scholarly journals Chemical evolution of galaxies: emerging dust and the different gas phases in a new multiphase code

2020 ◽  
Vol 494 (1) ◽  
pp. 146-160
Author(s):  
I Millán-Irigoyen ◽  
M Mollá ◽  
Y Ascasibar
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Molecular Gas ◽  
Multiphase Model ◽  
Milky Way Galaxy ◽  
Gas Phases ◽  
Conversion Rates ◽  
Low Metallicity ◽  
Consistent Treatment ◽  
Physical Principles

ABSTRACT Dust plays an important role in the evolution of a galaxy, as it is one of the main ingredients for efficient star formation. Dust grains are also a sink/source of metals when they are created/destroyed, and, therefore, a self-consistent treatment is key in order to correctly model chemical evolution. In this work, we discuss the implementation of dust physics in our current multiphase model, which also follows the evolution of atomic, ionized and molecular gas. Our goal is to model the conversion rates among the different phases of the interstellar medium, including the creation, growth and destruction of dust, based, as far as possible, on physical principles rather than on phenomenological recipes. We first present the updated set of differential equations and then discuss the results. We calibrate our model against observations of the Milky Way Galaxy and compare its predictions with extant data. Our results are broadly consistent with the observed data for intermediate and high metallicities, but the models tend to produce more dust than is observed in the low-metallicity regime.

scholarly journals The effects of different Type Ia SN yields on Milky Way chemical evolution

2021 ◽  
Vol 503 (3) ◽  
pp. 3216-3231
Author(s):  
Marco Palla
Keyword(s):  
Chemical Evolution ◽  
White Dwarf ◽  
Time Distribution ◽  
Milky Way ◽  
Massive Stars ◽  
Abundance Patterns ◽  
Type Ia ◽  
Low Metallicity ◽  
Explosion Mechanism ◽  
Chemical Evolution Model

ABSTRACT We study the effect of different Type Ia SN nucleosynthesis prescriptions on the Milky Way chemical evolution. To this aim, we run detailed one-infall and two-infall chemical evolution models, adopting a large compilation of yield sets corresponding to different white dwarf progenitors (near-Chandrasekar and sub-Chandrasekar) taken from the literature. We adopt a fixed delay time distribution function for Type Ia SNe, in order to avoid degeneracies in the analysis of the different nucleosynthesis channels. We also combine yields for different Type Ia SN progenitors in order to test the contribution to chemical evolution of different Type Ia SN channels. The results of the models are compared with recent LTE and NLTE observational data. We find that ‘classical’ W7 and WDD2 models produce Fe masses and [α/Fe] abundance patterns similar to more recent and physical near-Chandrasekar and sub-Chandrasekar models. For Fe-peak elements, we find that the results strongly depend either on the white dwarf explosion mechanism (deflagration-to-detonation, pure deflagration, double detonation) or on the initial white dwarf conditions (central density, explosion pattern). The comparison of chemical evolution model results with observations suggests that a combination of near-Chandrasekar and sub-Chandrasekar yields is necessary to reproduce the data of V, Cr, Mn and Ni, with different fractions depending on the adopted massive stars stellar yields. This comparison also suggests that NLTE and singly ionized abundances should be definitely preferred when dealing with most of Fe-peak elements at low metallicity.

scholarly journals A Comparison of Chemical Evolution between the Milky Way and M31 Galaxy

2006 ◽  
Vol 2 (S235) ◽  
pp. 313-313
Author(s):  
J. Yin ◽  
J.L. Hou ◽  
R.X. Chang ◽  
S. Boissier ◽  
N. Prantzos
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Milky Way ◽  
Local Group ◽  
Spiral Galaxies ◽  
Star Formation History ◽  
Milky Way Galaxy ◽  
Andromeda Galaxy ◽  
Formation History ◽  
Formation And Evolution

Andromeda galaxy (M31,NGC224) is the biggest spiral in the Local Group. By studying the star formation history(SFH) and chemical evolution of M31, and comparing with the Milky Way Galaxy, we are able to understand more about the formation and evolution of spiral galaxies.

scholarly journals Weak CS emission in an extremely metal-poor galaxy DDO 70

2020 ◽  
Vol 496 (1) ◽  
pp. L38-L42
Author(s):  
Kaiyi Du ◽  
Yong Shi ◽  
Zhi-Yu Zhang ◽  
Junzhi Wang ◽  
Yu Gao
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Signal To Noise Ratio ◽  
Formation Rate ◽  
Far Infrared ◽  
Molecular Gas ◽  
Solar Metallicity ◽  
Low Metallicity ◽  
Co Emission

