A 0.8 mm heterodyne facility receiver for the APEX telescope

Schüller

et al. 2014

A&A

Aims. We present an analysis of the dust continuum emission at 870 μm in order to investigate the mass distribution of clumps within infrared dark clouds (IRDCs). Methods. We map six IRDCs with the Large APEX BOlometer CAmera (LABOCA) at APEX, reaching an rms noise level of σ rms = 28 -44 mJy beam −1 . The dust continuum emission coming from these IRDCs was decomposed by using two automated algorithms, Gaussclumps and Clumpfind. Moreover, we carried out single-pointing observations of the N 2 H + (3-2) line toward selected positions to obtain kinematic information. Results. The mapped IRDCs are located in the range of kinematic distances of 2.7-3.2 kpc. We identify 510 and 352 sources with Gaussclumps and Clumpfind, respectively, and estimate masses and other physical properties assuming a uniform dust temperature. The mass ranges are 6-2692 M (Gaussclumps) and 7-4254 M (Clumpfind), and the ranges in effective radius are ∼0.10-0.74 pc (Gaussclumps) and 0.16-0.99 pc (Clumpfind). The mass distribution, independent of the decomposition method used, is fitted by a power law, dN/dM ∝ M α , with an index (α) of −1.60 ± 0.06, consistent with the CO mass distribution and other high-mass star-forming regions.

Section: Molecular Line Datamentioning

confidence: 99%

The mass distribution of clumps within infrared dark clouds. A Large APEX Bolometer Camera study

Gómez

Schüller

et al. 2014

A&A

“…Large-scale maps of the 13 CO and C 18 O J = 3−2 lines were obtained in the on-the-fly (OTF) observations with the APEX-2a facility receiver (Risacher et al 2006). This double sideband (DSB) heterodyne receiver provided receiver DSB temperatures of 60 K and typical system noise from 100 to 200 K. Maps of size ∼300 ×350 were centered on the Orion BN source (α, δ J2000 = 05 h 35 m 14. s 16, −05 • 22 21.…”

Section: Observationsmentioning

confidence: 99%

The APEX-CHAMP⁺view of the Orion Molecular Cloud 1 core

Peng

Zapata

et al. 2012

A&A

Aims.A high density portion of the Orion Molecular Cloud 1 (OMC-1) contains the prominent, warm Kleinmann-Low (KL) nebula plus a farther region in which intermediate to high mass stars are forming. Its outside is affected by ultraviolet radiation from the neighboring Orion Nebula Cluster and forms the archetypical photon-dominated region (PDR) with the prominent bar feature. Its nearness makes the OMC-1 core region a touchstone for research on the dense molecular interstellar medium and PDRs. Methods. Using the Atacama Pathfinder Experiment telescope (APEX), we have imaged the line emission from the multiple transitions of several carbon monoxide (CO) isotopologues over the OMC-1 core region. Our observations employed the 2 × 7 pixel submillimeter CHAMP + array to produce maps (∼300 × 350 ) of 12 CO, 13 CO, and C 18 O from mid-J transitions (J = 6−5 to 8−7). We also obtained the 13 CO and C 18 O J = 3−2 images toward this region. Results. The 12 CO line emission shows a well-defined structure which is shaped and excited by a variety of phenomena, including the energetic photons from hot, massive stars in the nearby Orion Nebula's central Trapezium cluster, active high-and intermediate-mass star formation, and a past energetic event that excites the KL nebula. Radiative transfer modeling of the various isotopologic CO lines implies typical H 2 densities in the OMC-1 core region of ∼10 4 −10 6 cm −3 and generally elevated temperatures (∼50−250 K). We estimate a warm gas mass in the OMC-1 core region of 86−285 M .

“…We used the double sideband receiver APEX-2A equipped with two fast Fourier transform spectrometer (FFTS) backends (Risacher et al 2006;Klein et al 2006). The signal and image sidebands are separated by 12 GHz.…”

Section: Apex Observationsmentioning

confidence: 99%

Initial phases of massive star formation in high infrared extinction clouds

Rygl

Schüller

et al. 2012

A&A

Context. The onset of massive star formation is not well understood because of observational and theoretical difficulties. To find the dense and cold clumps where massive star formation can take place, we compiled a sample of high infrared extinction clouds. We observed the clumps in these high extinction clouds in the 1.2 mm continuum emission and ammonia with the goals of deriving the masses, densities, temperatures, and kinematic distances. Aims. We try to understand the star-formation stages of the high extinction clumps by studying their infall and outflow properties, the presence of a young stellar object (YSO), and the level of the CO depletion. Are the physical parameters, density, mass, temperature, and column density correlated with the star-forming properties? Does the cloud morphology, quantified through the column density contrast between the clump and the clouds, have an impact on the evolution of star formation occurring inside it? Methods. Star-formation properties, such as infall, outflow, CO depletion, and the presence of YSOs, were derived from a molecular line survey performed with the IRAM 30 m and the APEX 12 m telescopes. Results. We find that the HCO + (1-0) transition is the most sensitive for detecting infalling motions. SiO, an outflow tracer, was mostly detected toward sources with infall, indicating that infall is accompanied by collimated outflows. We calculated infall velocities from the line profiles and found them to be of the order of 0.3-7 km s −1 . The presence of YSOs within a clump depends mostly on the clump column density; no indication of YSOs were found below 4 × 10 22 cm −2 . Conclusions. Star formation is on the verge of beginning in clouds that have a low column density contrast; the infall is not yet present in the majority of the clumps. The first signs of ongoing star formation are broadly observed in clouds where the column density contrast between the clump and the cloud is higher than two; most clumps show infall and outflow. Finally, we find the most evolved clumps in clouds that have a column density contrast higher than three; in many clumps, the infall has already halted, and toward most clumps we found indications of YSOs. Hence, the cloud morphology, based on the column density contrast between the cloud and the clumps, seems to have a direct connection with the evolutionary stage of the objects forming inside.