The Evolution of Moderately Ionized Gas in the Universe

AbstractThis work is focused on the characterization of the Seyfert-2 galaxies hosting very large, ultra-luminous narrow-line regions (NLRs) at redshifts z = 0.2−0.34. With a space density of 4.4 Gcp−3 at z ∼ 0.3, these “Low Redshift Lyman-α Blob” (LAB) host galaxies are amongst the rarest objects in the universe, and represent an exceptional and short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). We present the study of GMOS spectra for 13 LAB galaxies covering the rest frame spectral range 3700–6700 Å. Predominantly, the [OIII]λ5007 emission line radial distribution is as widespread as that of the continuum one. The emission line profiles exhibit FWHM between 300–700 Km s−1. In 7 of 13 cases a broad kinematical component is detected with FWHM within the range 600–1100 Km s−1. The exceptionally high [OIII]λ5007 luminosity is responsible for very high equivalent width reaching 1500 Å at the nucleus.

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The Interstellar Medium of Dwarf Galaxies

Galaxies ◽

10.3390/galaxies10010011 ◽

2022 ◽

Vol 10 (1) ◽

pp. 11

Author(s):

Christian Henkel ◽

Leslie K. Hunt ◽

Yuri I. Izotov

Keyword(s):

Interstellar Medium ◽

Dwarf Galaxies ◽

Chemical Properties ◽

Physical And Chemical Properties ◽

Ionized Gas ◽

Green Pea ◽

Physical And Chemical ◽

The Impact ◽

The Universe ◽

And Chemical Properties

Dwarf galaxies are by far the most numerous galaxies in the Universe, showing properties that are quite different from those of their larger and more luminous cousins. This review focuses on the physical and chemical properties of the interstellar medium of those dwarfs that are known to host significant amounts of gas and dust. The neutral and ionized gas components and the impact of the dust will be discussed, as well as first indications for the existence of active nuclei in these sources. Cosmological implications are also addressed, considering the primordial helium abundance and the similarity of local Green Pea galaxies with young, sometimes protogalactic sources in the early Universe.

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The 21 cm absorption line profile as a tool for the search for antimatter in the universe

Progress of Theoretical and Experimental Physics ◽

10.1093/ptep/ptu142 ◽

2014 ◽

Vol 2014 (11) ◽

pp. 111E01-111E01 ◽

Cited By ~ 1

Author(s):

D. Solovyev ◽

L. Labzowsky

Keyword(s):

Absorption Line ◽

Line Profile ◽

The Universe

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UV Absorption and Emission Lines from Highly Ionized Gas in the Galactic Halo

Symposium - International Astronomical Union ◽

10.1017/s0074180900088999 ◽

1991 ◽

Vol 144 ◽

pp. 131-141

Author(s):

Blair D. Savage

Keyword(s):

