scholarly journals The headlight cloud in NGC 628: An extreme giant molecular cloud in a typical galaxy disk

2020 ◽  
Vol 634 ◽  
pp. A121 ◽  
Author(s):  
Cinthya N. Herrera ◽  
Jérôme Pety ◽  
Annie Hughes ◽  
Sharon E. Meidt ◽  
Kathryn Kreckel ◽  
...  
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Stellar Population ◽  
High Mass ◽  
Molecular Gas ◽  
Giant Molecular Cloud ◽  
The Impact

Context. Cloud-scale surveys of molecular gas reveal the link between giant molecular cloud properties and star formation across a range of galactic environments. Cloud populations in galaxy disks are considered to be representative of the normal star formation process, while galaxy centers tend to harbor denser gas that exhibits more extreme star formation. At high resolution, however, molecular clouds with exceptional gas properties and star formation activity may also be observed in normal disk environments. In this paper we study the brightest cloud traced in CO(2–1) emission in the disk of nearby spiral galaxy NGC 628. Aims. We characterize the properties of the molecular and ionized gas that is spatially coincident with an extremely bright H II region in the context of the NGC 628 galactic environment. We investigate how feedback and large-scale processes influence the properties of the molecular gas in this region. Methods. High-resolution ALMA observations of CO(2–1) and CO(1−0) emission were used to characterize the mass and dynamical state of the “headlight” molecular cloud. The characteristics of this cloud are compared to the typical properties of molecular clouds in NGC 628. A simple large velocity gradient (LVG) analysis incorporating additional ALMA observations of 13CO(1−0), HCO+(1−0), and HCN(1−0) emission was used to constrain the beam-diluted density and temperature of the molecular gas. We analyzed the MUSE spectrum using Starburst99 to characterize the young stellar population associated with the H II region. Results. The unusually bright headlight cloud is massive (1 − 2 × 107 M⊙), with a beam-diluted density of nH2 = 5 × 104 cm−3 based on LVG modeling. It has a low virial parameter, suggesting that the CO emission associated with this cloud may be overluminous due to heating by the H II region. A young (2 − 4 Myr) stellar population with mass 3 × 105 M⊙ is associated. Conclusions. We argue that the headlight cloud is currently being destroyed by feedback from young massive stars. Due to the large mass of the cloud, this phase of the its evolution is long enough for the impact of feedback on the excitation of the gas to be observed. The high mass of the headlight cloud may be related to its location at a spiral co-rotation radius, where gas experiences reduced galactic shear compared to other regions of the disk and receives a sustained inflow of gas that can promote the mass growth of the cloud.

scholarly journals CO (J=2-1) Observations of the Molecular Cloud Complex in the Galactic Center

1994 ◽  
Vol 140 ◽  
pp. 168-169
Author(s):  
Tomoharu Oka ◽  
Tetsuo Hasegawa ◽  
Masahiko Hayashi ◽  
Toshihiro Handa ◽  
Sei'ichi Sakamoto
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Galactic Center ◽  
Molecular Gas ◽  
Star Forming ◽  
Near Future ◽  
Cloud Complex ◽  
Mapping Observation

AbstractWe report a large scale mapping observation of the Galactic center region in the CO (J=2-1) line using the Tokyo-NRO 60cm survey telescope. Distribution of the CO (J=2-1) emission in the I-V plane suggests that molecular clouds forms a huge complex (Nuclear Molecular cloud Complex, NMC). Tracers of star formation activities in the last 106-108 years show that star formation has occured in a ring ~ 100 pc in radius. Relative to this Star Forming Ring, the molecular gas is distributed mainly on the positive longitude side. This may indicate that much of the gas in NMC is in transient orbit to fall into the star forming ring or to the nucleus in the near future.

scholarly journals ALMA CO observations of a giant molecular cloud in M 33: Evidence for high-mass star formation triggered by cloud–cloud collisions

2020 ◽  
Author(s):  
Hidetoshi Sano ◽  
Kisetsu Tsuge ◽  
Kazuki Tokuda ◽  
Kazuyuki Muraoka ◽  
Kengo Tachihara ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Line Emission ◽  
High Mass ◽  
H Ii Regions ◽  
Mass Star ◽  
Star Forming ◽  
Spatially Resolved ◽  
Giant Molecular Cloud

Abstract We report the first evidence for high-mass star formation triggered by collisions of molecular clouds in M 33. Using the Atacama Large Millimeter/submillimeter Array, we spatially resolved filamentary structures of giant molecular cloud 37 in M 33 using 12CO(J = 2–1), 13CO(J = 2–1), and C18O(J = 2–1) line emission at a spatial resolution of ∼2 pc. There are two individual molecular clouds with a systematic velocity difference of ∼6 km s−1. Three continuum sources representing up to ∼10 high-mass stars with spectral types of B0V–O7.5V are embedded within the densest parts of molecular clouds bright in the C18O(J = 2–1) line emission. The two molecular clouds show a complementary spatial distribution with a spatial displacement of ∼6.2 pc, and show a V-shaped structure in the position–velocity diagram. These observational features traced by CO and its isotopes are consistent with those in high-mass star-forming regions created by cloud–cloud collisions in the Galactic and Magellanic Cloud H ii regions. Our new finding in M 33 indicates that cloud–cloud collision is a promising process for triggering high-mass star formation in the Local Group.

