The effect of spiral arms on star formation in the Galaxy

AbstractWe present VLA 21-cm observations of the spiral galaxy ESO 481-G017 to determine the nature of remote star formation traced by an Hii region found 43 kpc and ∼800 km s−1 from the galaxy center (in projection). ESO 481-G017 is found to have a 120 kpc Hi disk with a mass of 1.2 × 1010M⊙ and UV GALEX images reveal spiral arms extending into the gaseous disk. Two dwarf galaxies with Hi masses close to 108M⊙ are detected at distances of ∼200 kpc from ESO 481-G017 and a Hi cloud with a mass of 6 × 107M⊙ is found near the position and velocity of the remote Hii region. The Hii region is somewhat offset from the Hi cloud spatially and there is no link to ESO 481-G017 or the dwarf galaxies. We consider several scenarios for the origin of the cloud and Hii region and find the most likely is a dwarf galaxy that is undergoing ram pressure stripping. The Hi mass of the cloud and Hi luminosity of the Hii region (1038.1 erg s−1) are consistent with dwarf galaxy properties, and the stripping can trigger the star formation as well as push the gas away from the stars.

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Zoom-in cosmological hydrodynamical simulation of a star-forming barred, spiral galaxy at redshift z = 2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2065 ◽

2019 ◽

Vol 488 (4) ◽

pp. 4674-4689 ◽

Cited By ~ 5

Author(s):

Fiorenzo Vincenzo ◽

Chiaki Kobayashi ◽

Tiantian Yuan

Keyword(s):

Star Formation ◽

Angular Velocity ◽

Spiral Galaxy ◽

Stellar Populations ◽

Spiral Arms ◽

Star Forming ◽

Thin Disc ◽

The Galaxy ◽

Barred Spiral Galaxy ◽

Zoom In

ABSTRACTWe present gas and stellar kinematics of a high-resolution zoom-in cosmological chemodynamical simulation, which fortuitously captures the formation and evolution of a star-forming barred spiral galaxy, from redshift z ∼ 3 to z ∼ 2 at the peak of the cosmic star formation rate. The galaxy disc grows by accreting gas and substructures from the environment. The spiral pattern becomes fully organized when the gas settles from a thick (with vertical dispersion σv > 50 km s−1) to a thin (σv ∼ 25 km s−1) disc component in less than 1 Gyr. Our simulated disc galaxy also has a central X-shaped bar, the seed of which formed by the assembly of dense gas-rich clumps by z ∼ 3. The star formation activity in the galaxy mainly happens in the bulge and in several clumps along the spiral arms at all redshifts, with the clumps increasing in number and size as the simulation approaches z = 2. We find that stellar populations with decreasing age are concentrated towards lower galactic latitudes, being more supported by rotation, and having also lower velocity dispersion; furthermore, the stellar populations on the thin disc are the youngest and have the highest average metallicities. The pattern of the spiral arms rotates like a solid body with a constant angular velocity as a function of radius, which is much lower than the angular velocity of the stars and gas on the thin disc; moreover, the angular velocity of the spiral arms steadily increases as a function of time, always keeping its radial profile constant. The origin of our spiral arms is also discussed.

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Spatial and Kinematic Clustering of Stars in the Galactic Disk

The Astrophysical Journal ◽

10.3847/1538-4357/abfe5d ◽

2021 ◽

Vol 922 (1) ◽

pp. 49

Author(s):

Harshil Kamdar ◽

Charlie Conroy ◽

Yuan-Sen Ting ◽

Kareem El-Badry

Keyword(s):

Star Formation ◽

Galactic Disk ◽

Spatial Scales ◽

Giant Molecular Clouds ◽

Spiral Arms ◽

Realistic Potential ◽

The Galaxy ◽

Point Correlation ◽

Power Law Index ◽

Gaia Dr2

Abstract The Galactic disk is expected to be spatially and kinematically clustered on many scales due to both star formation and the Galactic potential. In this work we calculate the spatial and kinematic two-point correlation functions (TPCF) using a sample of 1.7 × 106 stars with radial velocities from Gaia DR2. Clustering is detected on spatial scales of 1–300 pc and a velocity scale of 15 km s−1. After removing bound structures, the data have a power-law index of γ ≈ −1 for 1 pc < Δr < 100 pc and γ ≲ −1.5 for Δr > 100 pc. We interpret these results with the aid of a star-by-star simulation of the Galaxy, in which stars are born in clusters orbiting in a realistic potential that includes spiral arms, a bar, and giant molecular clouds. We find that the simulation largely agrees with the observations at most spatial and kinematic scales. In detail, the TPCF in the simulation is shallower than the data at ≲20 pc scales, and steeper than the data at ≳30 pc. We also find a persistent clustering signal in the kinematic TPCF for the data at large Δv (>5 km s−1) that is not present in the simulations. We speculate that this mismatch between observations and simulations may be due to two processes: hierarchical star formation and transient spiral arms. We also predict that the addition of ages and metallicities measured with a precision of 50% and 0.05 dex, respectively, will enhance the clustering signal beyond current measurements.

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

Science ◽

10.1126/science.abe9680 ◽

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.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1844 ◽

2019 ◽

Vol 488 (3) ◽

pp. 3904-3928 ◽

Cited By ~ 6

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.

