Smoke in the Pipe Nebula: dust emission and grain growth in the starless core FeSt 1-457

Author(s)

Jan Forbrich, Charles J. Lada, Marco Lombardi, Carlos Román-Zúñiga, João Alves

Abstract

Context. The availability of submillimeter dust emission data in an

unprecedented number of bands provides us with new opportunities to

investigate the properties of interstellar dust in nearby clouds.

Aims: The nearby Pipe Nebula is an ideal laboratory to study starless

cores. We here aim to characterize the dust properties of the FeSt 1-457

core, as well as the relation between the dust and the dense gas, using

Herschel, Planck, 2MASS, ESO Very Large Telescope, APEX-Laboca, and IRAM

30 m data. Methods: We derive maps of submillimeter dust optical

depth and effective dust temperature from Herschel data that were

calibrated against Planck. After calibration, we then fit a modified

blackbody to the long-wavelength Herschel data, using the Planck-derived

dust opacity spectral index β, derived on scales of 30' (or ~1 pc).

We use this model to make predictions of the submillimeter flux density

at 850 μm, and we compare these in turn with APEX-Laboca

observations. Our method takes into account any additive zeropoint

offsets between the Herschel/Planck and Laboca datasets. Additionally,

we compare the dust emission with near-infrared extinction data, and we

study the correlation of high-density-tracing N2H+

emission with the coldest and densest dust in FeSt 1-457.

Results: A comparison of the submillimeter dust optical depth and

near-infrared extinction data reveals evidence for an increased

submillimeter dust opacity at high column densities, interpreted as an

indication of grain growth in the inner parts of the core. Additionally,

a comparison of the Herschel dust model and the Laboca data reveals that

the frequency dependence of the submillimeter opacity, described by the

spectral index β, does not change. A single β that is only

slightly different from the Planck-derived value is sufficient to

describe the data, β = 1.53 ± 0.07. We apply a similar

analysis to Barnard 68, a core with significantly lower column densities

than FeSt 1-457, and we do not find evidence for grain growth but also a

single β. Finally, our previously reported finding of a correlation

of N2H+ emission with lower effective dust

temperatures is confirmed for FeSt 1-457 in mapping observations.

Conclusions: While we find evidence for grain growth from the dust

opacity in FeSt 1-457, we find no evidence for significant variations in

the dust opacity spectral index β on scales 0.02

Organisation(s)

Department of Astrophysics

External organisation(s)

Harvard-Smithsonian Center for Astrophysics, Università degli Studi di Milano-Bicocca, Universidad Nacional Autonoma de Mexico

Journal

Astronomy & Astrophysics

Volume

580

No. of pages

10

ISSN

0004-6361

DOI

https://doi.org/10.1051/0004-6361/201425375

Publication date

08-2015

Peer reviewed

Yes

Austrian Fields of Science 2012

103003 Astronomy, 103004 Astrophysics

Keywords

ASJC Scopus subject areas

Astronomy and Astrophysics, Space and Planetary Science

Portal url

https://ucrisportal.univie.ac.at/en/publications/8feaf12b-6123-45dd-9e25-301f1d0eed20