scholarly journals Molecules as tracers of galaxy evolution

2012 ◽  
Vol 8 (S292) ◽  
pp. 199-208 ◽  
Author(s):  
Susanne Aalto
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
High Resolution ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Short Review ◽  
Stimulated Emission ◽  
Molecular Gas ◽  
Infrared Galaxies ◽  
Luminous Infrared Galaxies

AbstractStudying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of star formation and the growth of supermassive black holes. We can use molecules as observational tools exploiting them as tracers of chemical, physical and dynamical conditions. In this short review, key molecules (e.g. HCN, HCO+, HNC, HC3N, CN, H3O+) in identifying the nature of buried activity and its evolution are discussed including some standard astrochemical scenarios. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies (LIRGs) allowing us to get past the optically thick dust barrier of the compact obscured nuclei, e.g. in the dusty LIRG NGC4418. High resolution studies are often necessary to separate effects of excitation and radiative transport from those of chemistry - one example is absorption and effects of stimulated emission in the ULIRG Arp220. Finally, molecular gas in large scale galactic outflows is briefly discussed.

scholarly journals Molecular and ionized gas kinematics in the GC Radio Arc

2016 ◽  
Vol 11 (S322) ◽  
pp. 133-136
Author(s):  
N. Butterfield ◽  
C.C. Lang ◽  
E. A. C. Mills ◽  
D. Ludovici ◽  
J. Ott ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Radio Continuum ◽  
Molecular Gas ◽  
The South ◽  
Ionized Gas ◽  
Molecular Emission ◽  
Gas Kinematics

AbstractWe present NH3 and H64α+H63α VLA observations of the Radio Arc region, including the M0.20 – 0.033 and G0.10 – 0.08 molecular clouds. These observations suggest the two velocity components of M0.20 – 0.033 are physically connected in the south. Additional ATCA observations suggest this connection is due to an expanding shell in the molecular gas, with the centroid located near the Quintuplet cluster. The G0.10 – 0.08 molecular cloud has little radio continuum, strong molecular emission, and abundant CH3OH masers, similar to a nearby molecular cloud with no star formation: M0.25+0.01. These features detected in G0.10 – 0.08 suggest dense molecular gas with no signs of current star formation.

scholarly journals FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). VIII. Possible evidence of cloud–cloud collisions triggering high-mass star formation in the giant molecular cloud M 16 (Eagle Nebula)

2020 ◽  
Author(s):  
Atsushi Nishimura ◽  
Shinji Fujita ◽  
Mikito Kohno ◽  
Daichi Tsutsumi ◽  
Tetsuhiro Minamidani ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Velocity Structure ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Collision Event ◽  
Giant Molecular Cloud ◽  
Eagle Nebula ◽  
H Ii Region

Abstract M 16, the Eagle Nebula, is an outstanding H ii region which exhibits extensive high-mass star formation and hosts remarkable “pillars.” We herein obtained new 12COJ = 1–0 data for the region observed with NANTEN2, which were combined with the 12COJ = 1–0 data obtained using the FOREST unbiased galactic plane imaging with Nobeyama 45 m telescope (FUGIN) survey. These observations revealed that a giant molecular cloud (GMC) of ∼1.3 × 105 M⊙ is associated with M 16, which extends for 30 pc perpendicularly to the galactic plane, at a distance of 1.8 kpc. This GMC can be divided into the northern (N) cloud, the eastern (E) filament, the southeastern (SE) cloud, the southeastern (SE) filament, and the southern (S) cloud. We also found two velocity components (blueshifted and redshifted components) in the N cloud. The blueshifted component shows a ring-like structure, and the redshifted one coincides with the intensity depression of the ring-like structure. The position–velocity diagram of the components showed a V-shaped velocity feature. The spatial and velocity structures of the cloud indicated that two different velocity components collided with each other at a relative velocity of 11.6 km s−1. The timescale of the collision was estimated to be ∼4 × 105 yr. The collision event reasonably explains the formation of the O9V star ALS 15348, as well as the shape of the Spitzer bubble N19. A similar velocity structure was found in the SE cloud, which is associated with the O7.5V star HD 168504. In addition, the complementary distributions of the two velocity components found in the entire GMC suggested that the collision event occurred globally. On the basis of the above results, we herein propose a hypothesis that the collision between the two components occurred sequentially over the last several 106 yr and triggered the formation of O-type stars in the NGC 6611 cluster in M 16.