ABSTRACT In most galaxies like the Milky Way, stars form in clouds of molecular gas. Unlike the CO emission that traces the bulk of molecular gas, the rotational transitions of HCN and CS molecules mainly probe the dense phase of molecular gas, which has a tight and almost linear relation with the far-infrared luminosity and star formation rate (SFR). However, it is unclear whether dense molecular gas exists at very low metallicity, and if exists, how it is related to star formation. In this work, we report ALMA observations of the CS J = 5 → 4 emission line of DDO 70, a nearby gas-rich dwarf galaxy with $\sim \!7{{\ \rm per\ cent}}$ solar metallicity. We did not detect CS emission from all regions with strong CO emission. After stacking all CS spectra from CO-bright clumps, we find no more than a marginal detection of CS J = 5 → 4 transition, at a signal-to-noise ratio of ∼3.3. This 3σ upper limit deviates from the $L^\prime _{\rm CS}$–LIR and $L^\prime _{\rm CS}$–SFR relationships found in local star-forming galaxies and dense clumps in the Milky Way, implying weaker CS emission at given infrared luminosity and SFR. We discuss the possible mechanisms that suppress CS emission at low metallicity.

scholarly journals Observational constraints on the origin of the elements

2020 ◽  
Vol 635 ◽  
pp. A38 ◽  
Author(s):  
P. Eitner ◽  
M. Bergemann ◽  
C. J. Hansen ◽  
G. Cescutti ◽  
I. R. Seitenzahl ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Globular Clusters ◽  
Local Thermodynamic Equilibrium ◽  
Galactic Chemical Evolution ◽  
Galactic Disc ◽  
Milky Way Galaxy ◽  
Halo Stars ◽  
Type Ia ◽  
Low Metallicity ◽  
Different Sources

The abundance ratios of manganese to iron in late-type stars across a wide metallicity range place tight constraints on the astrophysical production sites of Fe-group elements. In this work, we investigate the chemical evolution of Mn in the Milky Way galaxy using high-resolution spectroscopic observations of stars in the Galactic disc and halo stars, as well as a sample of globular clusters. Our analysis shows that local thermodynamic equilibrium (LTE) leads to a strong imbalance in the ionisation equilibrium of Mn I and Mn II lines. Mn I produces systematically (up to 0.6 dex) lower abundances compared to the Mn II lines. Non-LTE (NLTE) radiative transfer satisfies the ionisation equilibrium across the entire metallicity range, of −3 ≲ [Fe/H] ≲ −1, leading to consistent abundances from both ionisation stages of the element. We compare the NLTE abundances with Galactic Chemical Evolution models computed using different sources of type Ia and type II supernova (SN Ia and SN II) yields. We find that a good fit to our observations can be obtained by assuming that a significant (∼75%) fraction of SNe Ia stem from a sub-Chandrasekhar (sub-Mch) channel. While this fraction is larger than that found in earlier studies (∼50%), we note that we still require ∼25% near-Mch SNe Ia to obtain solar [Mn/Fe] at [Fe/H] = 0. Our new data also suggest higher SN II Mn yields at low metallicity than typically assumed in the literature.

scholarly journals Surveys for Metal-Poor Stars in the Galaxy: A New Window on the Low-Abundance Universe

1998 ◽  
Vol 11 (1) ◽  
pp. 58-61
Author(s):  
T.C. Beers
Keyword(s):  
Milky Way ◽  
High Signal ◽  
Signal To Noise ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
History Of ◽  
Chemical History ◽  
Low Metallicity ◽  
New Generation ◽  
The Universe

Measurement of the abundances of the light and heavy elements in stars of the Milky Way galaxy is the cornerstone for the study of numerous aspects of chemical evolution in galaxies and the Universe. We stand poised to enter an era of rapid understanding, as new-generation telescopes with apertures in the 8m-10m class enable astronomers to obtain high-resolution, high-signal-to-noise near-UV, optical, and IR spectra of the stars which have locked up the chemical history of our Galaxy in their outer atmospheres. It is thus appropriate to review present surveys for the low-metallicity stars of our Galaxy, as the stars we uncover today will be studied so intensively in the coming decades.

scholarly journals Planck’s dusty GEMS

2018 ◽  
Vol 620 ◽  
pp. A61 ◽  
Author(s):  
R. Cañameras ◽  
C. Yang ◽  
N. P. H. Nesvadba ◽  
A. Beelen ◽  
R. Kneissl ◽  
...  
Keyword(s):  
Milky Way ◽  
High Redshift ◽  
Molecular Gas ◽  
Giant Molecular Clouds ◽  
Line Energy ◽  
Star Forming ◽  
Luminous Infrared Galaxies ◽  
Gas Phases ◽  
Radiation Fields ◽  
Far Ultraviolet

