scholarly journals An overview of the PAHTAT toolbox

2013 ◽  
Vol 9 (S303) ◽  
pp. 208-210
Author(s):  
P. Pilleri ◽  
C. Joblin ◽  
O. Berné ◽  
J. Montillaud ◽  
Y. Okada
Keyword(s):  
Physical Properties ◽  
Ir Spectra ◽  
Radiation Field ◽  
Uv Radiation ◽  
Column Density ◽  
Line Of Sight ◽  
Mid Infrared ◽  
Physical Conditions ◽  
Ionization Parameter

AbstractIn this contribution, we briefly describe how an observed mid-infrared (5.5-14 μm) spectrum can be used to trace key physical conditions along a given line of sight, such as the UV radiation field, the ionization parameter and the dust column density. These parameters are often difficult to determine independently from PDR models. The PAHTAT toolbox offers the opportunity to analyze mid-IR spectra using a limited number of parameters, that are associated with the physical properties of the dust and gas being observed.

scholarly journals Models of irradiated molecular shocks

2019 ◽  
Vol 622 ◽  
pp. A100 ◽  
Author(s):  
B. Godard ◽  
G. Pineau des Forêts ◽  
P. Lesaffre ◽  
A. Lehmann ◽  
A. Gusdorf ◽  
...  
Keyword(s):  
Radiation Field ◽  
Uv Radiation ◽  
Mechanical Energy ◽  
Line Emission ◽  
Low Velocity ◽  
Integration Algorithm ◽  
Physical Conditions ◽  
Wide Range ◽  
Interstellar Shocks ◽  
Molecular Lines

Context. The recent discovery of excited molecules in starburst galaxies observed with ALMA and the Herschel space telescope has highlighted the necessity to understand the relative contributions of radiative and mechanical energies in the formation of molecular lines and explore the conundrum of turbulent gas bred in the wake of galactic outflows. Aims. The goal of the paper is to present a detailed study of the propagation of low velocity (5–25 km s−1) stationary molecular shocks in environments illuminated by an external ultraviolet (UV) radiation field. In particular, we intend to show how the structure, dynamics, energetics, and chemical properties of shocks are modified by UV photons and to estimate how efficiently shocks can produce line emission. Methods. We implemented several key physico-chemical processes in the Paris-Durham shock code to improve the treatment of the radiative transfer and its impact on dust and gas particles. We propose a new integration algorithm to find the steady-state solutions of magnetohydrodynamics equations in a range of parameters in which the fluid evolves from a supersonic to a subsonic regime. We explored the resulting code over a wide range of physical conditions, which encompass diffuse interstellar clouds and hot and dense photon-dominated regions. Results. We find that C-type shock conditions cease to exist as soon as G0 > 0.2 (nH/cm−3)1/2. Such conditions trigger the emergence of another category of stationary solutions, called C*-type and CJ-type shocks, in which the shocked gas is momentarily subsonic along its trajectory. These solutions are shown to be unique for a given set of physical conditions and correspond to dissipative structures in which the gas is heated up to temperatures comprised between those found in C-type and adiabatic J-type shocks. High temperatures combined with the ambient UV field favour the production or excitation of a few molecular species to the detriment of others, hence leading to specific spectroscopic tracers such as rovibrational lines of H2 and rotational lines of CH+. Unexpectedly, the rotational lines of CH+ may carry as much as several percent of the shock kinetic energy. Conclusions. Ultraviolet photons are found to strongly modify the way the mechanical energy of interstellar shocks is processed and radiated away. In spite of what intuition dictates, a strong external UV radiation field boosts the efficiency of low velocity interstellar shocks in the production of several molecular lines which become evident tracers of turbulent dissipation.

scholarly journals The VIMOS Ultra Deep Survey: Nature, ISM properties, and ionizing spectra of CIII]λ1909 emitters at z = 2–4

2018 ◽  
Vol 612 ◽  
pp. A94 ◽  
Author(s):  
K. Nakajima ◽  
D. Schaerer ◽  
O. Le Fèvre ◽  
R. Amorín ◽  
M. Talia ◽  
...  
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
Radiation Field ◽  
High Redshift ◽  
Star Forming ◽  
Uv Emission ◽  
Distant Galaxies ◽  
Deep Survey ◽  
Ionization Parameter ◽  
Large Grid

