scholarly journals Observations of [OI]63 μm line emission in main-sequence galaxies at z ∼ 1.5

2020 ◽  
Vol 499 (2) ◽  
pp. 1788-1794
Author(s):  
J Wagg ◽  
M Aravena ◽  
D Brisbin ◽  
I Valtchanov ◽  
C Carilli ◽  
...  
Keyword(s):  
Field Strength ◽  
Interstellar Medium ◽  
Radiation Field ◽  
Uv Radiation ◽  
Main Sequence ◽  
Line Emission ◽  
The Other ◽  
Low Density ◽  
Star Forming ◽  
Neutral Gas

ABSTRACT We present Herschel–PACS spectroscopy of four main-sequence star-forming galaxies at z ∼ 1.5. We detect [OI]63 μm line emission in BzK-21000 at z = 1.5213, and measure a line luminosity, $L_{\rm [O\, {\small I}]63\, \mu m} = (3.9\pm 0.7)\times 10^9$ L⊙. Our PDR modelling of the interstellar medium in BzK-21000 suggests a UV radiation field strength, G ∼ 320G0, and gas density, n ∼ 1800 cm−3, consistent with previous LVG modelling of the molecular CO line excitation. The other three targets in our sample are individually undetected in these data, and we perform a spectral stacking analysis which yields a detection of their average emission and an [O i]63 μm line luminosity, $L_{\rm [O\, {\small I}]63\, \mu m} = (1.1\pm 0.2)\times 10^9$ L⊙. We find that the implied luminosity ratio, $L_{\rm [O\, {\small I}]63\, \mu m}/L_{\rm IR}$, of the undetected BzK-selected star-forming galaxies broadly agrees with that of low-redshift star-forming galaxies, while BzK-21000 has a similar ratio to that of a dusty star-forming galaxy at z ∼ 6. The high [O i]63 μm line luminosities observed in BzK-21000 and the z ∼ 1−3 dusty and sub-mm luminous star-forming galaxies may be associated with extended reservoirs of low density, cool neutral gas.

scholarly journals The Morphology and Physics of the Local Interstellar Medium

1996 ◽  
Vol 152 ◽  
pp. 261-268 ◽  
Author(s):  
Fredrick C. Bruhweiler
Keyword(s):  
Interstellar Medium ◽  
Radiation Field ◽  
Special Role ◽  
Low Density ◽  
The Sun ◽  
Local Interstellar Medium ◽  
Density Region ◽  
Direct Measurements ◽  
Extreme Uv ◽  
Local Cloud

We are finally on the threshold of obtaining a coherent morphological and physical picture for the local interstellar medium (LISM), especially the region within 300 pc of the Sun. The EUVE is playing a special role in revealing this picture. This instrument can provide direct measurements of the the radiation field that photoionizes both hydrogen and helium. It also can yield direct measurements of the column densities of hydrogen, but especially He I and He II toward nearby white dwarfs. These observations suggest that the ionization in the Local Cloud, the cloud in which the Sun is embedded, is not in equilibrium, but in a recombination phase. Heuristic calculations imply that the the present ionization is due to the passage of shocks, at times greater than 3 × 106 years ago. The origin of these shocks are probably linked to the supernova which was responsible for the expanding nebular complex of clouds know as the Loop I supernova remnant, of which the Local Cloud is a part, extreme- UV radiation field, that which ionizes both hydrogen and helium in the LISM. Of the ISM within 300 pc, the volume appears to be predominantly filled by hot (106 K) coronal gas. This gas is laced with six largescale shell structures with diameters ~100−150 pc including the long-recognized radio loops, Loop I−IV, as well as the Orion-Eridanus and Gum Nebulae are identified. An idea that has evolved in the literature for over two decades is that the kinematically-linked OB associations representing Gould’s Belt, plus the gas and dust of Lindblad’s Ring, require that previous supernova activity and stellar winds carved out a 400–600 pc diameter cavity some 3 to 6 × 107 yr ago. This activity produced a pre-existing low density region, into which the present young loop structures have expanded. The outer boundaries of the identified expanding loop structures, inside this preexisting cavity, delineate the periphery of the the mis-named “local interstellar bubble.” Thus, this picture naturally explains some of the problems often associated with the presence of this low density region exterior to Loop I.

The Interstellar Medium in LSB Galaxies

1999 ◽  
Vol 171 ◽  
pp. 161-168
Author(s):  
W.J.G. de Blok
Keyword(s):  
Interstellar Medium ◽  
The Other ◽  
Molecular Gas ◽  
Low Density ◽  
Slow Evolution ◽  
Lsb Galaxies

AbstractI describe the properties of the interstellar medium in LSB galaxies, and conclude that apart from low density the other important factor determining the slow evolution of LSB galaxies is the metallicity, and (due to inefficient cooling) the corresponding lack of large amounts of molecular gas.

