HERSCHELFAR-INFRARED SPECTRAL-MAPPING OF ORION BN/KL OUTFLOWS: SPATIAL DISTRIBUTION OF EXCITED CO, H₂O, OH, O, AND C⁺IN SHOCKED GAS

Abstract

We present ∼2 ×2 spectral-maps of Orion BN/KL outflows taken with Herschel at ∼12 resolution. For the first time in the far-IR domain, we spatially resolve the emission associated with the bright H 2 shocked regions "Peak 1" and "Peak 2" from that of the Hot Core and ambient cloud. We analyze the ∼54-310 µm spectra taken with the PACS and SPIRE spectrometers. More than 100 lines are detected, most of them rotationally excited lines of 12 CO (up to J=48-47), H 2 O, OH, 13 CO, and HCN. Peaks 1/2 are characterized by a very high L(CO)/L F IR ≈5×10 −3 ratio and a plethora of far-IR H 2 O emission lines. The high-J CO and OH lines are a factor ≈2 brighter toward Peak 1 whereas several excited H 2 O lines are 50% brighter toward Peak 2. Most of the CO column density arises from T k ∼200-500 K gas that we associate with low-velocity shocks that fail to sputter grain ice mantles and show a maximum gas-phase H 2 O/CO 10 −2 abundance ratio. In addition, the very excited CO (J>35) and H 2 O lines reveal a hotter gas component (T k ∼2500 K) from faster (v S >25 km s −1 ) shocks that are able to sputter the frozen-out H 2 O and lead to high H 2 O/CO 1 abundance ratios. The H 2 O and OH luminosities cannot be reproduced by shock models that assume high (undepleted) abundances of atomic oxygen in the preshock gas and/or neglect the presence of UV radiation in the postshock gas. Although massive outflows are a common feature in other massive star-forming cores, Orion BN/KL seems more peculiar because of its higher molecular luminosities and strong outflows caused by a recent explosive event. Subject headings: stars: protostars ISM: jets and outflows infrared: ISM shock waves jr.goicoechea@icmm.csic.es * Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

HERSCHEL/HIFI SPECTRAL MAPPING OF C+, CH+, AND CH IN ORION BN/KL: THE PREVAILING ROLE OF ULTRAVIOLET IRRADIATION IN CH+ FORMATION

“…Overall the intensitiy distribution of CH + is very similar to that of C + mapped over the same area by Goicoechea et al (2015aGoicoechea et al ( , 2015b.…”

The ALMA View of the OMC1 Explosion in Orion

“…Far-infrared observations of high rotational states of CO with the Herschel space telescope (Goicoechea et al 2015) show that the spectral line energy distribution (SLED) can be well fit with three components having temperatures of 200, 500, and 2500 K. The ALMA data cube shows that most streamers have brightness temperatures between 20 and 90 K and Doppler widths of ΔV∼5 to 10 km s −1 . Assuming cylindrical geometry, a characteristic width or depth of 1 2 (500 au), and a 12 CO abundance ( ) = -X n 10 H CO 4 2 , the relation between column density of CO and the density of H 2 is ( ) =Ń n 7.5 10 H CO 11 2 cm −2 .…”

CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations∗

“…Orion S and W49N were observed in the standard "chop-nod" mode with a chopper throw of ±6 arcmin. Owing to the very high far-infrared continuum fluxes toward Sgr B2(M) and Orion KL (above the nominal saturation limits of PACS), these sources were observed in a specific non-standard engineering procedure (PacsCalWaveCalNo-ChopBurst; see Goicoechea et al 2015). In order to avoid contamination from the bright Orion and Sgr B2 extended clouds, the "unchopped" observing mode was used.…”

“…For sources with semi-extended emission this means that accurate line fluxes can only be extracted by adding the fluxes measured in apertures that cover several spaxels. OrionKL and SgrB2 data were calibrated and reduced as described in Goicoechea et al (2015). Reductions of OrionS and W49N observations follow a similar method to that described in Gerin et al (2015).…”

“…However, fluxes in OrionKL were determined as described in Goicoechea et al (2015) for a 3×3 spaxel (≈30″×30″) aperture centered on the hot core. This smaller region was used for extracting fluxes instead of the full array since the PACS footprint centered on OrionKL is contaminated by OrionH 2 Peak1, which gives rise to most of the high-J CO emission (see Figure 1 in Goicoechea et al 2015). The line fluxes toward SgrB2(M) and OrionS were extracted from the full 5×5 spaxel aperture.…”