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The complete far-infrared and submillimeter spectrum of the Class 0 protostar Serpens SMM1 obtained with Herschel. Characterizing UV-irradiated shocks heating and chemistry | | Javier R. Goicoechea
; J. Cernicharo
; A. Karska
; G.J. Herczeg
; E.T. Polehampton
; S. F. Wampfler
; L. E. Kristensen
; E.F. van Dishoeck
; M. Etxaluze
; O. Berne
; R. Visser
; | | Date: |
18 Sep 2012 | | Abstract: | We present the first complete 55-671 um spectral scan of a low-mass Class 0
protostar (Serpens SMM1) taken with the PACS and SPIRE spectrometers on board
Herschel. More than 145 lines have been detected, most of them rotationally
excited lines of 12CO (full ladder from J=4-3 to 42-41), H2O, OH, 13CO, HCN and
HCO+ . Bright [OI]63,145um and weaker [CII]158 and [CI]370,609um lines are also
detected. Mid-IR spectra retrieved from the Spitzer archive are also first
discussed here, they show clear detections of [NeII], [FeII], [SiII] and [SI]
fine structure lines as well as weaker H2 S(1) and S(2) pure rotational lines.
The observed line luminosity is dominated by CO (~54%), H2O (~22%), [OI] (~12%)
and OH (~9%) emission. A non-LTE model allowed us to quantify the contribution
of the 3 different temperature components suggested by the 12CO rotational
ladder (Tk(hot)~800 K, Tk(warm)~375 K and Tk(cool)~150 K). Gas densities
n(H2)~5x10^6 cm^-3 are needed to reproduce the observed far-IR lines arising
from shocks in the inner protostellar envelope for which we derive upper limit
abundances of x(CO)~10^-4, x(H2O)~0.2x10^-5 and x(OH)~10^-6. The lower energy
submm 12CO and H2O lines show more extended emission that we associate with the
cool entrained outflow gas. Fast dissociative J-shocks (v_s > 60 km s^-1) as
well as lower velocity non-dissociative shocks (v_s < 20 km s^-1) are needed to
explain both the atomic lines and the hot CO and H2O lines respectively.
Observations also show the signature of UV radiation and thus, most observed
species likely arise in UV-irradiated shocks. Dissociative J-shocks produced by
an atomic jet are the most probable origin of [OI] and OH emission and of a
significant fraction of the warm CO emission. In addition, H2O
photodissociation in UV-irradiated non-dissociative shocks can also contribute
to the [OI] and OH emission. | | Source: | arXiv, 1209.3966 | | Services: | Forum | Review | PDF | Favorites | |
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