scholarly journals Star Formation in the NGC 2071 Molecular Cloud

1989 ◽  
Vol 120 ◽  
pp. 128-128
Author(s):  
N.J. Evans
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Density Distribution ◽  
Molecular Cloud ◽  
Large Scale ◽  
Far Infrared ◽  
Infrared Emission ◽  
Molecular Outflow ◽  
Broad Array ◽  
Coherent Picture

The NGC 2071 molecular cloud has been studied with a broad array of techniques, including a large scale study of CS emission, high resolution scans in the far-infrared, N H3 studies with the VLA, and near-infrarred imaging. The far-infrared emission constrains the density distribution to fall off approximately as r−1. The NH3 data strongly supports the presence of a disk oriented perpendicular to the molecular outflow, while the CS emission indicates the presence of dense gas in the region. The results will be combined into a coherent picture of this region of current star formation and molecular outflow.

scholarly journals G.A.S.

2019 ◽  
Vol 627 ◽  
pp. A131 ◽  
Author(s):  
M. Cousin ◽  
P. Guillard ◽  
M. D. Lehnert
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Large Scale ◽  
Spatial Scales ◽  
Turbulent Energy ◽  
Stellar Mass ◽  
High Mass ◽  
Radiative Cooling ◽  
The Impact ◽  
Good Agreement

Context. Star formation in galaxies is inefficient, and understanding how star formation is regulated in galaxies is one of the most fundamental challenges of contemporary astrophysics. Radiative cooling, feedback from supernovae and active galactic nuclei (AGN), and large-scale dynamics and dissipation of turbulent energy act over various time and spatial scales and all regulate star formation in a complex gas cycle. Aims. This paper presents the physics implemented in a new semi-analytical model of galaxy formation and evolution called the Galaxy Assembler from dark-matter Simulation (G.A.S.). Methods. The fundamental underpinning of our new model is the development of a multiphase interstellar medium (ISM) in which energy produced by supernovae and AGN maintains an equilibrium between a diffuse, hot, and stable gas and a cooler, clumpy, and low-volume filling factor gas. The hot gas is susceptible to thermal and dynamical instabilities. We include a description of how turbulence leads to the formation of giant molecular clouds through an inertial turbulent energy cascade, assuming a constant kinetic energy transfer per unit volume. We explicitly modelled the evolution of the velocity dispersion at different scales of the cascade and accounted for thermal instabilities in the hot halo gas. Thermal instabilities effectively reduce the impact of radiative cooling and moderates accretion rates onto galaxies, and in particular, for those residing in massive haloes. Results. We show that rapid and multiple exchanges between diffuse and unstable gas phases strongly regulates star formation rates in galaxies because only a small fraction of the unstable gas is forming stars. We checked that the characteristic timescales describing the gas cycle, gas depletion timescale, and star-forming laws at different scales are in good agreement with observations. For high-mass haloes and galaxies, cooling is naturally regulated by the growth of thermal instabilities, so we do not need to implement strong AGN feedback in this model. Our results are also in good agreement with the observed stellar mass function from z ≃ 6.0 to z ≃ 0.5. Conclusion. Our model offers the flexibility to test the impact of various physical processes on the regulation of star formation on a representative population of galaxies across cosmic times. Thermal instabilities and the cascade of turbulent energy in the dense gas phase introduce a delay between gas accretion and star formation, which keeps galaxy growth inefficient in the early Universe. The main results presented in this paper, such as stellar mass functions, are available in the GALAKSIENN library.

scholarly journals Deterministic Self-Propagating Star Formation

1989 ◽  
Vol 120 ◽  
pp. 518-523
Author(s):  
Jan Palouš
Keyword(s):  
Star Formation ◽  
Simple Model ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Galactic Evolution ◽  
Cloud Formation ◽  
Rotating Disks ◽  
Atomic Gas ◽  
High Column

AbstractThe evolution of large scale expanding structures in differentially rotating disks is studied. High column densities in some places may eventually lead to molecular cloud formation and initiate also star-formation. After some time, multi-structured arms evolve, where regions of intensive star-formation are separated from each other by regions of atomic gas or molecular clouds. This is due to the deterministic nature and to the coherence of this process. A simple model of galactic evolution is introduced and the different behaviour of Sa, Sb, and Sc galaxies is shown.

scholarly journals High-resolution LAsMA 12CO and 13CO observation of the G305 giant molecular cloud complex. I. Feedback on the molecular gas

2021 ◽  
Author(s):  
P. Mazumdar ◽  
F. Wyrowski ◽  
D. Colombo ◽  
J. S. Urquhart ◽  
M. A. Thompson ◽  
...  
Keyword(s):  
High Resolution ◽  
Molecular Cloud ◽  
Complex I ◽  
Molecular Gas ◽  
Giant Molecular Cloud ◽  
Cloud Complex

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.

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