On the Recent Discovery of Coronal [Fe x]λ6374 Emission in the Low-metallicity Dwarf Galaxy SDSS J0944-0038

Herenz, Edmund Christian; Micheva, Genoveva; Weilbacher, Peter M.; Monreal-Ibero, A.; Hayes, Matthew; Anders, F.; Rivinius, Thomas

doi:10.3847/2515-5172/acd69e

Cited by 4 publications

(1 citation statement)

References 7 publications

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“…The detection of very high-ionization emission lines could be an alternative channel to identify hidden AGN activity in dwarf galaxies, especially in the JWST era with restframe IR coverage (e.g., Cann et al 2018). However, here we want to highlight that it can be easy to misidentify [Fe X] λ6374 and Si II λ6371 (see also Herenz et al 2023).…”

Section: The Importance Of Optical Coronal Linesmentioning

confidence: 99%

CLASSY. VIII. Exploring the Source of Ionization with UV Interstellar Medium Diagnostics in Local High-z Analogs*

Mingozzi,

James,

Berg

et al. 2024

ApJ

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In the current JWST era, rest-frame UV spectra play a crucial role in enhancing our understanding of the interstellar medium (ISM) and stellar properties of the first galaxies in the epoch of reionization (z > 6). Here, we compare well-known and reliable optical diagrams sensitive to the main ionization source (i.e., star formation, SF; active galactic nuclei, AGN; and shocks) to UV counterparts proposed in the literature—the so-called “UV–BPT diagrams”—using the HST COS Legacy Archive Spectroscopic SurveY (CLASSY), which is the largest high-quality, high-resolution, and broad-wavelength range atlas of far-UV spectra for 45 local star-forming galaxies. In particular, we explore where CLASSY UV line ratios are located in the different UV diagnostic plots, taking into account state-of-the-art photoionization and shock models, and, for the first time, the measured ISM and stellar properties (e.g., gas-phase metallicity, ionization parameter, carbon abundance, and stellar age). We find that the combination of C iii] λ λ1907,9 He ii λ1640 and O iii] λ1666 can be a powerful tool to separate between SF, shocks, and AGN at subsolar metallicities. We also confirm that alternative diagrams without O iii] λ1666 still allow us to define an SF-locus, with some caveats. Diagrams including C iv λ λ1548,51 should be taken with caution given the complexity of this doublet profile. Finally, we present a discussion detailing the ISM conditions required to detect UV emission lines, visible only in low gas-phase metallicity (12 + log(O/H) ≲ 8.3) and high ionization parameter (log(U) ≳ −2.5) environments. Overall, CLASSY and our UV toolkit will be crucial in interpreting the spectra of the earliest galaxies that JWST is currently revealing.

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Section: The Importance Of Optical Coronal Linesmentioning

confidence: 99%

CLASSY. VIII. Exploring the Source of Ionization with UV Interstellar Medium Diagnostics in Local High-z Analogs*

Mingozzi,

James,

Berg

et al. 2024

ApJ

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Spatially resolved spectroscopic observations of gas emission in dwarf galaxies hosting accreting black hole candidate

Heckler,

Riffel,

Ricci

2024

Monthly Notices of the Royal Astronomical Society

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Recent studies on dwarf galaxies reveal that some of them harbor a massive black hole (BH), which is believed to have a similar mass of the Supermassive BH ‘seeds’ at early times. The origin and growth of the primitive BHs are still open questions, since these BH seeds are hardly observed at high redshifts. Therefore, massive BH of dwarf galaxies can be the perfect candidates to untangle BH ‘seeds’ properties and their influence on their host galaxy evolution, since massive BH may preserve their initial conditions due to its quiet merger and accretion histories. We use optical integral field unit observations, obtained with the Gemini GMOS-IFU, to study the gas emission and kinematics in four dwarf galaxies, candidates to host massive BH, based on the analysis of their [Fe x] luminosities measured from SDSS spectra. The [Fe x] emission line is not detected in our GMOS in any of the galaxies, prompting speculation that its absence in our recent data may stem from a past tidal disruption event coinciding with the observation period of the SDSS data. All galaxies exhibit extended gas emissions, and the spatially resolved emission-line ratio diagnostic diagrams present values that suggest AGN photoionization from the [S ii] – BPT diagram. The gas velocity fields of all galaxies are indicative of disturbed rotation patterns, with no detection of gas outflows in any of the sources. Although the [S ii] – BPT diagrams indicate AGN photoionization, further confirmation through multi-wavelength observations is required to validate this scenario.

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Active Dwarf Galaxy Database. I. Overlap between Active Galactic Nuclei Selected by Different Techniques

Wasleske,

Baldassare

2024

ApJ

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We assemble a sample of 733 dwarf galaxies (M * ≤ 109.5 M ⊙) with signatures of active galactic nuclei (AGN) and explore the intersection between different AGN-selection techniques. Objects in our database are compiled from previous studies that identify AGN in dwarf galaxies through spectroscopy, X-ray emission, infrared colors, and optical photometric variability. We apply a uniform set of AGN diagnostic tools to the database using archival data. We find that any single selection method captures no more than half of the overall AGN population, and there is a general disagreement among the AGN-selection methods in this stellar-mass regime. The largest overlap between methods is found when both methods use optical spectroscopic data. In contrast, the populations of AGN intersect the least when comparing those methods that use photometric data at different wavelengths. These results can be used to better constrain the active fraction in dwarf galaxies, which is in turn an important constraint for black hole seed formation models. In a follow-up paper, we will explore links between the effectiveness of each selection technique and host galaxy properties.

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On the Recent Discovery of Coronal [Fe x]λ6374 Emission in the Low-metallicity Dwarf Galaxy SDSS J0944-0038

Cited by 4 publications

References 7 publications

CLASSY. VIII. Exploring the Source of Ionization with UV Interstellar Medium Diagnostics in Local High-z Analogs*

CLASSY. VIII. Exploring the Source of Ionization with UV Interstellar Medium Diagnostics in Local High-z Analogs*

Spatially resolved spectroscopic observations of gas emission in dwarf galaxies hosting accreting black hole candidate

Active Dwarf Galaxy Database. I. Overlap between Active Galactic Nuclei Selected by Different Techniques

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