Emission Lines: Sign of a New Energy Source?

Symposium - International Astronomical Union ◽

10.1017/s0074180900027352 ◽

1982 ◽

Vol 97 ◽

pp. 69-70

Author(s):

David S. De Young

Keyword(s):

Energy Source ◽

Interstellar Medium ◽

Emission Line ◽

Emission Lines ◽

Class I ◽

Radio Sources ◽

Extended Radio ◽

New Energy ◽

Centaurus A

In addition to the occurrence of emission line regions coexistent with extended radio sources which have been discussed at this Symposium, this phenomenon has been observed earlier in 3C277.3 (Miley et al. 1981) and in Centaurus A (Graham and Price 1981). This gas has been detected only in the Fanaroff and Riley “Class I” radio sources. Data concerning this class of object suggest that outflow from the nucleus is proceeding at transonic or subsonic speeds and this correlation has led to the suggestion (De Young 1981) that the origin of the emission line gas arises from entrainment of the interstellar medium into the ejected material.

Download Full-text

Challenges and Techniques for Simulating Line Emission

Galaxies ◽

10.3390/galaxies6040100 ◽

2018 ◽

Vol 6 (4) ◽

pp. 100 ◽

Cited By ~ 8

Author(s):

Karen Olsen ◽

Andrea Pallottini ◽

Aida Wofford ◽

Marios Chatzikos ◽

Mitchell Revalski ◽

...

Keyword(s):

Interstellar Medium ◽

Emission Line ◽

Line Emission ◽

Emission Lines ◽

Synthetic Spectra ◽

Recent Advances ◽

The Future ◽

Important Quality ◽

Circumgalactic Medium

Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of “Walking the Line”, a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.

Download Full-text

Large Scale Jets in Class I and Class II Radio Sources and Quasars

Highlights of Astronomy ◽

10.1017/s1539299600008078 ◽

1989 ◽

Vol 8 ◽

pp. 409-416

Author(s):

G.V. Bicknell

Keyword(s):

Interstellar Medium ◽

Surface Brightness ◽

Large Scale ◽

External Medium ◽

Class Ii ◽

Class I ◽

Radio Sources ◽

Speed Of Light ◽

Slow Surface ◽

Quasar Jets

ABSTRACTThe physics of large scale jets in class I and class II extragalactic radio sources and quasars is discussed. Class I jets appear to be turbulent, transonic jets which entrain the interstellar medium. The related jet deceleration causes a slow surface brightness decline which is usually observed. Class II jets are supersonic and terminate in an advancing shock against the external medium. Both types of jet are initially light but the ratio of jet density to external density of class I jets increases owing to entrainment. It is quite plausible that quasar jets are hypersonic and light and this may solve problems of confinement. The velocities of class I jets are of the order of a few thousand kilometers per second. Class II and quasar jets may be at least mildly relativistic. However, it is not clear whether the velocities of large scale jets in powerful sources are close to the speed of light. Recent depolarization measurements provide an interesting focus for discussion of this question.

Download Full-text

Jets and Broad Emission Line Regions

Symposium - International Astronomical Union ◽

10.1017/s007418090007813x ◽

1984 ◽

Vol 110 ◽

pp. 237-238

Author(s):

Peter Barthel ◽

Colin Norman ◽

George Miley

Keyword(s):

Emission Line ◽

Relative Orientation ◽

Radio Sources ◽

Broad Emission ◽

Relativistic Beam ◽

Extended Radio ◽

Broad Emission Line

In recent years an elegant hypothesis for a unified scheme for compact and extended radio sources, and also radio quiet QSOs and radio loud Quasars has been developed (Scheuer & Readhead 1979, Orr & Brown 1982). In this scheme the relative orientation of (relativistic) beam and observer is thought to explain the observed source morphology. We feel that observations suggest examining compact and extended radio sources from still another “angle”.

Download Full-text

Compact Radio Sources in the Nuclei of Elliptical Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900005556 ◽

1972 ◽

Vol 44 ◽

pp. 222-223 ◽

Cited By ~ 1

Author(s):

R. D. Ekers

Keyword(s):

Radio Emission ◽

Angular Size ◽

Optical Emission ◽

Elliptical Galaxies ◽

Emission Lines ◽

Radio Sources ◽

Radio Luminosity ◽

Compact Source ◽

Extended Radio

Ten percent of the intrinsically bright elliptical galaxies contain compact radio sources (angular size < 3 arc sec) with radio luminosity ∼ 1040 erg s−1. The presence of a compact source is correlated with the presence of extended radio emission and with the presence of optical emission lines.