Absorption Line ◽

Flow Rate ◽

Galactic Halo ◽

Galactic Plane ◽

Uv Absorption ◽

Emission Lines ◽

Line Profiles ◽

Ionized Gas ◽

Absorption And Emission ◽

Uv Emission

Highly ionized gas in the galactic halo has been detected through UV absorption and emission lines. In absorption the species studied include Si IV, C IV and N V. The UV emission studies have recorded C IV and O III]. Absorption measurements toward galactic stars reveal that the |z| distribution of the gas is roughly exponential with a scale height of approximately 3 kpc and has column densities perpendicular to the galactic plane of N ~ 2×1013, 1×1014 and 3×1013 atoms cm−2, for Si IV, C IV and NV, respectively. Similar absorption line profiles for these species suggests a common process for their origin. The presence of N V absorption implies the existence of some gas with a temperature near T ~ 2×105 K. The highly ionized absorbing gas toward distant stars in direction b < −50° has simple and relatively narrow line profiles (FWHM ~ 45 to 70 km−1) and small average LSR velocities while the gas in the direction b > 50° reveals a complex pattern of motions with substantial inflow and outflow velocities. Galactic rotation has an appreciable effect on the absorption line profiles to very distant stars located in the low halo. C IV emission has been seen at greater than a 3σ level of significance in 4 of 8 directions. The emission brightens toward the galactic poles and has a polar intensity I(C IV) ~ 5000 photons cm−2s−1ster−1. If the emitting and absorbing gas coincide in space the measurements imply ne ~ 0.01 cm−3 and P/k ~ 2000 cm−3 K for gas with T ~ 105 K. This phase of the gas fills only a small volume of the space (f ~ 0.03) and accounts for only a small fraction of the total column density of gas perpendicular to the galactic plane [~3×1018 atoms cm −2 vs 3.5×1020 atoms cm −2 for H I and 1×1020 atoms cm −2 for H+]. However, the gas provides a large EUV/UV emission line flux (~1×10−5erg. cm−2 s−1) which corresponds to a H I ionizing flux of ~2×105 ionizations cm−2 s−1. Gas with T near 2×105 K cools very rapidly. Its origin may be associated with the cooling gas of a galactic fountain flow or with thermal condensations in cosmic ray driven fountains. In the nonequilbrium cooling of a Galactic fountain, a flow rate of 4 MO/ year to each side of the Galaxy is required to produce the amount of N V absorption found in the halo while a flow rate 5x larger is required to produce the observed level of C IV emission.

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The Evolution of Neutral Gas in the Universe

Proceedings of the International Astronomical Union ◽

10.1017/s1743921306010611 ◽

2006 ◽

Vol 2 (S235) ◽

pp. 440-440

Author(s):

David Turnshek ◽

Sandhya Rao ◽

Eric Monier ◽

Daniel Nestor ◽

Anna Quider

Keyword(s):

Absorption Line ◽

Hubble Space Telescope ◽

Reference List ◽

Space Telescope ◽

Neutral Gas ◽

The Universe ◽

Initial Results ◽

Gas Component

AbstractWe give references to some of our work on the properties and evolution of the neutral gas component of the Universe (see reference list). The bulk of the observed neutral gas has been detected by identifying intervening damped Lyα (DLA) quasar absorption-line systems with N(H) ≥2 × 1020 atoms cm−2. We also present some initial results from a program to identify DLA absorbers near redshift z = 0.5 using Hubble Space Telescope ACS prism spectra (see Figure 1).

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Abundances fromz=0 toz=5

Symposium - International Astronomical Union ◽

10.1017/s0074180900113816 ◽

2002 ◽

Vol 187 ◽

pp. 109-115

Author(s):

Donald G. York

Keyword(s):

Absorption Line ◽

Milky Way ◽

Magellanic Clouds ◽

Type I ◽

Lyman Alpha ◽

Damped Lyman Alpha Systems ◽

The Universe ◽

Milky Way Halo

Interstellar abundances are compared for the Milky Way disk, the Milky Way halo, the Large and Small Magellanic Clouds and the damped Lyman alpha systems among the QSO absorption line systems. While a new set of observational aspects of element formation in the Universe is emerging, including a dearth of formation activity fromz=5 toz=3, the predicted signal of [Si/Fe] decreasing from highzto lowz, as Type I supernovae start contributing to Fe production, has not yet been seen.

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Understanding the Spatial Distributions of the Ionic/Atomic/Molecular/Dust Components in PNe

Galaxies ◽

10.3390/galaxies7010010 ◽

2019 ◽

Vol 7 (1) ◽

pp. 10

Author(s):

Toshiya Ueta ◽

Masaaki Otsuka ◽

Keyword(s):

