The ionization mechanism of NGC 185: how to fake a Seyfert galaxy?★

Martins, Lucimara P.; Lanfranchi, Gustavo A.; Gonçalves, Denise R.; Magrini, L.; Teodorescu, A. M.; Quireza, C.

doi:10.1111/j.1365-2966.2011.19954.x

Cited by 7 publications

(20 citation statements)

References 41 publications

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“…With an upper limit of 0.06 mJy at 21 cm (Lucero & Young 2007) and the absence of emission‐lines characteristic for low‐ionization nuclear emission‐line region (LINER) or Seyfert galaxies (Martins et al 2012), the JCMT 1.1 mm flux measured by Fich & Hodge (1991) is unlikely to be caused by synchrotron emission from either supernova remnants (SNRs) or an active galactic nucleus (AGN) like nucleus. Also the contribution from CO (2–1) line emission seems unable to account for the high mm measurement.…”

Section: Resultsmentioning

confidence: 99%

Herschel^★and JCMT observations of the early-type dwarf galaxy NGC 205

Looze

Baes

Parkin

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We present Herschel dust continuum, James Clerk Maxwell Telescope CO (3–2) observations and a search for [C ii] 158 m and [O i] 63 m spectral line emission for the brightest early‐type dwarf satellite of Andromeda, NGC 205. While direct gas measurements [Mg∼ 1.5 × 106 M⊙, H i+ CO (1–0)] have proven to be inconsistent with theoretical predictions of the current gas reservoir in NGC 205 (>107 M⊙), we revise the missing interstellar medium mass problem based on new gas mass estimates (CO (3–2), [C ii], [O i]) and indirect measurements of the interstellar medium content through dust continuum emission. Based on Herschel observations, covering a wide wavelength range from 70 to 500 m, we are able to probe the entire dust content in NGC 205 ( M⊙ at Td∼ 18–22 K) and rule out the presence of a massive cold dust component ( M⊙, Td∼ 12 K), which was suggested based on millimetre observations from the inner 18.4 arcsec. Assuming a reasonable gas‐to‐dust ratio of ∼400, the dust mass in NGC 205 translates into a gas mass Mg∼ 4–7 × 106 M⊙. The non‐detection of [O i] and the low L[C II]‐to‐LCO(1‐0) line intensity ratio (∼1850) imply that the molecular gas phase is well traced by CO molecules in NGC 205. We estimate an atomic gas mass of 1.5 × 104 M⊙ associated with the [C ii] emitting photodissociation regions in NGC 205. From the partial CO (3–2) map of the northern region in NGC 205, we derive a molecular gas mass of M⊙. Upon comparison with the molecular gas mass estimated from CO (1–0) observations ( M⊙), we find most of the H2 gas in NGC 205 to be locked in diffuse regions of low density and/or temperature, characteristic for an interstellar medium with little star formation activity. New total gas mass estimates from Herschel dust continuum (4–7 × 106 M⊙), Herschel [C ii] line spectroscopic mapping (1.5 × 104 M⊙) and James Clerk Maxwell Telescope CO (3–2) observations (7 × 105 M⊙), including the H i mass ( M⊙) and a correction for heavier elements, confirm the deficiency of the interstellar medium (gas+dust) in the inner regions of NGC 205, which is predicted to contain at least >107 M⊙ of gas if we assume a reasonable star formation efficiency of 10 per cent and account for the mass return from planetary nebulae. In an attempt to explain the missing interstellar medium mass problem, we claim that efficient supernova feedback capable of expelling gas from the inner, star‐forming regions to the outer regions and/or tidal interactions with M31 stripping the gas component from the galaxy provide the best explanation for the removal of a significant amount of gas and dust from NGC 205.

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Section: Resultsmentioning

confidence: 99%

Herschel^★and JCMT observations of the early-type dwarf galaxy NGC 205

Looze

Baes

Parkin

et al. 2012

Monthly Notices of the Royal Astronomical Society

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“…Given the lack of radio evidence for the presence of an AGN in these galaxies, we conclude that the most likely explanation for the origin of the Seyfert-like emission line properties in NGC3156, NGC3182, NGC3599, and NGC4324 is stellar processes. For example, photoionization driven by supernova remnants and/or planetary nebulae has been known to mimic the high-ionization nebular emission characteristic of Seyfert nuclei (e.g., Martins et al 2012). The poststarburst features in the optical spectrum of NGC3156 support this scenario (Caldwell et al 1996;Sarzi et al 2010).…”