Download Full-text

The Evolution of the Mass–Metallicity Relation in Seyferts

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310006058 ◽

2009 ◽

Vol 5 (S267) ◽

pp. 144-144

Author(s):

N. Vale Asari ◽

G. Stasińska ◽

R. Cid Fernandes ◽

J. M. Gomes ◽

M. Schlickmann ◽

...

Keyword(s):

Interstellar Medium ◽

Emission Line ◽

Empirical Relation ◽

Stellar Populations ◽

Stellar Mass ◽

Sloan Digital Sky Survey ◽

Emission Lines ◽

Chemical Enrichment ◽

Sky Survey ◽

History Of

Various studies have shown that there is an empirical relation between the nebular metallicity of a galaxy and its stellar mass. Until now, most studies of the mass-metallicity relation (M–Z) have focused on the abundances of the interstellar medium as measured by emission-line features. This technique thus excludes galaxies with AGN from the working samples, due to the difficulty to measure the nebular abundances when emission-lines are powered both by stars and AGN. With our synthesis code starlight, we are able to recover the stellar metallicities of galaxies from the Sloan Digital Sky Survey (SDSS). Therefore, although we still cannot measure the nebular metallicity in AGN hosts, we know their present-day stellar metallicities. Moreover, because we measure the metallicity of stellar populations of different ages in a galaxy, we are also able also recover the history of its chemical enrichment.

Download Full-text

Radio Morphology of Red Geysers

The Astrophysical Journal ◽

10.3847/1538-4357/ac24a0 ◽

2021 ◽

Vol 922 (2) ◽

pp. 230

Author(s):

Namrata Roy ◽

Emily Moravec ◽

Kevin Bundy ◽

Martin J. Hardcastle ◽

Gülay Gürkan ◽

...

Keyword(s):

Star Formation ◽

Interstellar Medium ◽

Large Scale ◽

Formation Rate ◽

Small Scale ◽

Radio Sources ◽

Spatially Resolved ◽

Radio Imaging ◽

Extended Radio ◽

Massive Halos

Abstract We present 150 MHz, 1.4 GHz, and 3 GHz radio imaging (LoTSS, FIRST, and VLASS) and spatially resolved ionized gas characteristics (SDSS IV-MaNGA) for 140 local (z < 0.1) early-type red geyser galaxies. These galaxies have a low star formation activity (with a star formation rate, SFR, ∼ 0.01 M ⊙ yr−1), but show unique extended patterns in spatially resolved emission-line maps that have been interpreted as large-scale ionized winds driven by active galactic nuclei (AGN). In this work, we confirm that red geysers host low-luminosity radio sources (L 1.4GHz ∼ 1022 WHz −1). Out of 42 radio-detected red geysers, 32 are spatially resolved in LoTSS and FIRST, with radio sizes varying between ∼5–25 kpc. Three sources have radio sizes exceeding 40 kpc. A majority display a compact radio morphology and are consistent with either low-power compact radio sources (FR0 galaxies) or radio-quiet quasars. They may be powered by small-scale AGN-driven jets that remain unresolved at the current 5″ resolution of radio data. The extended radio sources, not belonging to the “compact” morphological class, exhibit steeper spectra with a median spectral index of −0.67, indicating the dominance of lobed components. The red geysers hosting extended radio sources also have the lowest specific SFRs, suggesting they either have a greater impact on the surrounding interstellar medium or are found in more massive halos on average. The degree of alignment of the ionized wind cone and the extended radio features are either 0° or 90°, indicating possible interaction between the interstellar medium and the central radio AGN.

Download Full-text

Extended Emission-Line Regions Around AGN

International Astronomical Union Colloquium ◽

10.1017/s0252921100040288 ◽

1997 ◽

Vol 159 ◽

pp. 280-287

Author(s):

A. Robinson

Keyword(s):

Interstellar Medium ◽

Emission Line ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Active Galaxies ◽

Radio Sources ◽

Relative Importance ◽

High Excitation ◽

Ambient Gas ◽

Extended Emission

AbstractHigh-excitation extended emission-line nebulae around active galactic nuclei probably result either from photoionization of the interstellar medium by beamed continuum radiation, or dynamical interactions between radio sources and the ambient gas, or both. Here I discuss the models based on these mechanisms, and their relative importance in radio-quiet and radio-loud active galaxies.

Download Full-text