<i>SPITZER</i>AND HEINRICH HERTZ TELESCOPE OBSERVATIONS OF STARLESS CORES: MASSES AND ENVIRONMENTS

Stutz, Amelia M.; Rieke, G. H.; Bieging, John H.; Balog, Z.; Heitsch, Fabian; Kang, Miju; Peters, William L.; Shirley, Yancy L.; Werner, M. W.

doi:10.1088/0004-637x/707/1/137

Cited by 44 publications

(62 citation statements)

References 88 publications

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“…The morphology of L1570 in the two-dimensional map of the cloud in 13 CO made by Arquilla & Goldsmith (1985) looks very much similar to the one shown in the Fig. 20 (also see the 8 μm shadow image of L1570 produced by Spitzer telescope; Stutz et al 2009). The velocity structure of L1570 by Arquilla & Goldsmith (1986) gives a complex picture of the region.…”

Section: Magnetic Field Geometrysupporting

confidence: 67%

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

Eswaraiah

Maheswar

Pandey

et al. 2013

A&A

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Aims. We aim to map the magnetic field geometry and to study the dust properties of the starless cloud, L1570, using multi-wavelength optical polarimetry and photometry of the stars projected on the cloud. Methods. The direction of the magnetic field component parallel to the plane of the sky of a cloud can be obtained using polarimetry of the stars projected on and located behind the cloud. It is believed that the unpolarized light from the stars background to the cloud undergoes selective extinction while passing through non-spherical dust grains that are aligned with their minor axes parallel to the cloud magnetic field. The emerging light becomes partially plane polarized. The observed polarization vectors trace the direction of the projected magnetic field of the cloud. We made R-band imaging polarimetry of the stars projected on a cloud, L1570, to trace the magnetic field orientation. We also made multi-wavelength polarimetric and photometric observations to constrain the properties of dust in L1570. Results. We estimated a distance of 394 ± 70 pc to the cloud using 2MASS JHK s colors. Using the values of the Serkowski parameters, σ 1 , , λ max , and the position of the stars on the near-infrared color-color diagram, we identified 13 stars that could possibly have intrinsic polarization and/or rotation in their polarization angles. One star, 2MASS J06075075+1934177, which is a B4Ve spectral type, shows diffuse interstellar bands in the spectrum in addition to the Hα line in emission. There is an indication for slightly bigger dust grains toward L1570 on the basis of the dust grain size-indicators such as λ max and R V values. The magnetic field lines are found to be parallel to the cloud structures seen in the 250 μm images (also in the 8 μm and 12 μm shadow images) of L1570. Based on the magnetic field geometry, the cloud structure, and the complex velocity structure, we conclude that L1570 is in the process of formation due to the converging flow material mediated by the magnetic field lines. A structure function analysis showed that in the L1570 cloud region the large-scale magnetic fields are stronger than the turbulent component of the magnetic fields. The estimated magnetic field strengths suggest that the L1570 cloud region is subcritical and hence could be strongly supported by the magnetic field lines.

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Section: Magnetic Field Geometrysupporting

confidence: 67%

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

Eswaraiah

Maheswar

Pandey

et al. 2013

A&A

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“…Since coreshine is interstellar radiation scattered by dust grains larger than the majority of grains in the ISM, it could indicate that grain growth is or has been inefficient in B68. Only about half of the cores investigated so far show the effect (Stutz et al 2009;Pagani et al 2010).…”

Section: From Absorption To Emissionmentioning

confidence: 99%

The Earliest Phases of Star formation (EPoS) observed withHerschel: the dust temperature and density distributions of B68

