Polycyclic aromatic hydrocarbons in Seyfert and star-forming galaxies

García-Bernete, I.; Rigopoulou, D.; Alonso‐Herrero, A.; Pereira-Santaella, M.; Roche, P. F.; Kerkeni, Boutheı̈na

doi:10.1093/mnras/stab3127

Cited by 36 publications

(29 citation statements)

References 115 publications

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“…This is in agreement with the literature since the 6 µm feature is likely excited by SF-related emission, while the feature at the longer wavelength could be more affected by the presence of AGN, whose dust-reprocessed emission peaks in the 10-30 µm regime (e.g., Mullaney et al 2011). The depleted PAH luminosity in the presence of nuclear activity is consistent with the recent results from García-Bernete et al (2022), who observed depleted PAH emission in the nuclear region of local AGN and found that AGNdominated objects show PAH luminosities similar to those of SFGs at larger distances from the nucleus. Thus, the extrapolation of the molecular gas mass from the PAH feature luminosity (e.g., as suggested by Co19) can induce a significant underestimation of M H 2 if the presence of nuclear activity has not been properly identified, as happens in the case of heavy extinction of weak nuclear emission; this is the case of some local, extremely obscured Seyfert 2 galaxies (e.g., Marchesi et al 2018).…”

Section: Pah As Tracer Of the Molecular Gassupporting

confidence: 92%

The molecular gas properties in local Seyfert 2 galaxies

Salvestrini

Gruppioni

Hatziminaoglou³

et al. 2022

A&A

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Aims. We present a multiwavelength study of the molecular gas properties of a sample of local Seyfert 2 galaxies to assess if, and to what extent, the presence of an active galactic nucleus (AGN) can affect the interstellar medium (ISM) properties in a sample of 33 local Seyfert 2 galaxies. Methods. We compare the molecular gas content (MH2) derived from new and archival low-J CO line measurements of a sample of AGN and a control sample of star-forming galaxies (SFGs). Both the AGN and the control sample are characterized in terms of host-galaxy properties, for example stellar and dust masses (M⋆ and Mdust, respectively) and the star formation rate (SFR). We also investigate the effect of AGN activity on the emission of polycyclic aromatic hydrocarbon (PAH) molecules in the mid-infrared (MIR), a waveband where the dust-reprocessed emission from the obscured AGN contributes the most. Result. The AGN hosted in less massive galaxies (i.e., M⋆ < 1010.5 M⊙; Mdust < 107.5 M⊙) show larger molecular gas contents with respect to SFGs that have the same stellar and dust masses. When comparing their depletion times (tdep ∝ MH2/SFR), AGN show tdep ∼ 0.3 − 1.0 Gyr, similar to the times observed in the control sample of SFGs. Seyfert 2 galaxies show fainter PAH luminosity the larger the dominance of the nuclear activity in the MIR. Conclusions. We find no clear evidence for a systematic reduction in the molecular gas reservoir at galactic scales in Seyfert galaxies with respect to SFGs. This is in agreement with recent studies that show that molecular gas content is only reduced in sub-kiloparsec-sized regions, where emission from the accreting supermassive black hole dominates. Nonetheless, we show that the impact of AGN activity on the ISM is clearly visible as a suppression of the PAH luminosity.

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Section: Pah As Tracer Of the Molecular Gassupporting

confidence: 92%

The molecular gas properties in local Seyfert 2 galaxies

Salvestrini

Gruppioni

Hatziminaoglou³

et al. 2022

A&A

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“…2. This is broadly in agreement with IRS results for AGN-dominated sources (Diamond-Stanic & Rieke 2010;García-Bernete et al 2022).…”

Section: Nuclear Versus Sf Pah Propertiessupporting

confidence: 92%

“…from García-Bernete et al 2022). The values of the 6.2/7.7 µm PAH ratios for the nuclear region of NGC 6552 are located in the region of large PAH molecules (N c ∼ 400; see the top panel of Fig.…”

