scholarly journals 3.31. Tri-dimensional observation of the superbubble in the starburst galaxy NGC 2782

1998 ◽  
Vol 184 ◽  
pp. 151-152
Author(s):  
M. Yoshida
Keyword(s):  
Spatial Distribution ◽  
Emission Line ◽  
Emission Lines ◽  
Starburst Galaxy ◽  
Two Dimensional ◽  
Excitation Mechanism ◽  
Ionized Gas ◽  
Shock Heating

We present results of an optical tri-dimensional observation of the central 2′ × 12″ region of the starburst galaxy NGC 2782. The circumnuclear Hα emission lines consist of broad (δv ~ 300 km s−1), blue-shifted component and narrow (δv < 100 km s−1) component and we first revealed the two-dimensional spatial distribution of those two components. The broad Hα emitting region is extended to 6″ (> 1 kpc) south from the nucleus and the emission-line ratios indicates that shock heating may be the main excitation mechanism of the ionized gas in the region. We conclude that this region is a superbubble outflowing from the nuclear starburst region.

scholarly journals The Shocking Truth About some “Proto-PN”

1989 ◽  
Vol 131 ◽  
pp. 447-447
Author(s):  
R. W. Goodrich ◽  
Luciana Bianchi
Keyword(s):  
Emission Lines ◽  
Excitation Mechanism ◽  
Strong Emission ◽  
Shock Heating ◽  
Central Stars

A small number of bipolar planetaries -including M2-9, M1-91, GL 618, and M2-56- exhibit very strong emission lines of low ionization species such as [O I], [N I], [N II], and [S II]. Most previous authors have attempted to analyze the spectra of these objects assuming that they are photoionized by their central stars. Closer examination, however, suggests that a different excitation mechanism may be at work -that of shock heating.

scholarly journals Deciphering the Origin of Ionized Gas in IC 1459 with VLT/MUSE

2021 ◽  
Author(s):  
C R Mulcahey ◽  
L J Prichard ◽  
D Krajnović ◽  
R A Jorgenson
Keyword(s):  
Emission Line ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Ionized Gas ◽  
Shock Heating ◽  
Very Large Telescope ◽  
Stellar Component ◽  
Group Environment ◽  
Stellar Properties ◽  
Field Unit

Abstract IC 1459 is an early-type galaxy (ETG) with a rapidly counter-rotating stellar core, and is the central galaxy in a gas-rich group of spirals. In this work, we investigate the abundant ionized gas in IC 1459 and present new stellar orbital models to connect its complex array of observed properties and build a more complete picture of its evolution. Using the Multi-Unit Spectroscopic Explorer (MUSE), the optical integral field unit (IFU) on the Very Large Telescope (VLT), we examine the gas and stellar properties of IC 1459 to decipher the origin and powering mechanism of the galaxy’s ionized gas. We detect ionized gas in a non-disk-like structure rotating in the opposite sense to the central stars. Using emission-line flux ratios and velocity dispersion from full-spectral fitting, we find two kinematically distinct regions of shocked emission-line gas in IC 1459, which we distinguished using narrow (σ ≤ 155 km s−1) and broad (σ &gt; 155 km s−1) profiles. Our results imply that the emission-line gas in IC 1459 has a different origin than that of its counter-rotating stellar component. We propose that the ionized gas is from late-stage accretion of gas from the group environment, which occurred long after the formation of the central stellar component. We find that shock heating and AGN activity are both ionizing mechanisms in IC 1459 but that the dominant excitation mechanism is by post-asymptotic giant branch stars from its old stellar population.

scholarly journals Understanding Galaxy Evolution Through Emission Lines

2019 ◽  
Vol 57 (1) ◽  
pp. 511-570 ◽  
Author(s):  
Lisa J. Kewley ◽  
David C. Nicholls ◽  
Ralph S. Sutherland
Keyword(s):  
Emission Line ◽  
Galaxy Evolution ◽  
Sample Selection ◽  
Cosmic Time ◽  
Emission Lines ◽  
Ionized Gas ◽  
Fundamental Properties ◽  
Integral Field Spectroscopy ◽  
Diffuse Ionized Gas ◽  
Ionization Parameter