Central Star ◽

H Ii Regions ◽

Data Sets ◽

Ionized Gas ◽

X Ray ◽

Neutral Gas ◽

Photoionization Model ◽

The Universe ◽

Circumstellar Environment ◽

Do So

Planetary nebulae (PNe) are often recognized as the hallmark of compact H ii regions in the Universe. However, there exist dusty neutral regions extending beyond the central ionized region. We demonstrate that such dusty neutral regions (also known as photo-dissociation regions, or PDRs) around the central ionized region are significant parts of PNe in terms of energetics and mass. We do so by using our latest dusty photoionization model of NGC 6781 (of 13 parameters) based on one of the most comprehensive panchromatic data sets ever assembled for a PN encompassing from X-ray to radio (of 136 constraining data, including 19 flux densities, 78 line fluxes, and 37 band fluxes). We find that NGC 6781, evolved out of a 2.25–3.0 M ⊙ star located 460 pc away from us, possesses a massive concentration of neutral gas (molecular hydrogen) just beyond the central ionized region and that the amount of ionized gas in NGC 6781 is only 22% of the observationally accounted amount of matter in the circumstellar environment, which itself does not even account for the amount of mass presumably ejected by the central star during the last thermal pulse event according to the latest evolutionary models. This means that the observed nebula in this PN is only the tip of the iceberg.

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Local HI: Constraints on the Evolution of the HI Content of the Universe

Publications of the Astronomical Society of Australia ◽

10.1071/as97031 ◽

1997 ◽

Vol 14 (1) ◽

pp. 31-36 ◽

Cited By ~ 4

Author(s):

F. H. Briggs

Keyword(s):

Star Formation ◽

Absorption Line ◽

Galaxy Evolution ◽

Column Density ◽

Absorption Lines ◽

Reliable Measure ◽

Redshift Range ◽

Neutral Gas ◽

Present Rate ◽

The Universe

AbstractAnalyses of QSO absorption lines show that the HI content has evolved over the redshift range z = 5 to z = 0. The 21-cm line measurements of the z = 0 HI content avoid several biases inherent in the absorption-line technique, such as the influence of evolving dust content in the absorbers, and will produce a reliable measure to anchor theories of galaxy evolution. Examples of important questions to be addressed by local HI surveys are: (1) Is there a significant population of gas-rich galaxies or intergalactic clouds that is missing from the census of optically selected galaxies? (2) Is there an adequate reservoir of neutral gas to substantially prolong star formation at its present rate? (3) Are there massive objects of such low HI column density that they can have escaped detection in the ‘unbiased’ HI surveys that have been conducted so far?

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A Decoupled Nucleus in NGC 1052

Symposium - International Astronomical Union ◽

10.1017/s0074180900109519 ◽

1995 ◽

Vol 164 ◽

pp. 438-438

Author(s):

O.K. Sil'chenko

Keyword(s):

Absorption Line ◽

Spectral Range ◽

Equivalent Width ◽

Two Dimensional ◽

Ionized Gas ◽

Radial Profiles ◽

Line Equivalent Width

The central part of NGC 1052 has been observed at the prime focus of the 6m telescope with the Multi-Pupil Spectrophotometer equipped with a two-dimensional IPCS. Ninety-nine spectra over the central 14.5″x11″ are registered in the spectral range of λλ4700 – 5400 AA and are used to map ionized-gas velocities (by [OIII]λ5007) and to derive radial profiles of absorption-line equivalent width for MgIλA5175, FeIλ5270, and Hβ.

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QUASAR CLUSTERING AND ITS COSMOLOGICAL IMPLICATION

International Journal of Modern Physics A ◽

10.1142/s0217751x89001394 ◽

1989 ◽

Vol 04 (14) ◽

pp. 3477-3502 ◽

Cited By ~ 1

Author(s):

LI ZHI FANG

Keyword(s):

Structure Formation ◽

Absorption Line ◽

Large Scale ◽

Total Density ◽

Density Inhomogeneity ◽

Large Scale Structures ◽

Cosmological Implication ◽

Galaxy Distribution ◽

Scale Structures ◽

The Universe

The clusterings of quasars and absorption line clouds have been analyzed from the viewpoint of the structure formation of the universe. It was found that the features of quasar clustering are quite different from those of galaxies. These results have already given several meaningful constraints on the structure formation, as follows: (a) quasar clustering is much weaker than in galaxies; (b) large scale structures, such as superclusters, should probably be formed after the epoch z~2; (c) the amplitude of the total density inhomogeneity seems to be less than that of galaxy distribution by at least a factor of 3–5 (in a Ω=1 universe); (d) Ly-α absorption clouds may be formed by different processes of clustering from that of glaxies.

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