Top-heavy stellar mass distribution in galactic nuclei inferred from the universally high abundance ratio of [Fe/Mg]

Toyouchi, Daisuke; Inayoshi, Kohei; Ishigaki, Miho N.; Tominaga, Nozomu

doi:10.48550/arxiv.2112.06151

Cited by 5 publications

(4 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Artymowicz et al 1993;Shields 1996), star formation inside quasar accretion disks (e.g. Collin & Zahn 1999;Goodman & Tan 2004;Toyouchi et al 2021), or nucleosynthesis without stars (e.g. Chakrabarti & Mukhopadhyay 1999;Hu & Peng 2008;Datta & Mukhopadhyay 2019) are also capable of producing highly enriched BLRs in a short time.…”

Section: Discussionmentioning

confidence: 99%

Chemical abundance of z ~ 6 quasar broad-line regions in the XQR-30 sample

Lai

Bian

Onken

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The elemental abundances in the broad-line regions of high-redshift quasars trace the chemical evolution in the nuclear regions of massive galaxies in the early universe. In this work, we study metallicity-sensitive broad emission-line flux ratios in rest-frame UV spectra of 25 high-redshift (5.8 < z < 7.5) quasars observed with the VLT/X-shooter and Gemini/GNIRS instruments, ranging over $\log \left({\rm {M}_{\rm {BH}}/\rm {M}_{\odot }}\right) = 8.4-9.8$ in black hole mass and $\log \left(\rm {L}_{\rm {bol}}/\rm {erg \, s}^{-1}\right) = 46.7-47.7$ in bolometric luminosity. We fit individual spectra and composites generated by binning across quasar properties: bolometric luminosity, black hole mass, and blueshift of the C iv line, finding no redshift evolution in the emission-line ratios by comparing our high-redshift quasars to lower-redshift (2.0 < z < 5.0) results presented in the literature. Using Cloudy-based locally optimally-emitting cloud photoionisation model relations between metallicity and emission-line flux ratios, we find the observable properties of the broad emission lines to be consistent with emission from gas clouds with metallicity that are at least 2-4 times solar. Our high-redshift measurements also confirm that the blueshift of the C iv emission line is correlated with its equivalent width, which influences line ratios normalised against C iv. When accounting for the C iv blueshift, we find that the rest-frame UV emission-line flux ratios do not correlate appreciably with the black hole mass or bolometric luminosity.

show abstract

Section: Discussionmentioning

confidence: 99%

Chemical abundance of z ~ 6 quasar broad-line regions in the XQR-30 sample

Lai

Bian

Onken

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Stellar models suggest relatively modest metal yields in the immortal phase, of order 10 −4 times that of helium (Dittmann et al 2021), indicating that immortals are unlikely to contribute much to the metal fraction. Interestingly, we expect significantly higher (∼ 0.03M yr −1 per star, Toyouchi et al 2021) metal yields for mortal stars embedded in the disk because these still become massive but are still able to evolve towards later stages of nuclear burning in addition to further metal enrichment from supernovae (see also Artymowicz et al 1993). It could then be that mortal stars further out in the disk contribute the most to metal-enrichment, while helium production is the domain of the immortals.…”

Section: Chemical Evolutionmentioning

confidence: 92%

Effects of an Immortal Stellar Population in AGN Disks

Jermyn,

Dittmann,

McKernan

et al. 2022

Preprint

View full text Add to dashboard Cite

Stars are likely embedded in the gas disks of Active Galactic Nuclei (AGN). Theoretical models predict that in the inner regions of the disk these stars accrete rapidly, with fresh gas replenishing hydrogen in their cores faster than it is burned into helium, effectively stalling their evolution at hydrogen burning. We produce order-of-magnitude estimates of the number of such stars in a fiducial AGN disk. We find numbers of order 10 2−4 , confined to the inner r cap ∼ 3000r s ∼ 0.03pc. These stars can profoundly alter the chemistry of AGN disks, enriching them in helium and depleting them in hydrogen, both by order-unity amounts. We further consider mergers between these stars and other disk objects, suggesting that star-star mergers result in rapid mass loss from the remnant to restore an equilibrium mass, while star-compact object mergers may result in exotic outcomes and even host binary black hole mergers within themselves. Finally, we examine how these stars react as the disk dissipates towards the end of its life, and find that they may return mass to the disk fast enough to extend its lifetime by a factor of several and/or may drive powerful outflows from the disk. Post-AGN, these stars rapidly lose mass and form a population of stellar mass black holes around 10M . Due to the complex and uncertain interactions between embedded stars and the disk, their plausible ubiquity, and their order unity impact on disk structure and evolution, they must be included in realistic disk models.

show abstract

“…Furthermore, recent studies (e.g. Zhang et al 2018;Toyouchi et al 2021) found that the stellar initial mass function (IMF) characterizing starbursting systems is generally top-heavy (note that the Mikly Way nucleus, which is by far the best known galactic nucleus, is also characterized by a top-heavy IMF, see e.g. Bartko et al 2010;Lu et al 2013), meaning that more massive stars are formed more efficiently in comparison with the commonly adopted IMFs (e.g.…”

Section: Introductionmentioning

confidence: 99%

Tidal disruption events in post-starburst galaxies: the importance of a complete stellar mass function

Bortolas

2022

Preprint

View full text Add to dashboard Cite

A tidal disruption event (TDE) occurs when a star is destroyed by the strong tidal shear of a massive black hole (MBH). The accumulation of TDE observations over the last years has revealed that poststarburst galaxies are significantly overrepresented in the sample of TDE hosts. Here we address the poststarburst preference by investigating the decline of TDE rates in a Milky-Way like nuclear stellar cluster featuring either a monochromatic (1 M ) or a complete, evolved stellar mass function. In the former case, the decline of TDE rates with time is very mild, and generally up to a factor of a few in 10 Gyr. Conversely, if a complete mass function is considered, a strong TDE burst over the first 0.1 − 1 Gyr is followed by a considerable rate drop, by at least an order of magnitude over 10 Gyr. The decline starts after a mass segregation timescale, and it is more pronounced assuming a more top-heavy initial mass function and/or an initially denser nucleus. Our results thus suggest that the poststarburst preference can be accounted for in realistic systems featuring a complete stellar mass function, even in moderately dense galactic nuclei. Overall, our findings support the idea that starbursting galactic nuclei are characterized by a top-heavy initial mass function; we speculate that accounting for this can reconcile the discrepancy between observed and theoretically predicted TDE rates even in quiescent galaxies.

show abstract

Top-heavy stellar mass distribution in galactic nuclei inferred from the universally high abundance ratio of [Fe/Mg]

Cited by 5 publications

References 69 publications

Chemical abundance of z ~ 6 quasar broad-line regions in the XQR-30 sample

Chemical abundance of z ~ 6 quasar broad-line regions in the XQR-30 sample

Effects of an Immortal Stellar Population in AGN Disks

Tidal disruption events in post-starburst galaxies: the importance of a complete stellar mass function

Contact Info

Product

Resources

About