We review the use of emission lines for understanding galaxy evolution, focusing on excitation source, metallicity, ionization parameter, ISM pressure, and electron density. We discuss the physics, benefits, and caveats of emission line diagnostics, including the effects of theoretical model uncertainties, diffuse ionized gas, and sample selection bias. In anticipation of upcoming telescope facilities, we provide new self-consistent emission line diagnostic calibrations for complete spectral coverage from the UV to the IR. These diagnostics can be used in concert to understand how fundamental galaxy properties have changed across cosmic time. We conclude the following: ▪ The UV, optical, and IR contain complementary diagnostics that can probe the conditions within different nebular ionization zones. ▪ Accounting for complex density gradients and temperature profiles is critical for reliably estimating the fundamental properties of Hii regions and galaxies. ▪ Diffuse ionized gas can raise metallicity estimates, flatten metallicity gradients, and introduce scatter in ionization parameter measurements. ▪ New 3D emission line diagnostics successfully separate the contributions from star formation, AGN, and shocks using integral field spectroscopy. We summarize with a discussion of the challenges and major opportunities for emission line diagnostics in the coming years.

scholarly journals Deep Spectroscopy of the Very Extended Ionized Gas of NGC 4388

2004 ◽  
Vol 217 ◽  
pp. 386-388
Author(s):  
Michitoshi Yoshida ◽  
M. Yagi ◽  
S. Okamura ◽  
Y. Ohyama ◽  
N. Kashikawa ◽  
...  
Keyword(s):  
Emission Line ◽  
Virgo Cluster ◽  
Ionized Gas ◽  
Shock Heating ◽  
Line Region ◽  
Systemic Velocity ◽  
Ram Pressure ◽  
The Galaxy ◽  
Solar Abundances ◽  
Extended Emission

We report here the results of deep optical spectroscopy of the very extended emission-line region (VEELR) found serendipitously around the Seyfert 2 galaxy NGC 4388 in the Virgo cluster. The Hα recession velocities of most of the filaments of the region observed are highly blue-shifted with respect to the systemic velocity of the galaxy. The velocity field is complicated, and there seem to be several streams of filaments ranging from ~ −100 km s−1 to ~ −700 km s−1 with respect to the systemic velocity of the galaxy. The emission-line ratios of the VEELR filaments are well explained by power-law photoionization models with solar abundances. In addition to photoionization, shock heating probably contributes to the ionization of the gas. We conclude that the VEELR was formerly the disk gas of NGC 4388, which has been stripped by ram pressure due to the interaction between the hot intra-cluster medium (ICM) and the galaxy.

scholarly journals Excitation Mechanism of Extended Emission-Line Regions in Active Galaxies

1997 ◽  
Vol 159 ◽  
pp. 386-389
Author(s):  
Ian Evans ◽  
Anuradha Koratkar ◽  
Mark Allen ◽  
Zlatan Tsvetanov ◽  
Michael Dopita
Keyword(s):  
Emission Line ◽  
Hubble Space Telescope ◽  
Optical Emission ◽  
Active Galaxies ◽  
Emission Lines ◽  
Uv Spectrophotometry ◽  
Excitation Mechanism ◽  
Space Telescope ◽  
Shock Models ◽  
Extended Emission

AbstractPhotoionization and shock models of the extended emissionline regions (EELRs) in active galaxies demonstrate that the optical emission lines alone are a poor discriminant of the excitation mechanism. Combining optical and UV data provides a discriminant between nuclear photoionization and autoionizing shock models. Hubble Space Telescope UV spectrophotometry of two Seyferts suggests that the EELRs in these objects are probably photoionized by the nucleus.

scholarly journals Physical Conditions in Radio Galaxies and Quasars

1977 ◽  
Vol 74 ◽  
pp. 183-191
Author(s):  
Donald E. Osterbrock
Keyword(s):  
Emission Line ◽  
Large Fraction ◽  
Radio Galaxies ◽  
Emission Lines ◽  
Ionized Gas ◽  
Strong Emission ◽  
Normal Galaxies ◽  
Physical Conditions ◽  
Early Survey ◽  
Optical Identifications