Section: The Nuclear Radio Emission Connectionmentioning

confidence: 99%

“…It is also possible that the criteria we used to identify Seyfert nuclei in our ETG sample are unreliable or insufficient in these systems. If this is indeed the case, the high ionization nebular emission in the ETGs in the Seyfert class lacking nuclear radio emission may arise from stellar processes rather than SMBH accretion (e.g., Martins et al 2012). The situation is similar for ETGs in the LINER-AGN or LINER classes that lack 5 GHz detections.…”

Section: The Nuclear Radio Emission Connectionmentioning

confidence: 99%

The atlas^3DProject – XXXI. Nuclear radio emission in nearby early-type galaxies

Nyland¹,

Young²,

Wrobel³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present the results of a high-resolution, 5 GHz, Karl G. Jansky Very Large Array study of the nuclear radio emission in a representative subset of the ATLAS 3D survey of early-type galaxies (ETGs). We find that 51 ± 4% of the ETGs in our sample contain nuclear radio emission with luminosities as low as 10 18 W Hz −1 . Most of the nuclear radio sources have compact ( 25 − 110 pc) morphologies, although ∼10% display multi-component core+jet or extended jet/lobe structures. Based on the radio continuum properties, as well as optical emission line diagnostics and the nuclear X-ray properties, we conclude that the majority of the central 5 GHz sources detected in the ATLAS 3D galaxies are associated with the presence of an active galactic nucleus (AGN). However, even at sub-arcsecond spatial resolution, the nuclear radio emission in some cases appears to arise from low-level nuclear star formation rather than an AGN, particularly when molecular gas and a young central stellar population is present. This is in contrast to popular assumptions in the literature that the presence of a compact, unresolved, nuclear radio continuum source universally signifies the presence of an AGN. Additionally, we examine the relationships between the 5 GHz luminosity and various galaxy properties including the molecular gas mass and -for the first time -the global kinematic state. We discuss implications for the growth, triggering, and fueling of radio AGNs, as well as AGN-driven feedback in the continued evolution of nearby ETGs.

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“…Although there are still controversies on individual objects (e.g. Martins et al 2012, who found a galaxy with no signs of activity but whose line ratios put it as a Seyfert galaxy), these diagrams can be used with great confidence to study the nature of the central source that powers the observed emission lines.…”

Section: A P P E N D I X B : E M I S S I O N L I N E F L U X E Smentioning

confidence: 99%

Probing evolutionary population synthesis models in the near infrared with early-type galaxies

Dahmer-Hahn

Riffel

Rodríguez-Ardila

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We performed a near-infrared (NIR; ∼1.0 -2.4 µm) stellar population study in a sample of early-type galaxies. The synthesis was performed using five different evolutionary population synthesis libraries of models. Our main results can be summarized as follows: low-spectral-resolution libraries are not able to produce reliable results when applied to the NIR alone, with each library finding a different dominant population. The two newest higher resolution models, on the other hand, perform considerably better, finding consistent results to each other and to literature values. We also found that optical results are consistent with each other even for lower resolution models. We also compared optical and NIR results and found out that lower resolution models tend to disagree in the optical and in the NIR, with higher fraction of young populations in the NIR and dust extinction ∼1 mag higher than optical values. For higher resolution models, optical and NIR results tend to agree much better, suggesting that a higher spectral resolution is fundamental to improve the quality of the results.

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The ionization mechanism of NGC 185: how to fake a Seyfert galaxy?★

Cited by 7 publications

References 41 publications

Herschel^★and JCMT observations of the early-type dwarf galaxy NGC 205

Herschel^★and JCMT observations of the early-type dwarf galaxy NGC 205

The atlas^3DProject – XXXI. Nuclear radio emission in nearby early-type galaxies

Probing evolutionary population synthesis models in the near infrared with early-type galaxies

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The ionization mechanism of NGC 185: how to fake a Seyfert galaxy?★

Cited by 7 publications

References 41 publications

Herschel★and JCMT observations of the early-type dwarf galaxy NGC 205

Herschel★and JCMT observations of the early-type dwarf galaxy NGC 205

The atlas3DProject – XXXI. Nuclear radio emission in nearby early-type galaxies

Probing evolutionary population synthesis models in the near infrared with early-type galaxies

Contact Info

Product

Resources

About

Herschel^★and JCMT observations of the early-type dwarf galaxy NGC 205

Herschel^★and JCMT observations of the early-type dwarf galaxy NGC 205

The atlas^3DProject – XXXI. Nuclear radio emission in nearby early-type galaxies