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 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 Induced Star Formation in M17: High Resolution NH3 and IR Observations

1987 ◽  
Vol 115 ◽  
pp. 141-142
Author(s):  
M. Felli ◽  
M. Massi ◽  
R. Stanga ◽  
E. Churchwell
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Type Structure ◽  
Radio Continuum ◽  
Ionization Front ◽  
The South ◽  
The West ◽  
H Ii Region ◽  
Linear Diameter

A VLA radio continuum study of the H II region M17 (Felli, Churchwell and Massi, 1984) has shown the presence of an elongated sharp arc structure in the South Bar of the nebula, in a region of heavy obscuration. The arc has been interpreted as an ionization boundary, viewed edge on, located between the diffuse H II region, to the east, and a dense component of the extended molecular cloud, to the west. About 3″ to the west of this arc, an ultra-compact H II region has been found. This has a shell type structure, a linear diameter of 0.004 pc and probably is the result of induced star formation in the molecular cloud produced by the pressure front preceding the ionization front.

scholarly journals How does metallicity affect the gas and dust properties of galaxies?

2015 ◽  
Vol 11 (S315) ◽  
pp. 191-198 ◽  
Author(s):  
Suzanne C. Madden ◽  
Diane Cormier ◽  
Aurélie Rémy-Ruyer
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Dwarf Galaxies ◽  
Molecular Gas ◽  
Ionized Gas ◽  
Active Star ◽  
Multiphase Structure ◽  
Wide Range ◽  
Self Consistent ◽  
Low Metallicity

AbstractComparison of the ISM properties of a wide range of metal poor galaxies with normal metal-rich galaxies reveals striking differences. We find that the combination of the low dust abundance and the active star formation results in a very porous ISM filled with hard photons, heating the dust in dwarf galaxies to overall higher temperatures than their metal-rich counterparts. This results in photodissociation of molecular clouds to greater depths, leaving relatively large PDR envelopes and difficult-to-detect CO cores. From detailed modeling of the low-metallicity ISM, we find significant fractions of CO-dark H2 - a reservoir of molecular gas not traced by CO, but present in the [CII] and [CI]-emitting envelopes. Self-consistent analyses of the neutral and ionized gas diagnostics along with the dust SED is the necessary way forward in uncovering the multiphase structure of galaxies.

scholarly journals The enigmatic loop III and the Local Galactic Structure

2006 ◽  
Vol 2 (S237) ◽  
pp. 119-123 ◽  
Author(s):  
M. Kun
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Galactic Structure ◽  
Radio Continuum ◽  
Local Bubble ◽  
Preliminary Results ◽  
Continuum Structure

AbstractThe aim of the present study, based on literature data, is to find signatures of the giant radio continuum structure Loop III on the nearby interstellar medium, and search for molecular cloud and star formation, possibly triggered by its expansion. The preliminary results are as follows: (1) The 3D map of the Local Bubble, published by Lallement et al. (2003) suggests that Loop III is probably more distant than the early models had indicated. (2) The molecular clouds at high galactic latitudes in the 2nd Galactic quadrant are probably associated with the neutral/molecular wall of Loop III. (3) Star formation in Lynds 1333 and Lynds 1082 (GF 9) might have been triggered by the expansion of Loop III. (4) The supernova(e), whose explosion produced Loop III, might have been located in the SU Cas association.

scholarly journals Molecular gas kinematics of the CMZ: Great oaks from little acorns grow

2016 ◽  
Vol 11 (S322) ◽  
pp. 85-89
Author(s):  
Jonathan D. Henshaw
Keyword(s):  
Star Formation ◽  
Velocity Field ◽  
Molecular Clouds ◽  
Extreme Environment ◽  
Galactic Centre ◽  
Molecular Gas ◽  
Evolutionary Sequence ◽  
Gas Kinematics ◽  
Gravitational Instabilities ◽  
The Galaxy

AbstractThe central molecular zone (CMZ) hosts some of the most massive and dense molecular clouds and star clusters in the Galaxy, offering an important window into star formation under extreme conditions. Star formation in this extreme environment may be closely linked to the 3-D distribution and orbital dynamics of the gas. Here I discuss how our new, accurate description of the {l,b,v} structure of the CMZ is helping to constrain its 3-D geometry. I also present the discovery of a highly-regular, corrugated velocity field located just upstream from the dust ridge molecular clouds (which include G0.253+0.016 and Sgr B2). The extremes in this velocity field correlate with a series of massive (~ 104 M⊙) cloud condensations. The corrugation wavelength (~23 pc) and cloud separation (~8 pc) closely agree with the predicted Toomre (~17 pc) and Jeans (~6 pc) lengths, respectively. I conclude that gravitational instabilities are driving the formation of molecular clouds within the Galactic Centre gas stream. Furthermore, I suggest that these seeds are the historical analogues of the dust ridge molecular clouds – possible progenitors of some of the most massive and dense molecular clouds in the Galaxy. If our current best understanding for the 3-D geometry of this system is confirmed, these clouds may pinpoint the beginning of an evolutionary sequence that can be followed, in time, from cloud condensation to star formation.