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Astrophysical MHD turbulence: confluence of observations, simulations, and theory

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313002718 ◽

2012 ◽

Vol 8 (S294) ◽

pp. 325-336 ◽

Cited By ~ 1

Author(s):

Blakesley Burkhart ◽

Alex Lazarian

Keyword(s):

Star Formation ◽

Interstellar Medium ◽

Magnetic Reconnection ◽

Particle Transport ◽

Recent Progress ◽

Critical Component ◽

Dynamo Theory ◽

Mhd Turbulence ◽

The Galaxy

AbstractMagnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the ISM. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be imployed. In these proceedings we review recent progress that has been made on the connections between theoretical, numerical, and observational understanding of MHD turbulence as it applies to both the neutral and ionized interstellar medium.

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Pushing back the limits: detailed properties of dwarf galaxies in a ΛCDM universe

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832669 ◽

2018 ◽

Vol 616 ◽

pp. A96 ◽

Cited By ~ 26

Author(s):

Yves Revaz ◽

Pascale Jablonka

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxies ◽

Mass Scale ◽

Dwarf Spheroidal Galaxies ◽

The Galaxy ◽

Dynamical Simulations ◽

Ursa Minor ◽

Stellar Properties ◽

Star Formation Histories

We present the results of a set of high-resolution chemo-dynamical simulations of dwarf galaxies in a ΛCDM cosmology. Out of an original (3.4 Mpc/h)3 cosmological box, a sample of 27 systems are re-simulated from z = 70 to z = 0 using a zoom-in technique. Gas and stellar properties are confronted to the observations in the greatest details: in addition to the galaxy global properties, we investigated the model galaxy velocity dispersion profiles, half-light radii, star formation histories, stellar metallicity distributions, and [Mg/Fe] abundance ratios. The formation and sustainability of the metallicity gradients and kinematically distinct stellar populations are also tackled. We show how the properties of six Local Group dwarf galaxies, NGC 6622, Andromeda II, Sculptor, Sextans, Ursa Minor and Draco are reproduced, and how they pertain to three main galaxy build-up modes. Our results indicate that the interaction with a massive central galaxy could be needed for a handful of Local Group dwarf spheroidal galaxies only, the vast majority of the systems and their variety of star formation histories arising naturally from a ΛCDM framework. We find that models fitting well the local Group dwarf galaxies are embedded in dark haloes of mass between 5 × 108 to a few 109 M⊙, without any missing satellite problem. We confirm the failure of the abundance matching approach at the mass scale of dwarf galaxies. Some of the observed faint however gas-rich galaxies with residual star formation, such as Leo T and Leo P, remain challenging. They point out the need of a better understanding of the UV-background heating.

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Cosmological simulations of low-mass galaxies: some potential issues

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311000883 ◽

2010 ◽

Vol 6 (S270) ◽

pp. 503-506

Author(s):

Pedro Colín ◽

Vladimir Avila-Reese ◽

Octavio Valenzuela

Keyword(s):

Star Formation ◽

Adaptive Mesh Refinement ◽

Mass Fraction ◽

Star Formation Rate ◽

Formation Rate ◽

Mesh Refinement ◽

Adaptive Mesh ◽

Stellar Mass ◽

The Galaxy ◽

Low Mass

AbstractCosmological Adaptive Mesh Refinement simulations are used to study the specific star formation rate (sSFR=SSF/Ms) history and the stellar mass fraction, fs=Ms/MT, of small galaxies, total masses MT between few × 1010 M⊙ to few ×1011 M⊙. Our results are compared with recent observational inferences that show the so-called “downsizing in sSFR” phenomenon: the less massive the galaxy, the higher on average is its sSFR, a trend seen at least since z ~ 1. The simulations are not able to reproduce this phenomenon, in particular the high inferred values of sSFR, as well as the low values of fs constrained from observations. The effects of resolution and sub-grid physics on the SFR and fs of galaxies are discussed.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307001688 ◽

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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Planck’s dusty GEMS

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833679 ◽

2018 ◽

Vol 620 ◽

pp. A60 ◽

Cited By ~ 6

Author(s):

R. Cañameras ◽

N. P. H. Nesvadba ◽

M. Limousin ◽

H. Dole ◽

R. Kneissl ◽

...

Keyword(s):

Star Formation ◽

Near Infrared ◽

Infrared Imaging ◽

High Redshift ◽

Dust Emission ◽

Galaxy Cluster ◽

Star Forming ◽

The Galaxy ◽

Mass Outflow ◽

Gas Accretion

We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few 109 M⊙, in the strongly gravitationally lensed submillimeter galaxy “the Emerald” (PLCK_G165.7+49.0) at z = 2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5″ and 21″ formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z = 0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4–3) line and 850 μm dust emission to characterize the foreground lensing mass distribution, construct a lens model with LENSTOOL, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a 9 × 1010 M⊙, fragmented disk with 20% gas fraction. The stellar continuum morphology is much smoother and also well resolved perpendicular to the magnification axis. One of the clumps shows a pronounced blue wing in the CO(4–3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of –200 km s−1 is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.

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