Context. Ultraviolet (UV) emission-line spectra are used to spectroscopically confirm high-z galaxies and increasingly also to determine their physical properties. Aims. We construct photoionization models to interpret the observed UV spectra of distant galaxies in terms of the dominant radiation field and the physical condition of the interstellar medium (ISM). These models are applied to new spectroscopic observations from the VIMOS Ultra Deep Survey (VUDS). Methods. We construct a large grid of photoionization models, which use several incident radiation fields (stellar populations, active galactic nuclei (AGNs), mix of stars and AGNs, blackbodies, and others), and cover a wide range of metallicities and ionization parameters. From these models we derive new spectral UV line diagnostics using equivalent widths (EWs) of [CIII]λ1909 doublet, CIVλ1549 doublet and the line ratios of [CIII], CIV, and He IIλ1640 recombination lines. We apply these diagnostics to a sample of 450 [CIII]-emitting galaxies at redshifts z = 2–4 previously identified in VUDS. Results. We demonstrate that our photoionization models successfully reproduce observations of nearby and high-redshift sources with known radiation field and/or metallicity. For star-forming galaxies our models predict that [CIII] EW peaks at sub-solar metallicities, whereas CIV EW peaks at even lower metallicity. Using the UV diagnostics, we show that the average star-forming galaxy (EW([CIII]) ~ 2 Å) based on the composite of the 450 UV-selected galaxies’ spectra The inferred metallicity and ionization parameter is typically Z = 0.3–0.5 Z⊙ and logU = −2.7 to − 3, in agreement with earlier works at similar redshifts. The models also indicate an average age of 50–200 Myr since the beginning of the current star-formation, and an ionizing photon production rate, ξion, of logξion/erg−1 Hz = 25.3–25.4. Among the sources with EW([CIII]) >= 10 Å, approximately 30% are likely dominated by AGNs. The metallicity derived for galaxies with EW(CIII) = 10–20 Å is low, Z = 0.02–0.2 Z⊙, and the ionization parameter higher (logU ~−1.7) than the average star-forming galaxy. To explain the average UV observations of the strongest but rarest [CIII] emitters (EW([CIII]) > 20 Å), we find that stellar photoionization is clearly insufficient. A radiation field consisting of a mix of a young stellar population (logξion/erg−1 Hz ~ 25.7) plus an AGN component is required. Furthermore an enhanced C/O abundance ratio (up to the solar value) is needed for metallicities Z = 0.1–0.2 Z⊙ and logU = −1.7 to − 1.5. Conclusions. A large grid of photoionization models has allowed us to propose new diagnostic diagrams to classify the nature of the ionizing radiation field (star formation or AGN) of distant galaxies using UV emission lines, and to constrain their ISM properties. We have applied this grid to a sample of [CIII]-emitting galaxies at z = 2–4 detected in VUDS, finding a range of physical properties and clear evidence for significant AGN contribution in rare sources with very strong [CIII] emission. The UV diagnostics we propose should also serve as an important basis for the interpretation of upcoming observations of high-redshift galaxies.

scholarly journals 3D chemical structure of diffuse turbulent ISM

2020 ◽  
Vol 643 ◽  
pp. A36 ◽  
Author(s):  
E. Bellomi ◽  
B. Godard ◽  
P. Hennebelle ◽  
V. Valdivia ◽  
G. Pineau des Forêts ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radiation Field ◽  
Uv Radiation ◽  
Large Scale ◽  
Statistical Properties ◽  
Line Of Sight ◽  
Neutral Medium ◽  
Chemical Information ◽  
Wide Range ◽  
The Magnetic Field

