scholarly journals How do different spiral arm models impact the ISM and GMC population?

2020 ◽  
Vol 498 (1) ◽  
pp. 1159-1174
Author(s):  
Alex R Pettitt ◽  
Clare L Dobbs ◽  
Junichi Baba ◽  
Dario Colombo ◽  
Ana Duarte-Cabral ◽  
...  
Keyword(s):  
Radial Dependence ◽  
Spiral Arms ◽  
Star Forming ◽  
Gas Kinematics ◽  
Cloud Properties ◽  
Grand Design ◽  
Pattern Speeds ◽  
Galactic Spiral ◽  
Spiral Model ◽  
Spiral Arm

ABSTRACT The nature of galactic spiral arms in disc galaxies remains elusive. Regardless of the spiral model, arms are expected to play a role in sculpting the star-forming interstellar medium (ISM). As such, different arm models may result in differences in the structure of the ISM and molecular cloud properties. In this study, we present simulations of galactic discs subject to spiral arm perturbations of different natures. We find very little difference in how the cloud population or gas kinematics vary between the different grand design spirals, indicating that the ISM on cloud scales cares little about where spiral arms come from. We do, however, see a difference in the interarm/arm mass spectra, and minor differences in tails of the distributions of cloud properties (as well as radial variations in the stellar/gaseous velocity dispersions). These features can be attributed to differences in the radial dependence of the pattern speeds between the different spiral models, and could act as a metric of the nature of spiral structure in observational studies.

scholarly journals Spiral morphology in an intensely star-forming disk galaxy more than 12 billion years ago

Science ◽  
2021 ◽  
pp. eabe9680
Author(s):  
Takafumi Tsukui ◽  
Satoru Iguchi
Keyword(s):  
Big Bang ◽  
Compact Structure ◽  
Spiral Arms ◽  
Star Forming ◽  
Gas Kinematics ◽  
Internal Structures ◽  
The Galaxy ◽  
Galaxy Center ◽  
The Big Bang ◽  
Tidal Tails

Spiral galaxies have distinct internal structures including a stellar bulge, disk and spiral arms. It is unknown when in cosmic history these structures formed. We analyze observations of BRI 1335–0417, an intensely star-forming galaxy in the distant Universe, at redshift 4.41. The [C ii] gas kinematics show a steep velocity rise near the galaxy center and have a two-armed spiral morphology, which extends from about 2 to 5 kiloparsecs in radius. We interpret these features as due to a central compact structure, such as a bulge; a rotating gas disk; and either spiral arms or tidal tails. These features had formed within 1.4 billion years after the Big Bang, long before the peak of cosmic star formation.

scholarly journals Galactic spiral structure

2009 ◽  
Vol 465 (2111) ◽  
pp. 3425-3446 ◽  
Author(s):  
Charles Francis ◽  
Erik Anderson
Keyword(s):  
Pitch Angle ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Stellar Orbits ◽  
Grand Design ◽  
Galactic Spiral Structure ◽  
Pattern Speed ◽  
Galactic Spiral ◽  
Almost All ◽  
Spiral Arm

We describe the structure and composition of six major stellar streams in a population of 20 574 local stars in the New Hipparcos Reduction with known radial velocities. We find that, once fast moving stars are excluded, almost all stars belong to one of these streams. The results of our investigation have led us to re-examine the hydrogen maps of the Milky Way, from which we identify the possibility of a symmetric two-armed spiral with half the conventionally accepted pitch angle. We describe a model of spiral arm motions that matches the observed velocities and compositions of the six major streams, as well as the observed velocities of the Hyades and Praesepe clusters at the extreme of the Hyades stream. We model stellar orbits as perturbed ellipses aligned at a focus in coordinates rotating at the rate of precession of apocentre. Stars join a spiral arm just before apocentre, follow the arm for more than half an orbit, and leave the arm soon after pericentre. Spiral pattern speed equals the mean rate of precession of apocentre. Spiral arms are shown to be stable configurations of stellar orbits, up to the formation of a bar and/or ring. Pitch angle is directly related to the distribution of orbital eccentricities in a given spiral galaxy. We show how spiral galaxies can evolve to form bars and rings. We show that orbits of gas clouds are stable only in bisymmetric spirals. We conclude that spiral galaxies evolve toward grand design two-armed spirals. We infer from the velocity distributions that the Milky Way evolved into this form about 9 billion years ago (Ga).

