A New Look at Stellar Outflows: Spitzer Observations of the HH 46/47 System

Abstract

We present the Early Release Observations of the HH 46/47 system and HH 46 IRS 1 source, taken with the three instruments aboard the Spitzer Space Telescope. The optically invisible southwest lobe, driven by the HH 47C bow shock, is revealed in full detail by the Infrared Array Camera (IRAC) images and displays a ''loop''-like morphology. Both of the mid-infrared outflow lobes are narrower than those of CO flow. We believe that the combination of emission by H 2 rotational lines [S(11)-S(4)] and some atomic lines, which fall within the IRAC passbands, are responsible for the bulk of the observed emission, although contributions from the 3.3, 6.2, and 7.7 m polycyclic aromatic hydrocarbon emission bands cannot be ruled out. Weak spectral features corresponding to these emitters are present in the Infrared Spectrograph spectrum of the HH 47A bow shock. The spectrum of HH 46 IRS 1 shows remarkable similarities to those of high-mass protostars, which include the presence of H 2 O, CO 2 , CH 4 , and possibly NH 3 , CH 3 OH, and NH þ 4 ices. The high ice abundances and the lack of signs of thermal processing indicate that these ices in the envelope are well shielded from the powerful outflow and its cavity. Emission from the Bok globule at 24 m is detected and displays a similar structure to that observed at 8 m.

APEX-CHAMP+high-JCO observations of low-mass young stellar objects

“…In the map of 13 CO 6-5, lines are only detected at the central position and at neighbouring pixels along the outflow. Figure 5 shows the total distribution of 12 CO 6-5 over the entire area, overplotted over the Spitzer image of Noriega-Crespo et al (2004) with the Spitzer-IRAC 1, 2 and 4 bands (3.6, 4.5 and 8.0 μm respectively). The CO 6-5 integrated intensities follow the outflow but do not extend all the way out to the bow shock.…”

“…The bow shock associated with the red outflow lobe is clearly visible in the IR images of Noriega-Crespo et al (2004), located at a relative offset of (−100 , −60 ) with respect to the source. Additional observations of this bow shock in CO 6-5, [C I] 2-1 and 13 CO 6-5 were carried out over a 90 by 60 area.…”

“…The temperature at the inner boundary was taken to be 250 K. For the SED, fluxes were used at 60 and 100 μm (IRAS, Henning et al 1993), 850 μm (SCUBA archive, Di Francesco et al 2008), 870 μm (LABOCA, this work) and 1.3 mm ( SEST Henning et al 1993). No emission from MIPS at 24 μm or ISO-SWS (Nisini et al 2002;Noriega-Crespo et al 2004) was used. The 24 μm flux is included in the figure as reference.…”

“…The Young Stellar Object (YSO) HH 46 IRS 1 (RA = 08 h 25 m 43.9 s , Dec = −51 d 00 h 36 s (J2000) ), located at the edge of an isolated Bok Globule (D = 450 pc) in the southern hemisphere (Schwartz 1977), is well-known for its spectacular outflow (Reipurth & Heathcote 1991), observed at both visible and infrared (IR) wavelengths with the Hubble and Spitzer Space Telescopes (e.g., Heathcote et al 1996;Stanke et al 1999;Noriega-Crespo et al 2004;Velusamy et al 2007). Deep Hα observations using the VLT have revealed bow shocks associated with the HH 46 outflow up to a parsec away from the central source (Stanke et al 1999).…”

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

“…Take as an example the isolated source HH 46 IRS (IRAS08242-5050) imaged with the Spitzer Space Telescope (see Noriega-Crespo et al 2004;Velusamy et al 2007, and references cited) and studied in detail with submillimeter molecular lines as well as dust continuum emission (see summary in van Kempen et al 2009b). The young star is surrounded by a roughly spherically symmetric envelope with a mass of ∼5 M and a power-law density structure, with n(H 2 ) ≈ 10 6 cm −3 at 1000 AU from the star, decreasing to ∼10 5 cm −3 at ∼7000 AU.…”