* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: Barnard 59


L

Posts: 131433
Date:
RE: Barnard 59
Permalink  
 


Ceci N'est Pas Une Pipe

eso1233a.jpg

Just as René Magritte wrote "This is not a pipe" on his famous painting, this is also not a pipe. It is however a picture of part of a vast dark cloud of interstellar dust called the Pipe Nebula. This new and very detailed image of what is also known as Barnard 59 was captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory. By coincidence this image is appearing on the 45th anniversary of the painter/s death.
Read more



__________________


L

Posts: 131433
Date:
Permalink  
 

Title: The role of theta Oph in the formation and evolution of the Pipe Nebula - is star formation ever isolated?
Authors: Matthias Gritschneder, Douglas N. C. Lin

We propose that the Pipe Nebula is an HII region shell swept up by the B2 IV beta Cephei star theta Ophiuchi. After reviewing the morphological evidence by recent observations, we perform a series of analytical calculations. We use realistic HII region parameters derived with the radiative transfer code Cloudy from observed stellar parameters. We are able to show that the current size, mass and pressure of the region can be explained in this scenario. We investigate the configuration today and come to the conclusion that the Pipe Nebula can be best described by a three phase medium in pressure equilibrium. The pressure support is provided by the ionised gas and mediated by an atomic component to confine the cores at the observed current pressure. In the future, star formation in these cores is likely to be either triggered by feedback of the most massive, gravitationally bound cores as soon as they collapse or by the supernova explosion of theta Ophiuchi itself.

Read more (1296kb, PDF)



__________________


L

Posts: 131433
Date:
Pipe Nebula
Permalink  
 


Title: The molecular gas content of the Pipe Nebula I. Direct evidence of outflow-generated turbulence in B59?
Authors: A. Duarte-Cabral, A. Chrysostomou, N. Peretto, G. A. Fuller, B. Matthews, G. Schieven, G. R. Davis

The Pipe Nebula is a molecular cloud hosting the B59 region as its only active star-forming clump. While the particular importance of outflows in active star forming regions is subject of debate, the quiet nature of the gas in B59 makes it a good site to directly see the impact of protostellar feedback on the quiescent dense gas. Using HARP at the JCMT, we mapped the B59 region with the J=3-2 transition of 12CO to study the kinematics and energetics of the outflows, and 13CO and C18O to study the overall dynamics of the ambient cloud, the physical properties of the gas, and the hierarchical structure of the region. The B59 region has a total of 30Msun of cold and quiescent material, mostly gravitationally bound, with narrow line widths throughout. Such low levels of turbulence in non-star-forming sites of B59 are indicative of the intrinsic initial conditions of the cloud. On the other hand, close to the forming protostars the impact of the outflows is observed as a localised increase of both line widths from 0.3 km/s to 1 km/s, and 13CO excitation temperatures by 2-3K. The impact of the outflows is also evident in the low column density material which shows signs of being pushed, shaped and carved by the outflow bow shocks as they pierce their way out of the cloud. Much of this structure is readily apparent in a dendrogram analysis of the cloud. B59's low mass, intrinsically quiescent gas and small number of protostars, allows the identification of specific regions of the outflows' interaction with the dense gas. Our study suggests that outflows are an important mechanism in injecting and sustaining supersonic turbulence at sub-parsec scales. We find that only a fraction of the outflow energy is deposited as turbulent energy of the gas. This turbulent energy is sufficient to slow down the collapse of the region.

Read more (4617kb, PDF)



__________________


L

Posts: 131433
Date:
The Pipe Nebula
Permalink  
 


Title: The Pipe Nebula as seen with Herschel: Formation of filamentary structures by large-scale compression ?
Authors: N. Peretto, Ph. Andre, V. Konyves, N. Schneider, D. Arzoumanian, P. Palmeirim, P. Didelon, M. Attard, J.P. Bernard, J. Di Francesco, D. Elia, M. Hennemann, T. Hill, J. Kirk, A. Men'shchikov, F. Motte, Q. Nguyen Luong, H. Roussel, T. Sousbie, L. Testi, D. Ward-Thompson, G. J. White, A. Zavagno

A growing body of evidence indicates that the formation of filaments in interstellar clouds is a key component of the star formation process. In this paper, we present new Herschel PACS and SPIRE observations of the B59 and Stem regions in the Pipe Nebula complex, revealing a rich, organized network of filaments. The asymmetric column density profiles observed for several filaments, along with the bow-like edge of B59, indicates that the Pipe Nebula is being compressed from its western side, most likely by the winds from the nearby Sco OB2 association. We suggest that this compressive flow has contributed to the formation of some of the observed filamentary structures. In B59, the only region of the entire Pipe complex showing star formation activity, the same compressive flow has likely enhanced the initial column density of the clump, allowing it to become globally gravitationally unstable. Although more speculative, we propose that gravity has also been responsible for shaping the converging filamentary pattern observed in B59. While the question of the relative impact of large-scale compression and gravity remains open in B59, large-scale compression appears to be a plausible mechanism for the initial formation of filamentary structures in the rest of the complex