scholarly journals Substructure within galactic spiral arms as derived from studies at 21 cm

1959 ◽  
Vol 9 ◽  
pp. 355-359
Author(s):  
R. D. Davies
Keyword(s):  
Fine Structure ◽  
High Resolution ◽  
Velocity Dispersion ◽  
Detailed Structure ◽  
Hydrogen Line ◽  
Spiral Arms ◽  
Frequency Structure ◽  
Galactic Spiral ◽  
Spiral Arm

Detailed structure within the spiral arms of our Galaxy is suggested by hydrogen-line spectra taken with high resolution in frequency [1]. The spectra show much detail in each maximum (spiral arm). It is not clear, however, if this frequency structure refers to fine structure in depth or in velocity dispersion or in both. Fine structure in position and depth has been inferred from 21-cm drift curves taken across the nearby spiral arms. The results of three investigations will be discussed. Two have been published in some detail [2, 3] and will only be summarized here.

scholarly journals Gas kinematics in high-mass star-forming regions from the Perseus spiral arm

2017 ◽  
Vol 61 (9) ◽  
pp. 760-774 ◽  
Author(s):  
M. S. Kirsanova ◽  
A. M. Sobolev ◽  
M. Thomasson
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Gas Kinematics ◽  
Star Forming Regions ◽  
Spiral Arm

scholarly journals An Updated View of Giant Molecular Clouds, Gas Flows and Star Formation in M51 with PAWS

2012 ◽  
Vol 8 (S292) ◽  
pp. 139-142
Author(s):  
S. E. Meidt ◽  
E. Schinnerer ◽  
A. Hughes ◽  
D. Colombo ◽  
J. Pety ◽  
...  
Keyword(s):  
Star Formation ◽  
External Pressure ◽  
Radial Dependence ◽  
Gas Flows ◽  
Giant Molecular Clouds ◽  
Global Pattern ◽  
Grand Design ◽  
Co Emission ◽  
Spiral Arm

AbstractWe present an overview of the latest results from the PdBI Arcsecond Whirlpool Survey (PAWS, PI: E. Schinnerer), which has mapped CO(1-0) emission in the nearby grand-design spiral galaxy M51 at 40pc resolution. Our data are sensitive to GMCs above 105 M⊙, allowing the construction of the largest GMC catalog to date – containing over 1500 objects – using the CPROPS algorithm (Rosolowsky & Leroy 2006). In the inner disk of M51, the properties of the CO emission show significant variation that can be linked to the dynamical environment in which the molecular gas is located. We find that dynamically distinct regions host clouds with different properties and exhibit different GMC mass spectra, as well as distinct patterns of star formation. To understand how this sensitivity to environment emerges, we consider the role of pressure on GMC stabilization (including shear and star formation feedback-driven turbulence). We suggest that, in the presence of significant external pressure, streaming motions driven by the spiral arm can act to reduce the surface pressure on clouds. The resulting stabilization impacts the global pattern of star formation and can account for the observed non-monotonic radial dependence of the gas depletion time. Our findings have implications for the observed scatter in the standard GMC relations and extragalactic star formation laws.

scholarly journals Spatial and velocity offsets of Galactic masers from the centres of spiral arms

2019 ◽  
Vol 489 (2) ◽  
pp. 2819-2829 ◽  
Author(s):  
Jacques P Vallée
Keyword(s):  
Star Formation ◽  
Pitch Angle ◽  
Milky Way ◽  
Galactic Centre ◽  
Spiral Arms ◽  
Corotation Radius ◽  
Pattern Speed ◽  
Spiral Model ◽  
Spiral Arm ◽  
Co Gas

ABSTRACT Some theories about the spiral arms of galaxies predict an offset between different tracers of star formation. Our goal in this paper is to find such an offset between the observed locations of radio masers and the locations of the arms, using a recent four-arm model fitted to the CO 1–0 gas. Our method is to compare a recent global four-arm spiral model (as fitted to the arms’ tangents in the observed broad CO 1–0 gas) with the recent results for the trigonometric distances of radio masers, for the main arms (Cygnus–Norma, Perseus, Sagittarius–Carina, Scutum and Norma). Our results indicate that most radio masers are near the inner edge of each spiral arm (towards the Galactic Centre). These masers are offset from the model arm (where the broad CO 1–0 molecular region resides), by 0.34 ± 0.06 kpc inward. In radial velocity space, the median offset between masers and the CO-fitted model is around 10 ± 1 km s–1. Based on the fact that the masers are observed here to be radially inward of the broad CO gas in the Cygnus arm at 15 kpc along the Galactic meridian, the corotation radius of the Milky Way disc is >15 kpc distant from the Galactic Centre and the density wave’s angular pattern speed is <15 km s–1 kpc–1. The pitch angle of the arm should be measured using many arm tracers, and located on both sides of the Galactic meridian, to ensure better precision and to avoid a bias pertinent to a single tracer.