It is well known from the pioneering work of Baade and Minkowski that radio galaxies very often have strong emission lines in the spectra of their nuclei, indicating the presence of relatively large amounts of ionized gas. For instance, in the early survey of radio galaxies by Schmidt (1965), of the 35 galaxies observed, 32 had at least [0 II] λ3727 in their spectra and well over half had relatively strong [0 II] and other observable emission lines as well. In the recent review of optical identifications and spectroscopy of the revised 3C catalogue of radio sources by Smith et al. (1976), 137 radio galaxies are listed. Of these descriptive spectral information is given for 98, of which 49 show strong–emission line spectra, 19 intermediate–strength emission, 12 weak emission, and 18 a pure absorption–line spectrum without detectable emission lines. The fraction of objects with emission line–spectra is much higher than for normal galaxies. It is thus apparent that though the presence of emission lines is neither a necessary nor a sufficient condition that a galaxy be an observable radio source, nevertheless a large fraction of radio galaxies do contain ionized gas in their nuclei.

scholarly journals Gaia-assisted discovery of a detached low-ionisation BAL quasar with very large ejection velocities

2020 ◽  
Vol 634 ◽  
pp. A111 ◽  
Author(s):  
J. P. U. Fynbo ◽  
P. Møller ◽  
K. E. Heintz ◽  
J. N. Burchett ◽  
L. Christensen ◽  
...  
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Emission Lines ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Red Edge ◽  
First Case ◽  
Bl Lac ◽  
Spatially Extended ◽  
Extended Emission

We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Si IV, C IV, and Al III, a redshift of z = 2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 Å that is most likely due to Lyman-α emission, which implies a systemic redshift of z = 2.66 if correctly identified. There is also evidence for the onset of Lyman-α forest absorption bluewards of 4450 Å and evidence for Hα emission in the K band consistent with a systemic redshift of z = 2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s−1 to 40 000 km s−1. To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-α emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.

scholarly journals The SAMI Galaxy Survey: reconciling strong emission line metallicity diagnostics using metallicity gradients

2021 ◽  
Vol 502 (3) ◽  
pp. 3357-3373
Author(s):  
Henry Poetrodjojo ◽  
Brent Groves ◽  
Lisa J Kewley ◽  
Sarah M Sweet ◽  
Sebastian F Sanchez ◽  
...  
Keyword(s):  
Emission Line ◽  
Electron Temperature ◽  
Gas Phase ◽  
Mass Range ◽  
Accurate Method ◽  
Emission Lines ◽  
Mass Relation ◽  
Strong Emission ◽  
Data Release ◽  
Accurate Comparison

ABSTRACT We measure the gas-phase metallicity gradients of 248 galaxies selected from Data Release 2 of the SAMI Galaxy Survey. We demonstrate that there are large systematic discrepancies between the metallicity gradients derived using common strong emission line metallicity diagnostics. We determine which pairs of diagnostics have Spearman’s rank coefficients greater than 0.6 and provide linear conversions to allow the accurate comparison of metallicity gradients derived using different strong emission line diagnostics. For galaxies within the mass range 8.5 &lt; log (M/M⊙) &lt; 11.0, we find discrepancies of up to 0.11 dex/Re between seven popular diagnostics in the metallicity gradient–mass relation. We find a suggestion of a break in the metallicity gradient–mass relation, where the slope shifts from negative to positive, occurs between 9.5 &lt; log (M/M⊙) &lt; 10.5 for the seven chosen diagnostics. Applying our conversions to the metallicity gradient–mass relation, we reduce the maximum dispersion from 0.11 dex/Re to 0.02 dex/Re. These conversions provide the most accurate method of converting metallicity gradients when key emission lines are unavailable. We find that diagnostics that share common sets of emission line ratios agree best, and that diagnostics calibrated through the electron temperature provide more consistent results compared to those calibrated through photoionization models.

Ionized gas kinematics and luminosity profiles of Low-z Lyman Alpha Blobs

2019 ◽  
Vol 15 (S359) ◽  
pp. 413-414
Author(s):  
María P. Agüero ◽  
Rubén Díaz ◽  
Mischa Schirmer
Keyword(s):  
Emission Line ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Lyman Alpha ◽  
Gas Kinematics ◽  
The Universe ◽  
Very High ◽  
The Continuum

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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