N(v,J) vs excitation energy E(v,J):
Continuum: fit for T = 2200 K
Dashed: Fit using the four lowest levels, T = 1900K
Giannini et al., 2008, A&A,481,123
[FeII] shows a rich line spectrum
in the J-K wavelength range
(1.1-2.5 mm), very useful for the
analysis of the ionized component in
shocks produced in regions with high
nc [Fe] >> nc [SII], [OII]
Use to derive ne in regions of ne > 104 cm-3 and/or with higher extinction.
*As a tracer of T:
Lines in the range 1.1-2.5 mm arise from a level with four sublevels ~
DE line ratios are weakly dependent on T
a good choice is to combine lines from another range ex: 8671 A + 1.64 mm
of HH 1
(see Nisini et al. ,2005, A&A ,441, 159 for details).