Spiral arm amplitude variations and pattern speeds in the grand design galaxies M51, M81, and M100

1989 ◽  
Vol 343 ◽  
pp. 602 ◽  
Author(s):  
Bruce G. Elmegreen ◽  
Philip E. Seiden ◽  
Debra Meloy Elmegreen
Keyword(s):  
Grand Design ◽  
Pattern Speeds ◽  
Spiral Arm

scholarly journals Binary Wolf-Rayet Stars

1989 ◽  
Vol 8 ◽  
pp. 153-154
Author(s):  
B. Hidayat ◽  
K. A. van der Hucht
Keyword(s):  
Magnetic Field ◽  
Galactocentric Distance ◽  
Spiral Arms ◽  
Limited Volume ◽  
Galactic Spiral ◽  
Spiral Arm

AbstractThe distribution of the WR cluster members is interpreted in terms of their association with the galactic spiral-arm pattern. It is suggested that in a limited volume the number fraction of WR binaries is influenced more by magnetic field properties of the spiral arms, than by function of the galactocentric distance.

Cold gas studies of a z = 2.5 protocluster

2020 ◽  
Vol 15 (S359) ◽  
pp. 136-140
Author(s):  
Minju M. Lee ◽  
Ichi Tanaka ◽  
Rohei Kawabe
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Kinematic Model ◽  
Molecular Gas ◽  
General View ◽  
Massive Galaxies ◽  
Star Forming ◽  
Gas Kinematics ◽  
Narrow Band Filter ◽  
Stellar Masses

AbstractWe present studies of a protocluster at z =2.5, an overdense region found close to a radio galaxy, 4C 23.56, using ALMA. We observed 1.1 mm continuum, two CO lines (CO (4–3) and CO (3–2)) and the lower atomic carbon line transition ([CI](3P1-3P0)) at a few kpc (0″.3-0″.9) resolution. The primary targets are 25 star-forming galaxies selected as Hα emitters (HAEs) that are identified with a narrow band filter. These are massive galaxies with stellar masses of > 1010Mʘ that are mostly on the galaxy main sequence at z =2.5. We measure the molecular gas mass from the independent gas tracers of 1.1 mm, CO (3–2) and [CI], and investigate the gas kinematics of galaxies from CO (4–3). Molecular gas masses from the different measurements are consistent with each other for detection, with a gas fraction (fgas = Mgas/(Mgas+ Mstar)) of ≃ 0.5 on average but with a caveat. On the other hand, the CO line widths of the protocluster galaxies are typically broader by ˜50% compared to field galaxies, which can be attributed to more frequent, unresolved gas-rich mergers and/or smaller sizes than field galaxies, supported by our high-resolution images and a kinematic model fit of one of the galaxies. We discuss the expected scenario of galaxy evolution in protoclusters at high redshift but future large surveys are needed to get a more general view.

scholarly journals Birth sites of young stellar associations and recent star formation in a flocculent corrugated disc

2020 ◽  
Vol 499 (4) ◽  
pp. 5623-5640
Author(s):  
Alice C Quillen ◽  
Alex R Pettitt ◽  
Sukanya Chakrabarti ◽  
Yifan Zhang ◽  
Jonathan Gagné ◽  
...  
Keyword(s):  
Space Distribution ◽  
Solar Neighbourhood ◽  
Low Velocity ◽  
Stellar Association ◽  
Stellar Orbits ◽  
Pattern Speeds ◽  
Moving Groups ◽  
Orbit Integration ◽  
Stellar Associations ◽  
Spiral Arm

ABSTRACT With backwards orbit integration, we estimate birth locations of young stellar associations and moving groups identified in the solar neighbourhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at a smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule are the Argus and Octans associations, which formed outside the Sun’s galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a filamentary and corrugated disc of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the radial/tangential (UV) stellar velocity distribution for stars in the solar neighbourhood. This would be expected if they were born in a spiral arm, which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase-space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low-velocity dispersion disc stars.

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