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 Interstellar Medium in Star Burst Galaxies

1987 ◽  
Vol 115 ◽  
pp. 614-614
Author(s):  
R. Genzel ◽  
J. B. Lugten ◽  
M. K. Crawford ◽  
D. M. Watson
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Line Emission ◽  
Far Infrared ◽  
High Rate ◽  
Interstellar Gas ◽  
Infrared Observations ◽  
Bolometric Luminosity ◽  
Neutral Gas ◽  
Molecular Lines

We report far-infrared observations of [0 I], [C II] and [O III] fine structure emission lines toward the nuclei of M82 and 7 other galaxies with a high rate of star formation. The far-infrared line emission is bright, contains about 0.5% of the bolometric luminosity in the central 60″, and is spatially concentrated toward the nuclei. In these galaxies between 10 and 30% of the interstellar gas near the nuclei is contained in a warm, atomic component. This atomic gas is probably located at the UV photodissociated surfaces of molecular clouds. The neutral gas in M82 has a temperature of ∼ 200 K, hydrogen density of ∼ 3 × 104 cm−3 and is very clumpy, indicating that the interstellar medium in this star burst galaxy is very different from that in the disk of our own galaxy. We discuss the implications of the infrared observations for the interpretation of mm molecular lines and for star formation at the nuclei of star burst galaxies.

The X-ray binary populations of M81 and M82

2018 ◽  
Vol 14 (S346) ◽  
pp. 344-349
Author(s):  
Paul H. Sell ◽  
Andreas Zezas ◽  
Stephen J. Williams ◽  
Jeff J. Andrews ◽  
Kosmas Gazeas ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Globular Clusters ◽  
Luminosity Function ◽  
Main Sequence ◽  
The Other ◽  
High Mass ◽  
Early Type ◽  
X Ray ◽  
Star Forming ◽  
Low Mass

AbstractWe use deep Chandra and HST data to uniquely classify the X-ray binary (XRB) populations in M81 on the basis of their donor stars and local stellar populations (into early-type main sequence, yellow giant, supergiant, low-mass, and globular cluster). First, we find that more massive, redder, and denser globular clusters are more likely to be associated with XRBs. Second, we find that the high-mass XRBs (HMXBs) overall have a steeper X-ray luminosity function (XLF) than the canonical star-forming galaxy XLF, though there is some evidence of variations in the slopes of the sub-populations. On the other hand, the XLF of the prototypical starburst M82 is described by the canonical powerlaw (αcum ∼ 0.6) down to LX ∼ 1036 erg s−1. We attribute variations in XLF slopes to different mass transfer modes (Roche-lobe overflow versus wind-fed systems).

scholarly journals Proplyds in the Flame Nebula NGC 2024

2020 ◽  
Author(s):  
Thomas J Haworth ◽  
Jinyoung S Kim ◽  
Andrew J Winter ◽  
Dean C Hines ◽  
Cathie J Clarke ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Detection Rate ◽  
Planet Formation ◽  
The Other ◽  
Recent Survey ◽  
Western Region ◽  
Eastern Region ◽  
Western Population ◽  
Star Forming ◽  
Dense Cloud

Abstract A recent survey of the inner 0.35 × 0.35 pc of the NGC 2024 star forming region revealed two distinct millimetre continuum disc populations that appear to be spatially segregated by the boundary of a dense cloud. The eastern (and more embedded) population is ∼0.2 − 0.5 Myr old, with an ALMA mm continuum disc detection rate of about 45 per cent. However this drops to only ∼15 per cent in the 1 Myr western population. When these distinct populations were presented it was suggested that the two main UV sources, IRS 1 (a B0.5V star in the western region) and IRS 2b (an O8V star in the eastern region, but embedded) have both been evaporating the discs in the depleted western population. In this paper we report the firm discovery in archival HST data of 4 proplyds and 4 further candidate proplyds in NGC 2024, confirming that external photoevaporation of discs is occurring. However, the locations of these proplyds changes the picture. Only three of them are in the depleted western population and their evaporation is dominated by IRS 1, with no obvious impact from IRS 2b. The other 5 proplyds are in the younger eastern region and being evaporated by IRS 2b. We propose that both populations are subject to significant external photoevaporation, which happens throughout the region wherever discs are not sufficiently shielded by the interstellar medium. The external photoevaporation and severe depletion of mm grains in the 0.2-0.5 Myr eastern part of NGC 2024 would be in competition even with very early planet formation.

scholarly journals Full of Orions: a 200-pc mapping of the interstellar medium in the redshift-3 lensed dusty star-forming galaxy SDP.81

2020 ◽  
Vol 494 (4) ◽  
pp. 5542-5567 ◽  
Author(s):  
Matus Rybak ◽  
J A Hodge ◽  
S Vegetti ◽  
P van der Werf ◽  
P Andreani ◽  
...  
Keyword(s):  
Field Strength ◽  
Interstellar Medium ◽  
Far Infrared ◽  
Source Plane ◽  
Star Forming ◽  
Physical Conditions ◽  
Orion Trapezium ◽  
Thermal Saturation ◽  
Continuum Data ◽  
Far Ultraviolet