Context. The amount of data collected by spectrometers from radio to ultraviolet (UV) wavelengths opens a new era where the statistical and chemical information contained in the observations can be used concomitantly to investigate the thermodynamical state and the evolution of the interstellar medium (ISM). Aims. In this paper, we study the statistical properties of the HI-to-H2 transition observed in absorption in the local diffuse and multiphase ISM. Our goal is to identify the physical processes that control the probability of occurrence of any line of sight and the origins of the variations of the integrated molecular fraction from one line of sight to another. Methods. The turbulent diffuse ISM is modeled using the RAMSES code, which includes detailed treatments of the magnetohydrodynamics, the thermal evolution of the gas, and the chemistry of H2. The impacts of the UV radiation field, the mean density, the turbulent forcing, the integral scale, the magnetic field, and the gravity on the molecular content of the gas are explored through a parametric study that covers a wide range of physical conditions. The statistics of the HI-to-H2 transition are interpreted through analytical prescriptions and compared with the observations using a modified and robust version of the Kolmogorov-Smirnov test. Results. The analysis of the observed background sources shows that the lengths of the lines of sight follow a flat distribution in logarithmic scale from ~100 pc to ~3 kpc. Without taking into account any variation of the parameters along a line of sight or from one line of sight to another, the results of one simulation, convolved with the distribution of distances of the observational sample, are able to simultaneously explain the position, the width, the dispersion, and most of the statistical properties of the HI-to-H2 transition observed in the local ISM. The tightest agreement is obtained for a neutral diffuse gas modeled over ~200 pc, with a mean density n̅H̅ = 1−2 cm−3, illuminated by the standard interstellar UV radiation field, and stirred up by a large-scale compressive turbulent forcing. Within this configuration, the 2D probability histogram of the column densities of H and H2, poetically called the kingfisher diagram, is remarkably stable and is almost unaltered by gravity, the strength of the turbulent forcing, the resolution of the simulation, or the strength of the magnetic field Bx, as long as Bx < 4 μG. The weak effect of the resolution and our analytical prescription suggest that the column densities of HI are likely built up in large-scale warm neutral medium and cold neutral medium (CNM) structures correlated in density over ~20 pc and ~10 pc, respectively, while those of H2 are built up in CNM structures between ~3 and ~10 pc. Conclusions. Combining the chemical and statistical information contained in the observations of HI and H2 sheds new light on the study of the diffuse matter. Applying this new tool to several atomic and molecular species is a promising perspective to understanding the effects of turbulence, magnetic field, thermal instability, and gravity on the formation and evolution of molecular clouds.

scholarly journals Constraining physical conditions for the PDR of Trumpler 14 in the Carina Nebula

2018 ◽  
Vol 618 ◽  
pp. A53 ◽  
Author(s):  
Ronin Wu ◽  
Emeric Bron ◽  
Takashi Onaka ◽  
Franck Le Petit ◽  
Frédéric Galliano ◽  
...  
Keyword(s):  
Uv Radiation ◽  
Massive Stars ◽  
Local Heating ◽  
Spectral Lines ◽  
Ionization Front ◽  
Thermal Pressure ◽  
Line Energy ◽  
Physical Conditions ◽  
Radiation Fields ◽  
Carina Nebula

We investigate the physical conditions of the CO gas, based on the submillimeter imaging spectroscopy from a 2′ × 7′ (1.5 × 5 pc2) area near the young star cluster, Trumpler 14 of the Carina Nebula. The observations presented in this work are taken with the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) onboard the Herschel Space Observatory. The newly observed spectral lines include [CI] 370 μm [CI] 609 μm, and CO transitions from J = 4−3 to J = 13−12. Our field of view covers the edge of a cavity carved by Trumpler 14 about 1 Myr ago and marks the transition from H ii regions to photo-dissociation regions. The observed CO intensities are the most prominent at the northwest region, Car I-E. With the state-of-the-art Meudon PDR code, we successfully derive the physical conditions, which include the thermal pressure (P) and the scaling factor of radiation fields (GUV), from the observed CO spectral line energy distributions (SLEDs) in the observed region. The derived GUV values generally show excellent agreement with the UV radiation fields created by nearby OB-stars and thus confirm that the main excitation source of the observed CO emission is the UV-photons provided by the massive stars. The derived thermal pressure is in the range 0.5−3 × 108 K cm-3 with the highest values found along the ionization front in Car I-E region facing Trumpler 14, hinting that the cloud structure is similar to the recent observations of the Orion Bar. We also note a discrepancy at a local position (<0.17 × 0.17 pc2) between the photo-dissociation region (PDR) modeling result and the UV radiation fields estimated from nearby massive stars, which requires further investigation on nearby objects that could contribute to local heating, including outflow. Comparing the derived thermal pressure with the radiation fields, we report the first observationally derived and spatially resolved P ~ 2 × 104 GUV relationship. As direct comparisons of the modeling results to the observed 13CO, [O I] 63 μm, and [C II] 158 μm intensities are not straightforward, we urge the reader to be cautious when constraining the physical conditions of PDRs with combinations of 12CO, 13CO, [C I], [O I] 63 μm, and [C II] 158 μm observations.