Read more (3355kb, PDF)



__________________


L

Posts: 131433
Date:
RE: Barnard 59
Permalink  
 


Title: Barnard 59: No Evidence for Further Fragmentation
Authors: C. G. Román-Zúńiga, P. Frau, J. M. Girart, J. F. Alves

The dense molecular clump at the center of the Barnard 59 (B59) complex is the only region in the Pipe Nebula that has formed a small, stellar cluster. The previous analysis of a high resolution near-IR dust extinction map revealed that the nuclear region in B59 is a massive, mostly quiescent clump of 18.9 solar masses. The clump shows a monolithic profile, possibly indicating that the clump is on the way to collapse, with no evident fragmentation that could lead to another group of star systems. In this paper we present new analysis that compares the dust extinction map with a new dust emission radio-continuum map of higher spatial resolution. We confirm that the clump does not show any significant evidence for prestellar fragmentation at scales smaller than those probed previously.

Read more (380kb, PDF)



__________________


L

Posts: 131433
Date:
Permalink  
 

Title: Chemical Differentiation toward the Pipe Nebula Starless Cores
Authors: P. Frau (1), J.M. Girart (1), M. T. Beltran (2) ((1) Institut de Cičncies de l'Espai (CSIC-IEEC), (2) INAF-Osservatorio Astrofisico di Arcetri)

We used the new IRAM 30-m FTS backend to perform an unbiased ~15 GHz wide survey at 3 mm toward the Pipe Nebula young diffuse starless cores. We found an unexpectedly rich chemistry. We propose a new observational classification based on the 3 mm molecular line emission normalised by the core visual extinction (Av). Based on this classification, we report a clear differentiation in terms of chemical composition and of line emission properties, which served to define three molecular core groups. The "diffuse" cores, Av~22, show typical evolved chemistry prior to the onset of the star formation process, with nitrogenated and deuterated species, as well as carbon chain molecules. Based on these categories, one of the "diffuse" cores (Core 47) has the spectral line properties of the "oxo-sulfurated" ones, which suggests that it is a possible failed core.

Read more (287kb, PDF)



__________________


L

Posts: 131433
Date:
Pipe Nebula
Permalink  
 


Title: A Spitzer Census of Star Formation Activity in the Pipe Nebula
Authors: Jan Forbrich, Charles J. Lada, August A. Muench, Joăo Alves, Marco Lombardi

The Pipe Nebula, a large nearby molecular cloud lacks obvious signposts of star formation in all but one of more than 130 dust extinction cores that have been identified within it. In order to quantitatively determine the current level of star formation activity in the Pipe Nebula, we analysed 13 square degrees of sensitive mid-infrared maps of the entire cloud, obtained with the Multiband Imaging Photometer for Spitzer (MIPS) at wavelengths of 24 micron and 70 micron to search for candidate Young Stellar Objects (YSOs) in the high-extinction regions. We argue that our search is complete for class I and typical class II YSOs with luminosities of Lbol~0.2 Lo and greater. We find only 18 candidate YSOs in the high-extinction regions of the entire Pipe cloud. Twelve of these sources are previously known members of a small cluster associated with Barnard 59, the largest and most massive dense core in the cloud. With only six candidate class I and class II YSOs detected towards extinction cores outside of this cluster, our findings emphatically confirm the notion of an extremely low level of star formation activity in the Pipe Nebula. The resulting star formation efficiency for the entire cloud mass is only ~0.06 %.

Read more (1846kb, PDF)

__________________


L

Posts: 131433
Date:
Barnard 59
Permalink  
 


Title: High Resolution Near-Infrared Survey of the Pipe Nebula I: A Deep Infrared Extinction Map of Barnard 59
Authors: Carlos G. Román-Zúńiga, Charles J. Lada, Joăo F. Alves

We present our analysis of a fully sampled, high resolution dust extinction map of the Barnard 59 complex in the Pipe Nebula. The map was constructed with the infrared colour excess technique applied to a photometric catalogue that combines data from both ground and space based observations. The map resolves for the first time the high density center of the main core in the complex, that is associated with the formation of a small cluster of stars. We found that the central core in Barnard 59 shows an unexpected lack of significant substructure consisting of only two significant fragments. Overall, the material appears to be consistent with being a single, large core with a density profile that can be well fit by a King model. A series of NH_3 pointed observations towards the high column density center of the core appear to show that the core is still thermally dominated, with sub-sonic non-thermal motions. The stars in the cluster could be providing feedback to support the core against collapse, but the relatively narrow radio lines suggest that an additional source of support, for example a magnetic field, may be required to stabilise the core. Outside the central core our observations reveal the structure of peripheral cores and resolve an extended filament into a handful of significant substructures whose spacing and masses appear to be consistent with Jeans fragmentation.

Read more (2276kb, PDF)

__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard