Constraints on the production and escape of ionizing radiation from the emission-lines of metal-poor star-forming galaxies

AbstractTo understand how the nature of the ionizing sources and the leakage of ionizing photons in high-redshift galaxies can be constrained from their emission-line spectra, we compare emission-line models of star-forming galaxies including leakage of ionizing radiation, active galactic nuclei (AGN) and radiative shocks, with observations of galaxies at various redshifts with properties expected to approach those of primeval galaxies.

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A bayesian-like approach to derive chemical abundances in type-2 active galactic nuclei based on photoionization models

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2278 ◽

2019 ◽

Vol 489 (2) ◽

pp. 2652-2668 ◽

Cited By ~ 6

Author(s):

E Pérez-Montero ◽

O L Dors ◽

J M Vílchez ◽

R García-Benito ◽

M V Cardaci ◽

...

Keyword(s):

Emission Line ◽

Active Galactic Nuclei ◽

Chemical Properties ◽

Galactic Nuclei ◽

Optical Emission ◽

Emission Lines ◽

Chemical Abundances ◽

Star Forming ◽

Large Dispersion

Abstract We present a new methodology for the analysis of the emission lines of the interstellar medium in the narrow-line regions around type-2 active galactic nuclei. Our aim is to provide a recipe that can be used for large samples of objects in a consistent way using different sets of optical emission lines that takes into the account possible variations from the O/H–N/O relation to use [N ii] lines. Our approach consists of a bayesian-like comparison between certain observed emission-line ratios sensitive to total oxygen abundance, nitrogen-to-oxygen ratio, and ionization parameter with the predictions from a large grid of photoionization models calculated under the most usual conditions in this environment. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes and determinations of their chemical properties from detailed models in the literature. Our results agree within the errors with other results and confirm the high metallicity of the objects of the sample, with N/O values consistent with a large secondary production of N, but with a large dispersion. The obtained ionization parameters for this sample are much larger than those for star-forming object at the same metallicity.

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Molecular hydrogen and [Fe ii] in active galactic nuclei – III. Low-ionization nuclear emission-line region and star-forming galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stt026 ◽

2013 ◽

Vol 430 (3) ◽

pp. 2002-2017 ◽

Cited By ~ 45

Author(s):

R. Riffel ◽

A. Rodríguez-Ardila ◽

I. Aleman ◽

M. S. Brotherton ◽

M. G. Pastoriza ◽

...

Keyword(s):

Emission Line ◽

Active Galactic Nuclei ◽

Molecular Hydrogen ◽

Galactic Nuclei ◽

Star Forming ◽

Line Region

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The Galactic center: not an active galactic nucleus

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314000131 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 54-58

Author(s):

Deokkeun An ◽

Solange V. Ramírez ◽

Kris Sellgren

Keyword(s):

Interstellar Medium ◽

Emission Line ◽

Active Galactic Nuclei ◽

Active Galactic Nucleus ◽

Galactic Center ◽

Galactic Nuclei ◽

Extensive Area ◽

Star Forming ◽

Nearby Galaxies

AbstractWe present 10 μm – 35μm Spitzer spectra of the interstellar medium in the central molecular zone (CMZ), the central 210 pc × 60 pc of the Galactic center (GC). We present maps of the CMZ in ionic and H2 emission, covering a more extensive area than earlier spectroscopic surveys in this region. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby Galaxies Survey to our data. Previous work shows that forbidden line ratios can distinguish star-forming galaxies from low-ionization nuclear emission-line regions (LINERs) and active galactic nuclei (AGNs). Our GC line ratios agree with star-forming galaxies and not with LINERs or AGNs.

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Optical spectroscopy of type 2 LINERs

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936680 ◽

2020 ◽

Vol 635 ◽

pp. A50

Author(s):

L. Hermosa Muñoz ◽

S. Cazzoli ◽

I. Márquez ◽

J. Masegosa

Keyword(s):

Emission Line ◽

Galactic Nuclei ◽

Emission Lines ◽

True Nature ◽

Star Forming ◽

Broad Component ◽

Line Region ◽

Line Fitting

Context. Type 2 Low-ionization Nuclear Emission-line Regions (LINERs) have been optically classified with the Palomar data as not presenting a broad component in the Balmer emission lines that are associated with the broad-line region (BLR) of the active galactic nuclei (AGN). Aims. We aim to unveil the presence of different kinematic components of emission lines in the nuclear region of a sample of local (z ≤ 0.022) type 2 LINERs. We focus on the analysis of the true nature of LINERs by means of the detection (or nondetection) of a broad component that originated in the BLR of the AGN. Additionally, we search for the possible presence of nonrotational motions such as outflows in these LINERs. Methods. We applied a decomposition of the nuclear emission lines using an spectroscopic analysis of the optical spectra of nine type 2 LINERs of intermediate-resolution spectroscopic data retrieved from the Hubble Space Telescope (HST) archive. The study is completed with archival spectra from the Double Spectrograph from the Palomar Observatory. Results. The emission line fitting reveals the presence of a broad component associated with the BLR in six out of the nine galaxies for the space-based data, and for two out of the eight from the ground-based spectra. The velocity dispersion for two galaxies (NGC 4486 and NGC 4594) measured in HST/STIS data suggest the presence of outflows. Conclusions. The results indicate that the spatial resolution plays a major role in the detection of the BLR, as it appears diluted in the ground-based data (even after removing stellar contribution). This is also true for the emission line diagnostics, as the contaminant light contributes to lower emission line ratios toward the star-forming area of standard BPTs. We propose to reclassify NGC 4594 as a type 1 LINER, since a BLR component is seen in both space- and ground-based spectra. We find ambiguous results for the BLR component of NGC 4486. The modest outflow detection in our sample may indicate that they are not as frequent as seen for type 1 LINERs.

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The MOSDEF-LRIS Survey: The Interplay Between Massive Stars and Ionized Gas in High-Redshift Star-Forming Galaxies1

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1410 ◽

2020 ◽

Cited By ~ 6

Author(s):

Michael W Topping ◽

Alice E Shapley ◽

Naveen A Reddy ◽

Ryan L Sanders ◽

Alison L Coil ◽

...

Keyword(s):

Emission Line ◽

High Redshift ◽

Optical Emission ◽

Continuum Emission ◽

Joint Analysis ◽

High Redshift Galaxies ◽

Star Forming ◽

Composite Spectra ◽

Local Sequence ◽

Ionization Parameter

Abstract We present a joint analysis of rest-UV and rest-optical spectra obtained using Keck/LRIS and Keck/MOSFIRE for a sample of 62 star-forming galaxies at z ∼ 2.3. We divide our sample into two bins based on their location in the [OIII]5007/Hβ vs. [NII]6584/Hα BPT diagram, and perform the first differential study of the rest-UV properties of massive ionizing stars as a function of rest-optical emission-line ratios. Fitting BPASS stellar population synthesis models, including nebular continuum emission, to our rest-UV composite spectra, we find that high-redshift galaxies offset towards higher [OIII]λ5007/Hβ and [NII]λ6584/Hα have younger ages ($\log (\textrm {~Age/yr})=7.20^{+0.57}_{-0.20}$) and lower stellar metallicities ($Z_*=0.0010^{+0.0011}_{-0.0003}$) resulting in a harder ionizing spectrum, compared to the galaxies in our sample that lie on the local BPT star-forming sequence ($\log (\textrm {Age/yr})=8.57^{+0.88}_{-0.84}$, $Z_*=0.0019^{+0.0006}_{-0.0006}$). Additionally, we find that the offset galaxies have an ionization parameter of $\log (U)=-3.04^{+0.06}_{-0.11}$ and nebular metallicity of ($12+\log (\textrm {~O/H})=8.40^{+0.06}_{-0.07}$), and the non-offset galaxies have an ionization parameter of $\log (U)=-3.11^{+0.08}_{-0.08}$ and nebular metallicity of $12+\log (\textrm {~O/H})=8.30^{+0.05}_{-0.06}$. The stellar and nebular metallicities derived for our sample imply that the galaxies offset from the local BPT relation are more α-enhanced ($7.28^{+2.52}_{-2.82}\textrm {~O/Fe}_{\odot }$) compared to those consistent with the local sequence ($3.04^{+0.95}_{-0.54}\textrm {~O/Fe}_{\odot }$). However, even galaxies that are entirely consistent with the local nebular excitation sequence appear to be α-enhanced – in contrast with typical local systems. Such differences must be considered when estimating gas-phase oxygen abundances at high redshift based on strong emission-line ratios. Specifically, a similarity in the location of high-redshift and local galaxies in the BPT diagram may not be indicative of a similarity in their physical properties.

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Constraints on the production and escape of ionizing radiation from the emission-line spectra of metal-poor star-forming galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2616 ◽

2019 ◽

Vol 490 (1) ◽

pp. 978-1009 ◽

Cited By ~ 13

Author(s):

A Plat ◽

S Charlot ◽

G Bruzual ◽

A Feltre ◽

A Vidal-García ◽

...

Keyword(s):

Ionizing Radiation ◽

Emission Line ◽

Binary Star ◽

Reference Sample ◽

Initial Mass Function ◽

Attractive Alternative ◽

Radiative Shock ◽

Star Forming ◽

Element Abundances ◽

Metal Poor Star

ABSTRACT We explore the production and escape of ionizing photons in young galaxies by investigating the ultraviolet and optical emission-line properties of models of ionization-bounded and density-bounded H ii regions, active-galactic-nucleus (AGN) narrow-line regions, and radiative shocks computed all using the same physically consistent description of element abundances and depletion on to dust grains down to very low metallicities. We compare these models with a reference sample of metal-poor star-forming galaxies and Lyman-continuum (LyC) leakers at various redshifts, which allows the simultaneous exploration of more spectral diagnostics than typically available at once for individual subsamples. We confirm that current single- and binary-star population synthesis models do not produce hard-enough radiation to account for the high-ionization emission of the most metal-poor galaxies. Introducing either an AGN or radiative-shock component brings models into agreement with observations. A published model including X-ray binaries is an attractive alternative to reproduce the observed rise in He iiλ4686/H β ratio with decreasing oxygen abundance in metal-poor star-forming galaxies, but not the high observed He iiλ4686/Hβ ratios of galaxies with large EW(Hβ). A source of harder ionizing radiation appears to be required in these extreme objects, such as an AGN or radiative-shock component, perhaps linked to an initial-mass-function bias towards massive stars at low metallicity. This would also account for the surprisingly high [O i]/[O iii] ratios of confirmed LyC leakers relative to ionization-bounded models. We find no simple by-eye diagnostic of the nature of ionizing sources and the escape of LyC photon, which require proper simultaneous fits of several lines to be discriminated against.

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THE PRESENCE OF WEAK ACTIVE GALACTIC NUCLEI IN HIGH REDSHIFT STAR-FORMING GALAXIES

The Astrophysical Journal ◽

10.1088/0004-637x/711/2/1291 ◽

2010 ◽

Vol 711 (2) ◽

pp. 1291-1296 ◽

Cited By ~ 45

Author(s):

Shelley A. Wright ◽

James E. Larkin ◽

James R. Graham ◽

Chung-Pei Ma

Keyword(s):

Active Galactic Nuclei ◽

High Redshift ◽

Galactic Nuclei ◽

Star Forming

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Outflows and extended [C ii] haloes in high-redshift galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1163 ◽

2020 ◽

Vol 495 (1) ◽

pp. 160-172 ◽

Cited By ~ 5

Author(s):

E Pizzati ◽

A Ferrara ◽

A Pallottini ◽

S Gallerani ◽

L Vallini ◽

...

Keyword(s):

High Redshift ◽

Galactic Nuclei ◽

Dark Matter Halo ◽

Additional Energy ◽

Dynamical Mass ◽

High Redshift Galaxies ◽

Star Forming ◽

Outflow Rate ◽

Pm 10 ◽

Η Value

ABSTRACT Recent stacked ALMA observations have revealed that normal, star-forming galaxies at z ≈ 6 are surrounded by extended (≈10 kpc) [C ii]-emitting haloes, which are not predicted by the most advanced, zoom-in simulations. We present a model in which these haloes are the result of supernova-driven cooling outflows. Our model contains two free parameters, the outflow mass loading factor, η, and the parent galaxy dark matter halo circular velocity, vc. The outflow model successfully matches the observed [C ii] surface brightness profile if η = 3.20 ± 0.10 and $v_{\rm c} = 170 \pm 10 \, \rm km\, s^{-1}$, corresponding to a dynamical mass of ${\approx }10^{11}\, {\rm M}_{\odot }$. The predicted outflow rate and velocity range are $128 \pm 5\, {\rm M}_{\odot }\, {\rm yr}^{-1}$ and 300–500 $\, \rm km\, s^{-1}$, respectively. We conclude that (a) extended haloes can be produced by cooling outflows; (b) the large η value is marginally consistent with starburst-driven outflows, but it might indicate additional energy input from active galactic nuclei; and (c) the presence of [C ii] haloes requires an ionizing photon escape fraction from galaxies fesc ≪ 1. The model can be readily applied also to individual high-z galaxies, as those observed, e.g. by the ALMA ALPINE survey now becoming available.

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Host galaxy properties of changing-look AGNs revealed in the MaNGA survey

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2627 ◽

2020 ◽

Vol 498 (3) ◽

pp. 3985-3994

Author(s):

Xiaoling Yu ◽

Yong Shi ◽

Yanmei Chen ◽

Jianhang Chen ◽

Songlin Li ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Main Sequence ◽

Galactic Nuclei ◽

Axial Ratio ◽

Emission Lines ◽

Host Galaxy ◽

Type I ◽

Host Galaxies ◽

Star Forming ◽

Nearby Galaxies

ABSTRACT Changing-look active galactic nuclei (CL-AGNs) are a subset of AGNs in which the broad Balmer emission lines appear or disappear within a few years. We use the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to identify five CL-AGNs. The 2D photometric and kinematic maps reveal common features as well as some unusual properties of CL-AGN hosts as compared to the AGN hosts in general. All MaNGA CL-AGNs reside in the star-forming main sequence, similar to MaNGA non-changing-look AGNs (NCL-AGNs). The $80 \pm 16{{\ \rm per\ cent}}$ of our CL-AGNs do possess pseudo-bulge features, and follow the overall NCL-AGN MBH–σ* relationship. The kinematic measurements indicate that they have similar distributions in the plane of angular momentum versus galaxy ellipticity. MaNGA CL-AGNs, however, show a higher, but not statistically significant ($20 \pm 16{{\ \rm per\ cent}}$) fraction of counter-rotating features compared to that ($1.84 \pm 0.61{{\ \rm per\ cent}}$) in general star formation population. In addition, MaNGA CL-AGNs favour more face-on (axial ratio > 0.7) than that of type I NCL-AGNs. These results suggest that host galaxies could play a role in the CL-AGN phenomenon.

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