scholarly journals Analysis of the Interstellar Medium Properties of the Herschel Reference Survey Galaxies

2012 ◽  
Vol 8 (S292) ◽  
pp. 284-284
Author(s):  
Laure Ciesla ◽  
Keyword(s):  
Interstellar Medium ◽  
Physical Properties ◽  
Radiation Field ◽  
Statistical Study ◽  
Dust Mass ◽  
Multi Wavelength ◽  
Nearby Galaxies ◽  
Photodissociation Regions ◽  
K Band

AbstractThe Herschel Reference Survey is a guaranteed time key project aimed at studying the physical properties of the interstellar medium (ISM) of 323 nearby galaxies, covered by multi-wavelength data. This volume limited, K-band selected sample is composed of galaxies spanning the whole range of morphological types and environments. We conduct a statistical study on the ISM properties of nearby galaxies based on the analysis of their SED. To achieve this goal, we fit the data with the models of Draine & Li (2007) to obtain the intensity of interstellar radiation field, the PAH abundance, the contribution of photodissociation regions, and the dust mass.

scholarly journals THE MODIFICATION OF PHYSICAL PROPERTIES OF THE SOIL UNDER THE INFLUENCE OF SOME CONVENTIONAL AND UNCONVENTIONAL TILLAGE SYSTEMS AND CORRELATION BETWEEN SOME OF THE SOIL COMPACTATION INDICATORS AND YIELDS

1970 ◽  
Vol 63 ◽  
Author(s):  
L. Raus ◽  
G. Jitareanu
Keyword(s):  
Physical Properties ◽  
Soil Properties ◽  
Management Practice ◽  
Soil Bulk Density ◽  
Physical Conditions ◽  
Complex Interactions ◽  
Tillage System ◽  
Tillage Operation ◽  
Crop Parameters ◽  
Properties Of Soil

Optimal crop rooting soil physical conditions are a result of complex interactions between soil strength and oxygen and water supply to plant roots. Spatial/temporal variability in soil properties can be critical in the evaluation of the effects of tillage management practice on soil and crop parameters. In this paper tillage were evaluated for theirs effects on soil physical and hydrological properties. Tillage treatments were plough to 20 cm, plough to 30 cm, chisel and disc harrow applied to wheat in to been/ wheat/ maize rotation. The experiments have been conducted in the Didactic Station of the USAMV – Iasi, Ezăreni Farm, during the period between 2002-2004, on a cambic chernozem with 3,4 % humus and pH 7. Tillage system modify, at least temporarily, some of the physical properties of soil, such as soil bulk density, penetration resistance, soil porosity and soil structural stability. Hydraulic properties of the soil did not differ significantly. All the tillage operation was significantly different in their effects on soil properties.

scholarly journals How Identifying Circumgalactic Gas by Line-of-sight Velocity instead of the Location in 3D Space Affects O vi Measurements

2021 ◽  
Vol 923 (2) ◽  
pp. 137
Author(s):  
Stephanie H. Ho ◽  
Crystal L. Martin ◽  
Joop Schaye
Keyword(s):  
High Resolution ◽  
Density Profile ◽  
Column Density ◽  
Line Of Sight ◽  
Lower Mass ◽  
Star Forming ◽  
3D Space ◽  
High Incidence ◽  
High Incidence Rate ◽  
Stellar Masses

