Strongly star forming galaxies in the local Universe with nebular He <scp>ii</scp>λ4686 emission

Shirazi, Maryam; Brinchmann, Jarle

doi:10.1111/j.1365-2966.2012.20439.x

Cited by 204 publications

(345 citation statements)

References 67 publications

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“…In fact, a large fraction of galaxies with oxygen abundances lower than 12 + log(O/H) = 8.2 do not show WR features (Guseva et al 2000;Brinchmann et al 2008;Shirazi & Brinchmann 2012). It is also known that in several H ii/BCDs (e.g., II Zw 70 and Mrk 178; Kehrig et al 2008Kehrig et al , 2013 He ii λ4686 emission does not strictly coincide with the location of the WR bumps.…”

Section: The He II λ4686 Emission Linementioning

confidence: 99%

On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies

Lagos

Papaderos

Gomes

et al. 2014

A&A

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Aims. The main goal of this study is to carry out a spatially resolved investigation of the warm interstellar medium (ISM) in the extremely metal-poor blue compact dwarf (BCD) galaxy HS 2236+1344. Special emphasis is laid on analysis of the spatial distribution of chemical abundances, emission-line ratios, and the kinematics of the ISM, and to the recent star-forming (SF) activity in this galaxy. Methods. This study is based on optical integral field unit spectroscopy data from Gemini Multi-Object Spectrograph (GMOS) at the Gemini North telescope and archival Sloan Digital Sky Survey (SDSS) images. The galaxy was observed at medium spectral resolution over the spectral range from ∼4300 Å to 7300 Å. The data were obtained in two different positions across the galaxy, obtaining a total 4 × 8 field that encompasses most of its ISM.Results. Emission-line maps and broad-band images obtained in this study indicate that HS 2236+1344 hosts three giant H ii regions (GH iiRs). Our data also reveal some faint curved features in the BCD periphery that might be due to tidal perturbations or expanding ionized-gas shells. The ISM velocity field shows systematic gradients along the major axis of the BCD, with its southeastern and northwestern half differing by ∼80 km s −1 in their recessional velocity over the field of view. The Hα and Hβ equivalent-width distribution in the central part of HS 2236+1344 is consistent with a very young (∼3 Myr) burst. Our surface photometry analysis reveals an underlying low surface brightness component with moderately red colors, which suggest that the galaxy has undergone previous star formation. We derive an integrated oxygen abundance of 12 + log(O/H) = 7.53 ± 0.06 and a nitrogen-to-oxygen ratio of log(N/O) = −1.57 ± 0.19. Our results are consistent, within the uncertainties, with a homogeneous distribution of oxygen and nitrogen within the ISM of the galaxy. The high-ionization He ii λ4686 emission line is detected only in the central part of HS 2236+1344. Similar to many BCDs with He ii λ4686 emission, HS 2236+1344 shows no Wolf-Rayet (WR) bump.

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Section: The He II λ4686 Emission Linementioning

confidence: 99%

On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies

Lagos

Papaderos

Gomes

et al. 2014

A&A

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“…J1622 is detected in the radio at 1.4 GHz from the FIRST survey, having a radio luminosity L 1.4GHz = 10 38.6 erg s −1 , corroborating strong star formation. More intriguingly, the galaxy shows strong Heλ4686Å (Shirazi & Brinchmann 2012) emission, which is a good tracer of stellar outflows from massive stars and particularly WolfRayet stars. This implies that strong contribution from stellar winds may be affecting the measured kinematics.…”

Section: B5 J162233+395650mentioning

confidence: 99%

Unravelling the Complex Structure of Agn-Driven Outflows. Ii. Photoionization and Energetics

Karouzos

Woo

Bae

2016

ApJ

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Outflows have been shown to be prevalent in galaxies hosting luminous active galactic nuclei (AGNs) and present a physically plausible way to couple the AGN energy output with the interstellar medium of their hosts. Despite their prevalence, accurate characterization of these outflows has been challenging. In the second of a series of papers, we use Gemini Multi-Object Spectrograph IFU data of 6 local (z< 0.1) and moderate-luminosity Type 2 AGNs to study the ionization properties and energetics of AGN-driven outflows. We find strong evidence that connect the extreme kinematics of the ionized gas with the AGN photoionization. The kinematic component related to the AGN-driven outflow is clearly separated from other kinematic components, such as virial motions or rotation, on the velocity and velocity dispersion diagram. Our spatially resolved kinematic analysis reveals that from 30% up to 90% of the total mass and kinetic energy of the outflow is contained within the central kpc of the galaxy. The spatially integrated mass and kinetic energy of the gas entrained in the outflow correlates well with the AGN bolometric luminosity and results in energy conversion efficiencies between 0.01% and 1%. Intriguingly, we detect ubiquitous signs of ongoing circumnuclear star formation. Their small size, the centrally contained mass and energy, and the universally detected circumnuclear star formation cast doubts on the potency of these AGN-driven outflows as agents of galaxy-scale negative feedback.

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“…Below z=0.5, the traditional BPT diagnostic ratios (Baldwin et al 1981;Veilleux & Osterbrock 1987), [N II]λ6584/Hα versus [O III]λ5007/Hβ, trace the ionization potential and are thus effective at separating narrow-lined AGNsfrom star-forming galaxies; tens of thousands of such obscured AGNs have been classified by SDSS with this method (e.g., Kauffmann et al 2003;Kewley et al 2006). Recently, He II λ4686/Hβ versus [N II] λ6584/Hα was introduced as an empirical diagnostic to separate starforming galaxies from AGNs (Shirazi & Brinchmann 2012).…”

Section: Identifying Type 2 Agnsmentioning

confidence: 99%

On R − W1 as a Diagnostic to Discover Obscured Active Galactic Nuclei in Wide-Area X-Ray Surveys

LaMassa

Civano

Brusa

et al. 2016

ApJ

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Capitalizing on the all-sky coverage of WISEand the 35% and 50% sky coverage from Sloan Digital Sky Survey and Pan-STARRS, respectively, we explore the efficacy of-, as a color diagnostic to identify obscured supermassive black hole accretion in wide-area X-ray surveys. We use the ∼16.5 deg 2 Stripe 82 X-ray survey data as a testbed to compare R W1 -with R−K, an oft-used obscured active galactic nucleus (AGN) selection criterion, and examine where different classes of objects lie in this parameter space. Most stars follow a well-defined path in R−K versus R W1space. We demonstrate that optically normal galaxies hosting X-ray AGNs at redshifts z 0.5 1 < < can be recovered with an R W1 4 -> colorcut, while they typically are not selected as AGNs based on their W W 1 2 -colors. Additionally, different observed X-ray luminosity bins favor different regions in R W1 -parameter space: moderate-luminosity AGNs > -erg s −1 ) have bluer colors; higher spectroscopic completeness of the Stripe 82X sample is needed to determine whether this is a selection effect or an intrinsic property. Finally, we parameterize X-ray obscuration of Stripe 82X AGNs by calculating their hardness ratios (HRs) and find no clear trends between HR and optical reddening. Our results will help inform best-effort practices in followingup obscured AGN candidates in current and future wide-area, shallow X-ray surveys, including the all-sky eROSITA mission.

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Strongly star forming galaxies in the local Universe with nebular He iiλ4686 emission

Cited by 204 publications

References 67 publications

On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies

On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies

Unravelling the Complex Structure of Agn-Driven Outflows. Ii. Photoionization and Energetics

On R − W1 as a Diagnostic to Discover Obscured Active Galactic Nuclei in Wide-Area X-Ray Surveys

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