Triggered massive-star formation on the borders of Galactic H II regions

Zavagno, A.; Deharveng, L.; Comerón, F.; Brand, J.; Massi, F.; Caplan, J.; Russeil, D.

doi:10.1051/0004-6361:20053952

Cited by 160 publications

(186 citation statements)

References 64 publications

(45 reference statements)

Supporting

Mentioning

171

Contrasting

Unclassified

Order By: Relevance

“…(This mechanism is often called "radiation-driven implosion" of a condensation, but "radiationdriven compression" would be better as no observations indicate that star formation occurs during the implosion.) Good illustrations of star formation triggered by the expansion of H ii regions are given by the RCW 79 (Zavagno et al 2006) and RCW 120 ) bubbles.…”

Section: The Neutral Environment Of the Bubbles As Seen By Atlasgalmentioning

confidence: 99%

A gallery of bubbles

Deharveng

Schüller

Anderson

et al. 2010

A&A

Self Cite

359

584

View full text Add to dashboard Cite

Context. This study deals with infrared bubbles, the H ii regions they enclose, and triggered massive-star formation on their borders.Aims. We attempt to determine the nature of the bubbles observed by Spitzer in the Galactic plane, mainly to establish if possible their association with massive stars. We take advantage of the very simple morphology of these objects to search for star formation triggered by H ii regions, and to estimate the importance of this mode of star formation.Methods. We consider a sample of 102 bubbles detected by Spitzer-GLIMPSE, and catalogued by Churchwell et al. (2006; hereafter CH06). We use mid-infrared and radio-continuum public data (respectively the Spitzer-GLIMPSE and -MIPSGAL surveys and the MAGPIS and VGPS surveys) to discuss their nature. We use the ATLASGAL survey at 870 μm to search for dense neutral material collected on their borders. The 870 μm data traces the distribution of cold dust, thus of the dense neutral material where stars may form. Results. We find that 86% of the bubbles contain ionized gas detected by means of its radio-continuum emission at 20-cm. Thus, most of the bubbles observed at 8.0 μm enclose H ii regions ionized by O-B2 stars. This finding differs from the earlier CH06 results (∼25% of the bubbles enclosing H ii regions). Ninety-eight percent of the bubbles exhibit 24 μm emission in their central regions. The ionized regions at the center of the 8.0 μm bubbles seem to be devoid of PAHs but contain hot dust. PAH emission at 8.0 μm is observed in the direction of the photodissociation regions surrounding the ionized gas. Among the 65 regions for which the angular resolution of the observations is high enough to resolve the spatial distribution of cold dust at 870 μm, we find that 40% are surrounded by cold dust, and that another 28% contain interacting condensations. The former are good candidates for the collect and collapse process, as they display an accumulation of dense material at their borders. The latter are good candidates for the compression of pre-existing condensations by the ionized gas. Thirteen bubbles exhibit associated ultracompact H ii regions in the direction of dust condensations adjacent to their ionization fronts. Another five show methanol masers in similar condensations. Conclusions. Our results suggest that more than a quarter of the bubbles may have triggered the formation of massive objects.Therefore, star formation triggered by H ii regions may be an important process, especially for massive-star formation.

show abstract

Section: The Neutral Environment Of the Bubbles As Seen By Atlasgalmentioning

confidence: 99%

A gallery of bubbles

Deharveng

Schüller

Anderson

et al. 2010

A&A

Self Cite

359

584

View full text Add to dashboard Cite

show abstract

“…Several H ii regions have been studied individually in the context of triggered Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. star formation, focusing on the associated neutral material and the young stellar population (Zavagno et al 2006;Deharveng et al 2009;Pomarès et al 2009;Bieging et al 2009). These studies have shown that the expansion of H ii regions can trigger the formation of new stars of all masses.…”