Nielbock

Launhardt

Steinacker

et al. 2012

A&A

129

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Context. Isolated starless cores within molecular clouds can be used as a testbed to investigate the conditions prior to the onset of fragmentation and gravitational proto-stellar collapse. Aims. We aim to determine the distribution of the dust temperature and the density of the starless core B68. Methods. In the framework of the Herschel guaranteed-time key programme "The Earliest Phases of Star formation" (EPoS), we have imaged B68 between 100 and 500 μm. Ancillary data at (sub)millimetre wavelengths, spectral line maps of the 12 CO (2-1), and 13 CO (2-1) transitions, as well as an NIR extinction map were added to the analysis. We employed a ray-tracing algorithm to derive the 2D mid-plane dust temperature and volume density distribution without suffering from the line-of-sight averaging effects of simple SED fitting procedures. Additional 3D radiative transfer calculations were employed to investigate the connection between the external irradiation and the peculiar crescent-shaped morphology found in the FIR maps. Results. For the first time, we spatially resolve the dust temperature and density distribution of B68, convolved to a beam size of 36. 4. We find a temperature gradient dropping from (16.7 ) × 10 5 cm −3 . B68 has a mass of 3.1 M of material with A K > 0.2 mag for an assumed distance of 150 pc. We detect a compact source in the southeastern trunk, which is also seen in extinction and CO. At 100 and 160 μm, we observe a crescent of enhanced emission to the south. Conclusions. The dust temperature profile of B68 agrees well with previous estimates. We find the radial density distribution from the edge of the inner plateau outward to be n H ∝ r −3.5 . Such a steep profile can arise from either or both of the following: external irradiation with a significant UV contribution or the fragmentation of filamentary structures. Our 3D radiative transfer model of an externally irradiated core by an anisotropic ISRF reproduces the crescent morphology seen at 100 and 160 μm. Our CO observations show that B68 is part of a chain of globules in both space and velocity, which may indicate that it was once part of a filament that dispersed. We also resolve a new compact source in the southeastern trunk and find that it is slightly shifted in centroid velocity from B68, lending qualitative support to core collision scenarios.

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“…A&A 563, A106 (2014) Although the central core of LDN183 is surrounded by slightly more mass than most low-mass cores, its general conditions were not substantially different from that of many other low-mass cores. Therefore, it was not entirely surprising that an investigation of other cores in the IRAC bands led to the finding that about half of the selected cores showed scattered light ) (see also Stutz et al 2009, for a small subsample of cores with 3.6 μm excess).…”

Section: Introductionmentioning

confidence: 99%

Detecting scattered light from low-mass molecular cores at 3.6μm

Steinacker

Andersen

Thi

et al. 2014

A&A

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Context. Recently discovered scattered light at 3−5 μm from low-mass cores (so-called "coreshine") reveals the presence of grains around 1 μm, which is larger than the grains found in the low-density interstellar medium. But only about half of the 100+ cores investigated so far show the effect. This prompts further studies on the origin of this detection rate. Aims. We aim to supply criteria for detecting scattered light at 3.6 μm from molecular cloud cores. Methods. From the 3D continuum radiative transfer equation, we derive the expected scattered light intensity from a core placed in an arbitrary direction seen from Earth. We use the approximation of single scattering, consider extinction up to 2nd-order Taylor approximation, and neglect spatial gradients in the dust size distribution. We analyze how scattered light can outshine the absorbing effect of extinction in front of background radiation by the core for given grain properties, anisotropic interstellar radiation field and background field. The impact of the directional characteristics of the scattering on the detection of scattered light from cores is calculated for a given grain size distribution, and local effects like additional radiation field components are discussed. The surface brightness profiles of a core with a 1D density profile are calculated for various Galactic locations, and the results are compared to the approximate detection limits. Results. We find that for optically thin radiation and a constant size distribution, a simple limit for detecting scattered light from a low-mass core can be derived that holds for grains with sizes smaller than 0.5 μm. The extinction by the core prohibits detection in bright parts of the Galactic plane, especially near the Galactic center. For scattered light received from low-mass cores with grain sizes beyond 0.5 μm, the directional characteristics of the scattering favors the detection of scattered light above and below the Galactic center, and to some extent near the Galactic anti-center. We identify the local incident radiation field as the major unknown causing deviations from this simple scheme. Conclusions. The detection of coreshine at a wavelength of 3.6 μm is a complex interplay of the incident radiation, the extinction of the background radiation, the grain properties, and the core properties like sky position and mass.

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SPITZERAND HEINRICH HERTZ TELESCOPE OBSERVATIONS OF STARLESS CORES: MASSES AND ENVIRONMENTS

Cited by 44 publications

References 88 publications

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

A study of the starless dark cloud LDN 1570: Distance, dust properties, and magnetic field geometry

The Earliest Phases of Star formation (EPoS) observed withHerschel: the dust temperature and density distributions of B68

Detecting scattered light from low-mass molecular cores at 3.6μm

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