Abstract The high incidence rate of the O vi λλ1032, 1038 absorption around low-redshift, ∼L * star-forming galaxies has generated interest in studies of the circumgalactic medium. We use the high-resolution EAGLE cosmological simulation to analyze the circumgalactic O vi gas around z ≈ 0.3 star-forming galaxies. Motivated by the limitation that observations do not reveal where the gas lies along the line of sight, we compare the O vi measurements produced by gas within fixed distances around galaxies and by gas selected using line-of-sight velocity cuts commonly adopted by observers. We show that gas selected by a velocity cut of ±300 km s−1 or ±500 km s−1 produces a higher O vi column density, a flatter column density profile, and a higher covering fraction compared to gas within 1, 2, or 3 times the virial radius (r vir) of galaxies. The discrepancy increases with impact parameter and worsens for lower-mass galaxies. For example, compared to the gas within 2 r vir, identifying the gas using velocity cuts of 200–500 km s−1 increases the O vi column density by 0.2 dex (0.1 dex) at 1 r vir to over 0.75 dex (0.7 dex) at ≈ 2 r vir for galaxies with stellar masses of 109–109.5 M ⊙ (1010–1010.5 M ⊙). We furthermore estimate that excluding O vi outside r vir decreases the circumgalactic oxygen mass measured by Tumlinson et al. (2011) by over 50%. Our results demonstrate that gas at large line-of-sight separations but selected by conventional velocity windows has significant effects on the O vi measurements and may not be observationally distinguishable from gas near the galaxies.

scholarly journals Compton-Thick AGN in the NuSTAR ERA VII. A joint NuSTAR, Chandra, and XMM-Newton Analysis of Two Nearby, Heavily Obscured Sources

2021 ◽  
Vol 922 (2) ◽  
pp. 159
Author(s):  
A. Traina ◽  
S. Marchesi ◽  
C. Vignali ◽  
N. Torres-Albà ◽  
M. Ajello ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Energy Range ◽  
Active Galactic Nuclei ◽  
Column Density ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Line Of Sight ◽  
Broad Energy Range ◽  
Larger Sample ◽  
Broad Energy

Abstract We present the joint Chandra, XMM-Newton, and NuSTAR analysis of two nearby Seyfert galaxies, NGC 3081 and ESO 565-G019. These are the only two having Chandra data in a larger sample of 10 low-redshift (z ≤ 0.05), candidates Compton-thick (CT) Active Galactic Nuclei selected in the 15–150 keV band with Swift-BAT that were still lacking NuSTAR data. Our spectral analysis, performed using physically motivated models, provides an estimate of both the line-of-sight (l.o.s.) and average (N H,S ) column densities of the two torii. NGC 3081 has a Compton-thin l.o.s. column density N H,z = [0.58–0.62] × 1024 cm−2, but the N H,S , beyond the CT threshold (N H,S = [1.41–1.78] × 1024 cm−2), suggests a “patchy” scenario for the distribution of the circumnuclear matter. ESO 565-G019 has both CT l.o.s. and N H,S column densities (N H,z > 2.31 × 1024 cm−2 and N H,S > 2.57 × 1024 cm−2, respectively). The use of physically motivated models, coupled with the broad energy range covered by the data (0.6–70 keV and 0.6–40 keV, for NGC 3081 and ESO 565-G019, respectively) allows us to constrain the covering factor of the obscuring material, which is C TOR = [0.63–0.82] for NGC 3081, and C TOR = [0.39–0.65] for ESO 565-G019.

scholarly journals IX. Preliminary notice of further researches on the physical properties of matter in the liquid and gaseous states under varied conditions of pressure and temperature

1875 ◽  
Vol 23 (156-163) ◽  
pp. 514-521 ◽  
Keyword(s):  
Physical Properties ◽  
Gaseous State ◽  
Physical Conditions ◽  
Different Temperatures

The investigation to which this note refers has occupied me, with little intermission, since my former communication in 1869 to the Society, “On the Continuity of the Liquid and Gaseous States of Matter.” It was undertaken chiefly to ascertain the modifications which the three great laws discovered respectively by Boyle, Gay-Lussac, and Dalton undergo when matter in the gaseous state is placed under physical conditions differing greatly from any hitherto within the reach of observation. It embraces a large number of experiments of precision, performed at different temperatures and at pressures ranging from twelve to nearly three hundred atmospheres.

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