SPITZERSPECTRAL LINE MAPPING OF PROTOSTELLAR OUTFLOWS. I. BASIC DATA AND OUTFLOW ENERGETICS

Abstract

We report the results of spectroscopic mapping observations carried out toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623 molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations, covering the 5.2 − 37 µm spectral region, provide detailed maps of the 8 lowest pure rotational lines of molecular hydrogen and of the [SI] 25.25 µm and [FeII] 26.0 µm fine structure lines. The molecular hydrogen lines, believed to account for a large fraction of the radiative cooling from warm molecular gas that has been heated by a non-dissociative shock, allow the energetics of the outflows to be elucidated. Within the regions mapped towards these 5 outflow sources, total H 2 luminosities ranging from 0.02 to 0.75 L ⊙ were inferred for the sum of the 8 lowest pure rotational transitions. By contrast, the much weaker [FeII] 26.0 µm fine structure transition traces faster, dissociative shocks; here, only a small fraction of the fast shock luminosity emerges as line radiation that can be detected with Spitzer/IRS. Chen et al. (2008) using both the Australian Telescope Compact Array and Spitzer, reveal masses of 2.12 and 0.05 M ⊙ , hydrogen (H+2H 2 ) densities of 2.6 and 2.2×10 7 cm −3 , and hydrogen column densities of 9.4 and 2.6×10 23 cm −2 , respectively. Fits to the spectral energy distribution of IRS 1 and IRS 2 based on these more recent data imply bolometric luminosities Recent observations of the circumstellar envelope around IRS 1 and IRS 2 by

c2dSpitzerIRS spectra of embedded low-mass young stars: gas-phase emission lines

“…Mapping observations (e.g. Neufeld et al 2009) show that, in general, the H 2 high-J lines have a similar distribution to the Tables 3 and 4 are shown as grayscale images with dashed contours. The upper limits are presented as number density distributions with the contours bracketing the 10 and 90% ranges.…”

Waves on the surface of the Orion molecular cloud

“…Examining the Spitzer infrared spectrograph (IRS) archival spectrum of the second Ripple (Fig. 2c), we find no trace of highly ionised species [FeII]), that would attest to the presence of a high velocity Herbig-Haro shock 13,14,15 (the [SIII] emission detected here is spatially associated to the HII region).…”

“…Examining the Spitzer infrared spectrograph (IRS) archival spectrum of the second Ripple (Fig. 2c), we find no trace of highly ionised species ([NeIII], [FeII]), that would attest to the presence of a high velocity Herbig-Haro shock 13,14,15 (the [SIII] emission detected here is spatially associated to the HII region).The comparison between the spatial distribution of Polycyclic Aromatic Hydrocarbons (PAHs), H2 0-0 S(1) pure rotational line intensity, and 12 CO (2-1) emissions in an East to West cut across the Ripples (marked 2 in Fig. 2b) shows a stratification with PAHs 2 more to the East, followed by H2 and then CO emission (Fig.…”

“…) where a series of 5 surprisingly regular wavelets (the Ripples hereafter) enshrouding an elongated molecular cloud, subject to a strong velocity gradient (7-9 km.s -1 .pc -1 , Fig. 1.c and 2.a), are seen.A possibility would be that the CO structure results from the outflow of a young protostar, and the IR emission from the associated Herbig-Haro objects 13,14,15 . However, we do not find any evidence of an embedded protostar able to drive an outflow in this region, neither in the Spitzer IRAC/MIPS images nor in the SIMBAD database.…”

The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1

“…The L1157 outflow, located at a distance estimated to be between 250 pc (Looney et al 2007) and 440 pc (Viotti 1969) may be regarded as the ideal laboratory for observing the effects of shocks on the gas chemistry, being the archetype of the socalled chemically rich outflows (Bachiller et al 2001). The lowluminosity (4-11 L ) Class 0 protostar IRAS20386+6751 drives a precessing powerful molecular outflow associated with several bow shocks seen in CO (Gueth et al 1996) and in IR H 2 images (Davis & Eislöffel 1995;Neufeld et al 2009). In particular, the brightest blue-shifted bow-shock, called B1 (Fig.…”