Section: Introductionmentioning

confidence: 99%

Star formation triggered by H II regions in our Galaxy

Zavagno¹,

Anderson²,

Russeil³

et al. 2010

A&A

Self Cite

View full text Add to dashboard Cite

Context. It has been shown that by means of different physical mechanisms the expansion of H ii regions can trigger the formation of new stars of all masses. This process may be important to the formation of massive stars but has never been quantified in the Galaxy. Aims. We use Herschel-PACS and -SPIRE images from the Herschel infrared survey of the Galactic plane, Hi-GAL, to perform this study. Methods. We combine the Spitzer-GLIMPSE and -MIPSGAL, radio-continuum and submillimeter surveys such as ATLASGAL with Hi-GAL to study young stellar objects (YSOs) observed towards Galactic H ii regions. We select a representative H ii region, N49, located in the field centered on l = 30 • observed as part of the Hi-GAL science demonstration phase, to demonstrate the importance Hi-GAL will have to this field of research. Results. Hi-GAL PACS and SPIRE images reveal a new population of embedded young stars, coincident with bright ATLASGAL condensations. The Hi-GAL images also allow us, for the first time, to constrain the physical properties of the newly formed stars by means of fits to their spectral energy distribution. Massive young stellar objects are observed at the borders of the N49 region and represent second generation massive stars whose formation has been triggered by the expansion of the ionized region. Conclusions. The first Hi-GAL images obtained using PACS and SPIRE have demonstrated the capability to investigate star formation triggered by H ii regions. With radio, submillimeter, and shorter wavelength infrared data from other surveys, the Hi-GAL images reveal young massive star-forming clumps surrounding the perimeter of the N49 H ii generated bubble. Hi-GAL enables us to detect a population of young stars at different evolutionary stages, cold condensations only being detected in the SPIRE wavelength range. The far IR coverage of Hi-GAL strongly constrains the physical properties of the YSOs. The large and unbiased spatial coverage of this survey offers us a unique opportunity to lead, for the first time, a global study of star formation triggered by H ii regions in our Galaxy.

show abstract

“…3.4), we use the analytical model of Whitworth et al (1994) for the case of an expanding Hii region which predicts the time at which the fragmentation occurs. We have followed the analysis of Zavagno et al (2006), deriving the time when the fragmentation may have occurred (t frag ), and the size of the Hii region at t frag (R frag ), given by t frag = 1.56 a 0. …”

Section: Triggered Star Formation Scenariomentioning

confidence: 99%

“…The derived value of n 0 is higher than the density limits required for the fragmentation according to the Whitworth et al scenario, which indicates that the C&C process might be important in the collected layers of molecular gas. As pointed out by Zavagno et al (2006), the estimates presented above are rough, since the Whitworth et al model assumes expansion into a homogeneous medium and many uncertainties remain concerning to the uniformity of the medium where Gum 31 evolved (see Sect. 3.1).…”

Section: Triggered Star Formation Scenariomentioning

confidence: 99%

870μm continuum observations of the bubble-shaped nebula Gum 31

Duronea

Vasquez

Gómez

et al. 2015

A&A

View full text Add to dashboard Cite

Aims. We present here a study of the cold dust in the close environs of the ring nebula Gum 31. We aim at deriving the physical properties of the molecular gas and dust associated with the nebula, and investigating its correlation with the star formation in the region, which was probably triggered by the expansion of the ionization front against its environment. Methods. We make use of 870 μm emission data obtained with the Large APEX Bolometer Camera (LABOCA) to map the dust emission. The 870 μm emission provides an excellent probe of mass and density of dense molecular clouds. The obtained LABOCA image was compared to archival infrared, radio continuum, and optical images. Results. The 870 μm emission follows the 8 μm (Spitzer), 250 μm, and 500 μm (Herschel) emission distributions showing the classical morphology of a two-dimensional projection of a spherical shell. We use the 870 μm and 250 μm images to identify 60 dust clumps in the collected layers of molecular gas using the Gaussclumps algorithm. The clumps have effective deconvolved radii between 0.16 pc and 1.35 pc, masses between 70 M and 2800 M , and volume densities between 1.1 × 10 3 cm −3 and ∼2.04× 10 5 cm −3 . The total mass of the clumps is ∼37 600 M . The dust temperature of the clumps is in the range from 21 K to 32 K, while inside the Hii region it reaches ∼40 K. The clump mass distribution for the sample is fitted by a power law dN/dlog(M/M ) ∝ M −α , with α = 0.93± 0.28. The slope differs from those obtained for the stellar IMF in the solar neighborhood, suggesting that the clumps are not direct progenitors of single stars/protostars. The mass-radius relationship for the 41 clumps detected in the 870 μm emission shows that only 37% of them lie in or above the high-mass star formation threshold. Most of this 37% have candidate YSOs projected inside their limits. A comparison of the dynamical age of the Hii region with the fragmentation time, allowed us to conclude that the collect-and-collapse mechanism may be important for the star formation at the edge of Gum 31, although other processes may be acting simultaneously. The position of the identified young stellar objects in the region is also a strong indicator that the collect-and-collapse process is acting.

show abstract

Triggered massive-star formation on the borders of Galactic H II regions

Cited by 160 publications

References 64 publications

A gallery of bubbles

A gallery of bubbles

Star formation triggered by H II regions in our Galaxy

870μm continuum observations of the bubble-shaped nebula Gum 31

Contact Info

Product

Resources

About