We present an extensive CO emission-line survey of the Planck’s dusty Gravitationally Enhanced subMillimetre Sources, a small set of 11 strongly lensed dusty star-forming galaxies at z = 2–4 discovered with Planck and Herschel satellites, using EMIR on the IRAM 30-m telescope. We detected a total of 45 CO rotational lines from Jup = 3 to Jup = 11, and up to eight transitions per source, allowing a detailed analysis of the gas excitation and interstellar medium conditions within these extremely bright (μLFIR = 0.5 − 3.0 × 1014L⊙), vigorous starbursts. The peak of the CO spectral-line energy distributions (SLEDs) fall between Jup = 4 and Jup = 7 for nine out of 11 sources, in the same range as other lensed and unlensed submillimeter galaxies (SMGs) and the inner regions of local starbursts. We applied radiative transfer models using the large velocity gradient approach to infer the spatially-averaged molecular gas densities, nH2 ≃ 102.6 − 104.1 cm−3, and kinetic temperatures, Tk ≃ 30–1000 K. In five sources, we find evidence of two distinct gas phases with different properties and model their CO SLED with two excitation components. The warm (70–320 K) and dense gas reservoirs in these galaxies are highly excited, while the cooler (15–60 K) and more extended low-excitation components cover a range of gas densities. In two sources, the latter is associated with diffuse Milky Way-like gas phases of density nH2 ≃ 102.4 − 102.8 cm−3, which provides evidence that a significant fraction of the total gas masses of dusty starburst galaxies can be embedded in cool, low-density reservoirs. The delensed masses of the warm star-forming molecular gas range from 0.6to12 × 1010 M⊙. Finally, we show that the CO line luminosity ratios are consistent with those predicted by models of photon-dominated regions (PDRs) and disfavor scenarios of gas clouds irradiated by intense X-ray fields from active galactic nuclei. By combining CO, [C I] and [C II] line diagnostics, we obtain average PDR gas densities significantly higher than in normal star-forming galaxies at low-redshift, as well as far-ultraviolet radiation fields 102–104 times more intense than in the Milky Way. These spatially-averaged conditions are consistent with those in high-redshift SMGs and in a range of low-redshift environments, from the central regions of ultra-luminous infrared galaxies and bluer starbursts to Galactic giant molecular clouds.

scholarly journals 1.3. First stellar iron abundance measurements in the Galactic center

1998 ◽  
Vol 184 ◽  
pp. 21-22 ◽  
Author(s):  
K. Sellgren ◽  
J. S. Carr ◽  
S. C. Balachandran
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Chemical Evolution ◽  
Milky Way ◽  
Galactic Center ◽  
Star Formation History ◽  
Stellar Abundances ◽  
Milky Way Galaxy ◽  
Formation History ◽  
Iron Abundance

The disk of the Milky Way galaxy shows evidence for gas-phase abundances which increase with decreasing radius (Simpson et al. 1995; Afflerbach et al. 1997). Sustained star formation in the center of the Milky Way Galaxy may be fueled by inflow of inner disk gas (Serabyn & Morris 1996), suggesting that Galactic Center (GC) stars may be metal-rich. Measurements of stellar abundances in the GC allow us to explore the chemical evolution of our Galaxy's nucleus and to infer its star formation history.

scholarly journals The evolution of the oxygen abundance radial gradient in the Milky Way Galaxy disk

2016 ◽  
Vol 12 (S323) ◽  
pp. 245-253
Author(s):  
Mercedes Mollá ◽  
Oscar Cavichia ◽  
Roberto D. D. Costa ◽  
Walter J. Maciel ◽  
Brad Gibson ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Milky Way ◽  
Formation Rate ◽  
Milky Way Galaxy ◽  
Oxygen Abundance ◽  
Radial Gradient ◽  
Rate Laws ◽  
Galaxy Disk ◽  
Low Mass

AbstractWe review the state of our chemical evolution models for spiral and low mass galaxies. We analyze the consequences of using different stellar yields, infall rate laws and star formation prescriptions in the time/redshift evolution of the radial distributions of abundances, and other quantities as star formation rate or gas densities, in the Milky Way Galaxy; In particular we will study the evolution of the oxygen abundance radial gradient analyzing its relation with the ratio SFR/infall. We also compare the results with our old chemical evolution models, cosmological simulations and with the existing data, mainly with the planetary nebulae abundances.

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