scholarly journals Photoionization feedback in turbulent molecular clouds

2020 ◽  
Vol 500 (2) ◽  
pp. 1833-1843
Author(s):  
Nina S Sartorio ◽  
Bert Vandenbroucke ◽  
Diego Falceta-Goncalves ◽  
Kenneth Wood
Keyword(s):  
Molecular Clouds ◽  
Source Parameters ◽  
Density Structure ◽  
Star Forming ◽  
Turbulent Statistics ◽  
Model Cloud ◽  
H Ii Region ◽  
A Minor ◽  
2D And 3D ◽  
The Impact

ABSTRACT We present a study of the impact of photoionization feedback from young massive stars on the turbulent statistics of star-forming molecular clouds. This feedback is expected to alter the density structure of molecular clouds and affect future star formation. Using the AMUN-Rad code, we first generate a converged isothermal forced turbulent density structure inside a periodic box. We then insert an ionizing source in this box and inject photoionization energy using a two-temperature pseudo-isothermal equation of state. We study the impact of sources at different locations in the box and of different source luminosities. We find that photoionization has a minor impact on the 2D and 3D statistics of turbulence when turbulence continues to be driven in the presence of a photoionizing source. Photoionization is only able to disrupt the cloud if the turbulence is allowed to decay. In the former scenario, the presence of an H ii region inside our model cloud does not lead to a significant impact on observable quantities, independent of the source parameters.

scholarly journals The atomic hydrogen/molecular cloud association: an unavoidable relationship

1991 ◽  
Vol 147 ◽  
pp. 37-40
Author(s):  
G. Joncas
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Clouds ◽  
Large Scale ◽  
Young Stars ◽  
Physical Processes ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
The Impact

The presence of HI in the interstellar medium is ubiquitous. HI is the principal actor in the majority of the physical processes at work in our Galaxy. Restricting ourselves to the topics of this symposium, atomic hydrogen is involved with the formation of molecular clouds and is one of the byproducts of their destruction by young stars. HI has different roles during a molecular cloud's life. I will discuss here a case of coexisting HI and H2 at large scale and the origin of HI in star forming regions. For completeness' sake, it should be mentionned that there are at least three other aspects of HI involvement: HI envelopes around molecular clouds, the impact of SNRs (see work on IC 443), and the role of HI in quiescent dark clouds (see van der Werf's work).

scholarly journals The atomic hydrogen/molecular cloud association: an unavoidable relationship

1991 ◽  
Vol 147 ◽  
pp. 37-40
Author(s):  
G. Joncas
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Clouds ◽  
Large Scale ◽  
Young Stars ◽  
Physical Processes ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
The Impact

The presence of HI in the interstellar medium is ubiquitous. HI is the principal actor in the majority of the physical processes at work in our Galaxy. Restricting ourselves to the topics of this symposium, atomic hydrogen is involved with the formation of molecular clouds and is one of the byproducts of their destruction by young stars. HI has different roles during a molecular cloud's life. I will discuss here a case of coexisting HI and H2 at large scale and the origin of HI in star forming regions. For completeness' sake, it should be mentionned that there are at least three other aspects of HI involvement: HI envelopes around molecular clouds, the impact of SNRs (see work on IC 443), and the role of HI in quiescent dark clouds (see van der Werf's work).

scholarly journals Characteristics of H2CO Towards Star-Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 171-171
Author(s):  
H. R. Dickel ◽  
W. M. Goss ◽  
A. H. Rots
Keyword(s):  
Molecular Clouds ◽  
H Ii Regions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Compact Region ◽  
Dense Cores ◽  
H Ii Region ◽  
Narrow Width ◽  
Water Masers ◽  
Small Clusters

Small clusters of recently-formed massive stars with their associated compact H II regions are often found embedded in the dense cores of molecular clouds. The H2CO opacity is correlated with the compactness of the H II region and is especially high for those with associated maser activity although additional factors are involved for the ultra-compact H II regions (UCH II). VLA observations of H2CO at 2 cm have been made towards the UCH II regions of W49-north. The highest H2CO opacity of 1.0 is found towards region A which does not have maser activity; yet one of the most compact region C, has an H2CO opacity of only 0.3, For these sources the integrated H2CO opacity (over the entire profile) may be more indicative of compactness. This may be due to the broader H2CO lines which can occur towards the maser regions. For example, large line widths of 10 to 12 km s−1 ate found towards W49-north G where the most intense water masers are located and towards W49-north B which has OH masers. The H2CO line with the highest 2 cm opacity of 2.5 and a narrow width of 2 km s−1 is found towards the UCH II region ON 3 which has only weak H2O maser emission.