Section: Nuclear Versus Sf Pah Propertiesmentioning

confidence: 94%

“…More recently, García-Bernete et al (2022) found that the PAH molecules responsible for the 11.3 µm PAH emission band are more resilient in the hard environments often present in AGN. In particular, the authors found larger 11.3/7.7 µm and 11.3/6.2 µm PAH ratios in AGN-dominated systems compared to SF galaxies, indicating a larger fraction of neutral PAH molecules (as noted by Smith et al 2007 using a sample of relatively weak AGN).…”

Section: Introductionmentioning

confidence: 99%

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A high angular resolution view of the PAH emission in Seyfert galaxies using JWST/MRS data

García-Bernete

Rigopoulou

Alonso‐Herrero

et al. 2022

A&A

Self Cite

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Polycyclic aromatic hydrocarbons (PAHs) are carbon-based molecules that are ubiquitous in a variety of astrophysical objects and environments. In this work we use JWST/MIRI MRS spectroscopy of three Seyferts to compare their nuclear PAH emission with that of star-forming (SF) regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts (Lbol > 1044.46 erg s−1) with a wide wavelength coverage (4.9–28.1 μm). We present an analysis of their nuclear PAH properties by comparing the observed ratios with PAH diagnostic model grids derived from theoretical spectra. Our results show that a suite of PAH features is present in the innermost parts of luminous Seyfert galaxies (∼0.45″ at 12 μm; in the inner ∼142–245 pc). We find that the nuclear regions of active galactic nuclei (AGN) lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. In particular, we find that the nuclear PAH emission mainly originates in neutral PAHs. In contrast, PAH emission originating in the SF regions favours ionised PAH grains. The observed PAH ratios in the nuclear region of the AGN-dominated galaxy NGC 6552 indicate the presence of larger PAH molecules compared with those of the SF regions. Therefore, our results provide evidence that the AGN have a significant impact on the ionisation state (and probably the size) of the PAH grains on scales of ∼142–245 pc.

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“…The mid-IR regime also provides strong evidence that an AGN affects its host galaxy's dust. As already brought up in Section 5.1, an AGN appears to affect both the size and ionization fraction of the PAH [69,163,164]. There may also be PAH carrier destruction as well but this appears to be localized to the nuclear regions around the AGN rather than the extended galaxies and affects shorter wavelength PAH features more than longer wavelength ones such as 11.3 µm (e.g., [50,66]).…”

Section: Dust Properties Around Agnmentioning

confidence: 86%

The Past and Future of Mid-Infrared Studies of AGN

2022

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Observational studies of AGN in the mid-infrared regime are crucial to our understanding of AGN and their role in the evolution of galaxies. Mid-IR-based selection of AGN is complementary to more traditional techniques allowing for a more complete census of AGN activity across cosmic time. Mid-IR observations including time variability and spatially resolved imaging have given us unique insights into the nature of the obscuring structures around AGN. The wealth of fine structure, molecular, and dust features in the mid-IR allow us to simultaneously probe multiple components of the ISM allowing us to explore in detail the impact on the host galaxy by the presence of an AGN—a crucial step toward understanding galaxy-SMBH co-evolution. This review gives a broad overview of this wide range of studies. It also aims to show the evolution of this field starting with its nascency in the 1960s, through major advances thanks to several generations of space-based and ground-based facilities, as well as the promise of upcoming facilities such as the James Webb Space Telescope (JWST).

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Polycyclic aromatic hydrocarbons in Seyfert and star-forming galaxies

Cited by 36 publications

References 115 publications

The molecular gas properties in local Seyfert 2 galaxies

The molecular gas properties in local Seyfert 2 galaxies

A high angular resolution view of the PAH emission in Seyfert galaxies using JWST/MRS data

The Past and Future of Mid-Infrared Studies of AGN

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