J/A+A/616/A78 Dust extinction map of the Nessie filament (Mattern+, 2018)
Structure and fragmentation of a high line-mass filament: Nessie.
Mattern M., Kainulainen J., Zhang M., Beuther H.
<Astron. Astrophys. 616, A78 (2018)>
=2018A&A...616A..78M 2018A&A...616A..78M (SIMBAD/NED BibCode)
ADC_Keywords: Diffuse clouds ; Extinction ; Interstellar medium ;
Molecular clouds ; Reddening
Keywords: stars: formation - infrared: ISM - ISM: clouds - dust, extinction
Abstract:
An increasing number of hundred-parsec scale, high line-mass filaments
have been detected in the Galaxy. Their evolutionary path, including
fragmentation towards star formation, is virtually unknown. We
characterize the fragmentation within the Nessie filament, covering
size-scales between 0.1-100pc. We also connect the small-scale
fragments to the star-forming potential of the cloud. We combine
near-infrared data from the VVV survey with mid-infrared GLIMPSE data
to derive a high-resolution dust extinction map and apply a wavelet
decomposition technique on it to analyze the fragmentation
characteristics of the cloud, which are compared with predictions from
fragmentation models. We compare the detected objects to those
identified in 10 times coarser resolution from ATLASGAL data. We
present a high-resolution extinction map of Nessie. We estimate the
mean line-mass of Nessie to be 627M☉/pc and the distance to be
3.5kpc. We find that Nessie shows fragmentation at multiple size
scales. The nearest-neighbour separations of the fragments at all
scales are within a factor of 2 of the Jeans' length at that scale.
However, the relationship between the mean densities of the fragments
and their separations is significantly shallower than expected for
Jeans' fragmentation. The relationship is similar to the one predicted
for a filament that exhibits a Larson-like scaling between size-scale
and velocity dispersion; such a scaling may result from turbulent
support. Based on the number of YSOs in Nessie, we estimate that the
star formation rate is 371M☉/Myr; similar values result if using
the number of dense cores, or the amount of dense gas, as the proxy of
star formation. The star formation efficiency is 0.017. These numbers
indicate that Nessie's star-forming content is comparable to the Solar
neighborhood giant molecular clouds like Orion A.
Description:
Combined near- and mid-infrared dust extinction map of the so called
Nessie filament, located at about 338.5° galactic longitude and
-0.3° galactic latitude. The visual extinction (Av) is given in
mag. Positions without measurement are flaged as nan values.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 155 1 Information on fits image
fits/* . 1 Fits image
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude of center (J2000)
21- 23 F3.1 arcsec/pix scale Scale of the image
25- 28 I4 --- Nx Number of pixels along X-axis
30- 33 I4 --- Ny Number of pixels along Y-axis
35- 39 I5 Kibyte size Size of FITS file
41- 70 A30 --- FileName Name of FITS file, in subdirectory fits
72-155 A84 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Michael Mattern, mmattern(at)mpifr-bonn.mpg.de
(End) Michael Mattern [MPIfR, Germany], Patricia Vannier [CDS] 03-May-2018