PopRatio: A program to calculate atomic level populations in astrophysical plasmas

Silva, A. I.; Viegas, S. M.

doi:10.1016/s0010-4655(01)00149-7

Cited by 18 publications

(16 citation statements)

References 25 publications

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“…Both the heating and cooling strongly depend on the ionization fraction x e . Exact expressions adopted for the various processes can be found in: 1) Wolfire et al (1995); 2) Raga et al (1997); 3) Verner & Ferland (1996); 4) Silva & Viegas (2001 We will summarize the features of the code with an emphasis on the aspects most relevant for the present work.…”

Section: Methodsmentioning

confidence: 99%

Periodic bursts of star formation in irregular galaxies

Pelupessy

Werf

Icke

2004

A&A

108

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Abstract. We present N-body/SPH simulations of the evolution of an isolated dwarf galaxy including a detailed model for the ISM, star formation and stellar feedback. Depending on the strength of the feedback, the modelled dwarf galaxy shows periodic or quasi-periodic bursts of star formation of moderate strength. The period of the variation is related to the dynamical timescale, of the order of 1.5 × 10 8 yr. We show that the results of these simulations are in good agreement with recent detailed observations of dwarf irregulars (dIrr) and that the peculiar kinematic and morphological properties of these objects, as revealed by high resolution HI studies, are fully reproduced. We discuss these results in the context of recent surveys of dwarf galaxies and point out that if the star formation pattern of our model galaxy is typical of dwarf irregulars this could explain the scatter of observed properties of dwarf galaxies. Specifically, we show that the time-sampled distribution of the ratio between the instanteneous star formation rate (SFR) and the mean SFR is similar to the distribution in observed samples of dwarf galaxies.

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Section: Methodsmentioning

confidence: 99%

Periodic bursts of star formation in irregular galaxies

Pelupessy

Werf

Icke

2004

A&A

108

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“…where Aij is the probability of spontaneous decay , Bij is the probability of stimulated emission, uij is the energy density of the cosmic microwave background radiation field, Γij is the indirect excitation rate due to fluorescence defined by Silva & Viegas (2001). In addition, the excitation and deexcitation terms due to collisions are included.…”

Section: Deriving Physical Conditions Through C I Fine Structure Linementioning

confidence: 99%

Cold gas and a Milky Way-type 2175-Å bump in a metal-rich and highly depleted absorption system

Caucal

Noterdaeme

et al. 2015

Mon. Not. R. Astron. Soc.

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We report the detection of a strong Milky Way-type 2175Å extinction bump at z = 2.1166 in the quasar spectrum towards SDSS J121143.42+083349.7 from the Sloan Digital Sky Survey (SDSS) Data Release 10. We conduct follow up observations with the Echelle Spectrograph and Imager (ESI) onboard the Keck-II telescope and the Ultraviolet and Visual Echelle Spectrograph (UVES) on the VLT. This 2175Å absorber is remarkable in that we simultaneously detect neutral carbon (C i), neutral chlorine (Cl i), and carbon monoxide (CO). It also qualifies as a damped Lyman alpha system. The J1211+0833 absorber is found to be metal-rich and has a dust depletion pattern resembling that of the Milky Way disk clouds. We use the column densities of the C i fine structure states and the C ii/C i ratio (under the assumption of ionization equilibrium) to derive the temperature and volume density in the absorbing gas. A Cloudy photoionization model is constructed, which utilizes additional atoms/ions to constrain the physical conditions. The inferred physical conditions are consistent with a canonical cold (T ∼ 100 K) neutral medium with a high density (n(H i) ∼ 100 cm −3 ) and a slightly higher pressure than the local interstellar medium. Given the simultaneous presence of C i, CO, and the 2175Å bump, combined with the high metallicity, high dust depletion level and overall low ionization state of the gas, the absorber towards J1211+0833 supports the scenario that the presence of the bump requires an evolved stellar population.

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“…The latter radiation field is ruled out by the observations. [See the electronic edition of the Journal for a color version of this figure. ] To perform the calculation, we adopt the software packaged Popratio developed by Silva & Viegas (2001, which incorporates modern atomic data for these various ions.…”

Section: Indirect Uv Pumpingmentioning

confidence: 99%

Dissecting the Circumstellar Environment of γ‐Ray Burst Progenitors

Prochaska

Chen

Bloom

2006

ApJ

160

240

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We investigate properties of the interstellar medium ( ISM ) in galaxies hosting long-duration -ray bursts (GRBs) from an analysis of atomic species ( Mg 0 , Fe 0 ) and excited fine-structure levels of ions (e.g., Si + ). Our analysis is guided primarily by echelle observations of GRB 050730 and GRB 051111. These sight lines exhibit fine-structure transitions of O 0 , Si + , and Fe + gas that have not yet been detected in intervening quasar absorption-line systems. Our results indicate that the gas with large Mg i equivalent width (e.g., GRB 051111) must occur at distances k50 pc from GRB afterglows to avoid photoionization. We examine the mechanisms for fine-structure excitation and find that two processes can contribute: (1) indirect UV pumping by the GRB afterglow provided a far-UV intensity in excess of 10 6 times the Galactic radiation field; and (2) collisional excitation in gas with electron density n e > 10 4 cm À3 . The observed abundances of excited ions are well explained by UV pumping with the gas at r $ a few hundred pc from the afterglow for GRB 051111 and r < 100 pc for GRB 050730, without invoking extreme gas density and temperature in the ISM. We show that UV pumping alone provides a simple explanation for all reported detections of excited ions in GRB afterglow spectra. The presence of strong fine-structure transitions therefore may offer little constraint for the gas density or temperature. We discuss additional implications of UV pumping including its impact on chemical abundance measurements, new prospects for observing line-strength variability, and future prospects for studying the gas density and temperature. Finally, we list a series of criteria that can distinguish between the mechanisms of UV pumping and collisional excitation.

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PopRatio: A program to calculate atomic level populations in astrophysical plasmas

Cited by 18 publications

References 25 publications

Periodic bursts of star formation in irregular galaxies

Periodic bursts of star formation in irregular galaxies

Cold gas and a Milky Way-type 2175-Å bump in a metal-rich and highly depleted absorption system

Dissecting the Circumstellar Environment of γ‐Ray Burst Progenitors

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