ABSTRACT We present a sub-kpc resolved study of the interstellar medium properties in SDP.81, a $z$ = 3.042 strongly gravitationally lensed, dusty star-forming galaxy, based on high-resolution, multiband ALMA observations of the far-infrared (FIR) continuum, CO ladder, and the [C ii] line. Using a visibility-plane lens modelling code, we achieve a median source-plane resolution of ∼200 pc. We use photon-dominated region (PDR) models to infer the physical conditions – far-ultraviolet (FUV) field strength, density, and PDR surface temperature – of the star-forming gas on 200-pc scales, finding a FUV field strength of ∼103−104G0, gas density of ∼105 cm−3, and cloud surface temperatures up to 1500 K, similar to those in the Orion Trapezium region. The [C ii] emission is significantly more extended than that FIR continuum: ∼50 per cent of [C ii] emission arises outside the FIR-bright region. The resolved [C ii]/FIR ratio varies by almost 2 dex across the source, down to ∼2 × 10−4 in the star-forming clumps. The observed [C ii]/FIR deficit trend is consistent with thermal saturation of the C+ fine-structure-level occupancy at high gas temperatures. We make the source-plane reconstructions of all emission lines and continuum data publicly available.

scholarly journals Star Formation & Molecular Gas over Cosmic Time

2012 ◽  
Vol 8 (S295) ◽  
pp. 64-73 ◽  
Author(s):  
E. Daddi ◽  
M. T. Sargent ◽  
M. Béthermin ◽  
G. Magdis
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Main Sequence ◽  
Formation Rate ◽  
Line Emission ◽  
Cosmic Time ◽  
Gas Content ◽  
Molecular Gas ◽  
Simple Description ◽  
Star Forming

AbstractRecent observations have revealed the existence of a ‘main sequence’ of star-forming galaxies out to high redshift. While the majority of star-forming galaxies are observed to be close to this relation between star formation rate (SFR) and stellar mass, a smaller subset of the population – so-called ‘starbursts’ – displays specific star-formation rates and star-formation efficiencies that exceed those of normal (main-sequence) galaxies by up to an order of magnitude. A large degree of homogeneity and similarity has been observed for the properties of the population of normal galaxies across a broad redshift range, including a narrow correlation between their CO luminosity (hence gas content) and IR luminosity and an almost invariable IR SED getting warmer with redshift, while starburst galaxies display systematically different properties. This can be used to devise a simple description of the evolution of the star-forming galaxy population since z ~ 2 and, with a higher degree of uncertainty, even further back in time, in a scheme that we dub two star formation mode framework (2-SFM). We show how this can successfully reproduce the shape of the IR luminosity function of galaxies as a function of redshifts, and the IR number counts. Furthermore, we can link the cosmic evolution of the sSFR of main-sequence galaxies to the evolution of the molecular fuel reservoir and to derive estimates of the molecular gas mass functions of star-forming galaxies that are based on their empirically measured gas properties rather than simulations or semi-analytical modelling. We also infer the evolution of the cosmic abundance of molecular gas and briefly discuss its expected observational signature by molecular line emission, the CO luminosity function.

scholarly journals The VLT/MUSE view of the central galaxy in Abell 2052

2018 ◽  
Vol 612 ◽  
pp. A19 ◽  
Author(s):  
Barbara Balmaverde ◽  
Alessandro Capetti ◽  
Alessandro Marconi ◽  
Giacomo Venturi
Keyword(s):  
Interstellar Medium ◽  
Line Emission ◽  
Emission Lines ◽  
Expansion Velocity ◽  
Direct Estimate ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
The North ◽  
Integral Field Spectrograph

We report observations of the radio galaxy 3C 317 (at z = 0.0345) located at the center of the Abell cluster A2052, obtained with the VLT/MUSE integral field spectrograph. The Chandra images of this cluster show cavities in the X-ray emitting gas, which were produced by the expansion of the radio lobes inflated by the active galactic nucleus (AGN). Our exquisite MUSE data show with unprecedented detail the complex network of line emitting filaments enshrouding the northern X-ray cavity. We do not detect any emission lines from the southern cavity, with a luminosity asymmetry between the two regions higher than ~75. The emission lines produced by the warm phase of the interstellar medium (WIM) enable us to obtain unique information on the properties of the emitting gas. We find dense gas (up to 270 cm−3) that makes up part of a global quasi spherical outflow that is driven by the radio source, and obtain a direct estimate of the expansion velocity of the cavities (265 km s−1). The emission lines diagnostic rules out ionization from the AGN or from star-forming regions, suggesting instead ionization from slow shocks or from cosmic rays. The striking asymmetric line emission observed between the two cavities contrasts with the less pronounced differences between the north and south sides in the hot gas; this represents a significant new ingredient for our understanding of the process of the exchange of energy between the relativistic plasma and the external medium. We conclude that the expanding radio lobes displace the hot tenuous phase of the interstellar medium (ISM), but also impact the colder and denser ISM phases. These results show the effects of the AGN on its host and the importance of radio mode feedback.

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