Cloud fragmentation and proplyd-like features in HII regions imaged by HST

Abstract

We have analyzed HST ACS and WFPC2 new and archival images of eight HII regions to look for new proto-planetary disks (proplyds) similar to those found in the Orion Nebula. We find a wealth of features similar in size (though many are larger) to the bright cusps around the Orion Nebula proplyds. None of them, however, contains a definitive central star. From this, we deduce that the new cusps may not be proplyds, but instead are fragments of molecular cloud material. Out of all the features found in the eight HII regions examined, only one, an apparent edge-on silhouette in M17, may have a central star. This feature might join the small number of bona fide proplyds found outside the Orion Nebula, in M8, M20 and possibly in M16. In line with the results found recently by Smith et al. (2005), the paucity of proplyds outside the Orion Nebula, may be explained by their transient nature as well as by the specific environmental conditions under whichthey can be observed.

51 pages; 19 figures; 5 tables. Accepted by AJ

References in corpus (12)

• A Galactic O-Star Catalog
• New infrared star clusters in the southern Milky Way with 2MASS
• The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turn-offs. II. Results from 12 Galactic Clusters and OB Associations
• The Lifetimes and Evolution of Molecular Cloud Cores
• A Keck High Resolution Spectroscopic Study of the Orion Nebula Proplyds
• A radio catalog of Galactic HII regions for applications from decimeter to millimeter wavelengths
• A Catalogue of infrared star clusters and stellar groups
• Thermal Dust Emission from Proplyds, Unresolved Disks, and Shocks in the Orion Nebula
• An Atlas of Galactic Spectra Observed with the Far Ultraviolet Spectroscopic Explorer
• HST/WFPC2 and VLT/ISAAC observations of PROPLYDS in the giant HII region NGC 3603
• Star clusterings in the Carina complex: UBVRI photometry of NGC 3324 and Loden 165
• HST and UKIRT Observations of the Center of the Trifid Nebula: Evidence for the Photoevaporation of a Proplyd and a Protostellar Condensation

Cited by in corpus (19)

• Interaction of Supernova Ejecta with Nearby Protoplanetary Disks
• Radiation-magnetohydrodynamic simulations of the photoionisation of magnetised globules
• Herschel far-infrared observations of the Carina Nebula complex I: Introduction and global cloud structure
• An X-ray Census of Young Stars in the Massive Southern Star-Forming Complex NGC 6357
• Dusty Wind-Blown Bubbles
• Spitzer Observations of the HII Region NGC 2467: An Analysis of Triggered Star Formation
• Properties of protostars in the Elephant Trunk globule IC 1396A
• Molecular globules in the Veil bubble of Orion. IRAM 30m 12CO, 13CO, and C18O 2-1 expanded maps of Orion A
• Ionized gas diagnostics from protoplanetary discs in the Orion Nebula and the abundance discrepancy problem
• Mass and motion of globulettes in the Rosette Nebula
• The tiny globulettes in the Carina Nebula
• Small-spatial scale variations of nebular properties and the abundance discrepancy in three Galactic HII regions
• A multiwavelength investigation of the HII region S311: Young stellar population and star formation
• A candidate planetary-mass object with a photoevaporating disk in Orion
• Radio observations of globulettes in the Carina Nebula
• Formation of free-floating planetary mass objects via circumstellar disk encounters
• History of Globulettes in the Milky Way
• The Return of the Proplyds - Understanding the Dynamics of Ionization Triggered Stars
• ALMA detection of the dusty object silhouetted against the S0 galaxy NGC 3269 in the Antlia cluster