From global to local scales in galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 391-395
Author(s):  
Sebastian F. Sánchez ◽  
Carlos Lopez Cobá
Keyword(s):  
Star Formation ◽  
Spatial Scales ◽  
Bimodal Distribution ◽  
Spectroscopic Properties ◽  
Molecular Gas ◽  
Ionized Gas ◽  
Galaxy Surveys ◽  
Quenching Process ◽  
Formation Efficiency ◽  
Integral Field

AbstractWe summarize here some of the results reviewed recently by Sanchez (2020) comprising the advances in the comprehension of galaxies in the nearby universe based on integral field spectroscopic galaxy surveys. In particular we explore the bimodal distribution of galaxies in terms of the properties of their ionized gas, showing the connection between the star-formation (quenching) process with the presence (absence) of molecular gas and the star-formation efficiency. We show two galaxy examples that illustrates the well known fact that ionization in galaxies (and the processes that produce it), does not happen monolitically at galactic scales. This highlight the importance to explore the spectroscopic properties of galaxies and the evolutionary processes unveiled by them at different spatial scales, from sub-kpc to galaxy wide.

scholarly journals Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA

2019 ◽  
Vol 488 (3) ◽  
pp. 3904-3928 ◽  
Author(s):  
Ryan Leaman ◽  
Francesca Fragkoudi ◽  
Miguel Querejeta ◽  
Gigi Y C Leung ◽  
Dimitri A Gadotti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Mechanical Energy ◽  
Molecular Gas ◽  
Ionized Gas ◽  
Star Forming ◽  
Stellar Feedback ◽  
Dominant Component ◽  
The Galaxy ◽  
Field Lines

ABSTRACT Stellar feedback plays a significant role in modulating star formation, redistributing metals, and shaping the baryonic and dark structure of galaxies – however, the efficiency of its energy deposition to the interstellar medium is challenging to constrain observationally. Here we leverage HST and ALMA imaging of a molecular gas and dust shell ($M_{\mathrm{ H}_2} \sim 2\times 10^{5}\, {\rm M}_{\odot }$) in an outflow from the nuclear star-forming ring of the galaxy NGC 3351, to serve as a boundary condition for a dynamical and energetic analysis of the outflowing ionized gas seen in our MUSE TIMER survey. We use starburst99 models and prescriptions for feedback from simulations to demonstrate that the observed star formation energetics can reproduce the ionized and molecular gas dynamics – provided a dominant component of the momentum injection comes from direct photon pressure from young stars, on top of supernovae, photoionization heating, and stellar winds. The mechanical energy budget from these sources is comparable to low luminosity active galactic neuclei, suggesting that stellar feedback can be a relevant driver of bulk gas motions in galaxy centres – although here ≲10−3 of the ionized gas mass is escaping the galaxy. We test several scenarios for the survival/formation of the cold gas in the outflow, including in situ condensation and cooling. Interestingly, the geometry of the molecular gas shell, observed magnetic field strengths and emission line diagnostics are consistent with a scenario where magnetic field lines aided survival of the dusty ISM as it was initially launched (with mass-loading factor ≲1) from the ring by stellar feedback. This system’s unique feedback-driven morphology can hopefully serve as a useful litmus test for feedback prescriptions in magnetohydrodynamical galaxy simulations.

scholarly journals The supergiant shell with triggered star formation in the dwarf irregular galaxy IC 2574: neutral and ionized gas kinematics

2014 ◽  
Vol 444 (1) ◽  
pp. 376-391 ◽  
Author(s):  
O. V. Egorov ◽  
T. A. Lozinskaya ◽  
A. V. Moiseev ◽  
G. V. Smirnov-Pinchukov
Keyword(s):  
Star Formation ◽  
Irregular Galaxy ◽  
Ionized Gas ◽  
Gas Kinematics

scholarly journals The global star formation law: from dense cores to extreme starbursts

2006 ◽  
Vol 2 (S237) ◽  
pp. 331-335
Author(s):  
Yu Gao
Keyword(s):  
Star Formation ◽  
Linear Correlation ◽  
Molecular Clouds ◽  
High Redshift ◽  
Gas Content ◽  
Molecular Gas ◽  
Giant Molecular Clouds ◽  
Active Star ◽  
Dense Cores ◽  
The Galaxy

AbstractActive star formation (SF) is tightly related to the dense molecular gas in the giant molecular clouds' dense cores. Our HCN (measure of the dense molecular gas) survey in 65 galaxies (including 10 ultraluminous galaxies) reveals a tight linear correlation between HCN and IR (SF rate) luminosities, whereas the correlation between IR and CO (measure of the total molecular gas) luminosities is nonlinear. This suggests that the global SF rate depends more intimately upon the amount of dense molecular gas than the total molecular gas content. This linear relationship extends to both the dense cores in the Galaxy and the hyperluminous extreme starbursts at high-redshift. Therefore, the global SF law in dense gas appears to be linear all the way from dense cores to extreme starbursts, spanning over nine orders of magnitude in IR luminosity.

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