scholarly journals Masers in SGR B2: Sites of Star-Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 161-163 ◽  
Author(s):  
J. B. Whiteoak ◽  
F. F. Gardner ◽  
J. R. Forster ◽  
P. Palmer ◽  
V. Pankonin
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Star Forming ◽  
Star Forming Regions ◽  
H Ii Region ◽  
Cloud Complex

H2CO and OH masers in the H II-region/molecular-cloud complex Sgr B2 have been observed with the VLA and combined with other observations of OH and H2O masers. It is found that groups of the masers and compact continuum components are located along a north-south line extending across the complex. The overall alignment suggests that star formation is being triggered by a single large-scale event such as an interaction between molecular clouds.

scholarly journals Structure and expansion law of H ii regions in structured molecular clouds

2019 ◽  
Vol 487 (2) ◽  
pp. 2200-2214 ◽  
Author(s):  
Manuel Zamora-Avilés ◽  
Enrique Vázquez-Semadeni ◽  
Ricardo F González ◽  
José Franco ◽  
Steven N Shore ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Massive Star ◽  
Mean Value ◽  
Neutral Medium ◽  
H Ii Regions ◽  
Star Forming ◽  
Star Forming Regions ◽  
H Ii Region ◽  
Analytical Result ◽  
Magnetohydrodynamic Simulations

Abstract We present radiation-magnetohydrodynamic simulations aimed at studying evolutionary properties of H ii regions in turbulent, magnetized, and collapsing molecular clouds formed by converging flows in the warm neutral medium. We focus on the structure, dynamics, and expansion laws of these regions. Once a massive star forms in our highly structured clouds, its ionizing radiation eventually stops the accretion (through filaments) towards the massive star-forming regions. The new overpressured H ii regions push away the dense gas, thus disrupting the more massive collapse centres. Also, because of the complex density structure in the cloud, the H ii regions expand in a hybrid manner: they virtually do not expand towards the densest regions (cores), while they expand according to the classical analytical result towards the rest of the cloud, and in an accelerated way, as a blister region, towards the diffuse medium. Thus, the ionized regions grow anisotropically, and the ionizing stars generally appear off-centre of the regions. Finally, we find that the hypotheses assumed in standard H ii-region expansion models (fully embedded region, blister-type, or expansion in a density gradient) apply simultaneously in different parts of our simulated H ii regions, producing a net expansion law (R∝ tα, with α in the range of 0.93–1.47 and a mean value of 1.2 ± 0.17) that differs from any of those of the standard models.

scholarly journals The Impact of Metabolic Scion–Rootstock Interactions in Different Grapevine Tissues and Phloem Exudates

Metabolites ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 349
Author(s):  
Sara Tedesco ◽  
Alexander Erban ◽  
Saurabh Gupta ◽  
Joachim Kopka ◽  
Pedro Fevereiro ◽  
...  
Keyword(s):  
Agronomic Traits ◽  
Phloem Exudate ◽  
Graft Union ◽  
Reciprocal Effect ◽  
Metabolic Markers ◽  
Interaction Studies ◽  
Metabolic Interactions ◽  
A Minor ◽  
The Impact ◽  
Related Compounds

In viticulture, grafting is used to propagate Phylloxera-susceptible European grapevines, thereby using resistant American rootstocks. Although scion–rootstock reciprocal signaling is essential for the formation of a proper vascular union and for coordinated growth, our knowledge of graft partner interactions is very limited. In order to elucidate the scale and the content of scion–rootstock metabolic interactions, we profiled the metabolome of eleven graft combination in leaves, stems, and phloem exudate from both above and below the graft union 5–6 months after grafting. We compared the metabolome of scions vs. rootstocks of homografts vs. heterografts and investigated the reciprocal effect of the rootstock on the scion metabolome. This approach revealed that (1) grafting has a minor impact on the metabolome of grafted grapevines when tissues and genotypes were compared, (2) heterografting affects rootstocks more than scions, (3) the presence of a heterologous grafting partner increases defense-related compounds in both scion and rootstocks in shorter and longer distances from the graft, and (4) leaves were revealed as the best tissue to search for grafting-related metabolic markers. These results will provide a valuable metabolomics resource for scion–rootstock interaction studies and will facilitate future efforts on the identification of metabolic markers for important agronomic traits in grafted grapevines.

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

Sign in / Sign up

Export Citation Format

Share Document