Spectroscopic Detection of a Cusp of Late-type Stars around the Central Black Hole in the Milky Way

Habibi, M.; Gillessen, S.; Pfuhl, O.; Eisenhauer, F.; Plewa, P. M.; Fellenberg, S. von; Widmann, F.; Ott, Thomas; Gao, F.; Waisberg, I.; Bauböck, M.; Jiménez-Rosales, A.; Dexter, Jason; Zeeuw, P. T. de; Genzel, R.

doi:10.3847/2041-8213/ab03cf

Cited by 34 publications

(65 citation statements)

References 53 publications

(107 reference statements)

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“…It appears therefore reasonable to assume that stars A102, page 12 of 19 older than a few Gyr are dynamically relaxed at the GC. The expected stellar cusp is not observed for bright giants, but has been confirmed to be present for stars fainter than K s ≈ 15.5 (Yusef-Zadeh et al 2012;Gallego-Cano et al 2018;Schödel et al 2018;Habibi et al 2019). Here we present even deeper star counts than in Gallego-Cano et al (2018) and confirm that the cusp is consistently detected in the form of a powerlaw increase of the stellar surface density towards Sgr A*.…”

Section: Stellar Cusp Around Sgr A*mentioning

confidence: 91%

“…The stellar cusp at the GC has been at the focus of intense and partially controversial studies over the past decade (Genzel et al 2003;Schödel et al 2007;Buchholz et al 2009;Do et al 2009; Bartko et al 2010) because the presence of young, massive stars, high interstellar extinction that varies on arcsecond scales, extreme source crowding, and the unknown contamination by young or intermediate age, non-relaxed stars are issues that are difficult to tackle. Recent photometric and spectroscopic work, combined with simulations, appears to provide, finally, robust evidence for the existence of the predicted stellar cusp (Gallego-Cano et al 2018;Schödel et al 2018;Baumgardt et al 2018;Habibi et al 2019). Recently, evidence for a cusp of stellar mass black holes at the GC was found from X-ray observations (Hailey et al 2018).…”

Section: Introductionmentioning

confidence: 92%

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The Milky Way’s nuclear star cluster: Old, metal-rich, and cuspy

Schödel

Nogueras-Lara

Gallego-Cano

et al. 2020

A&A

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Context. The environment of Sagittarius A* (Sgr A*), the central black hole of the Milky Way, is the only place in the Universe where we can currently study the interaction between a nuclear star cluster and a massive black hole and infer the properties of a nuclear cluster from observations of individual stars. Aims. This work aims to explore the star formation history of the nuclear cluster and the structure of the innermost stellar cusp around Sgr A*. Methods. We combined and analysed multi epoch high quality AO observations. For the region close to Sgr A* we apply the speckle holography technique to the AO data and obtain images that are ≥50% complete down to Ks ≈ 19 within a projected radius of 5″ around Sgr A*. We used H-band images to derive extinction maps. Results. We provide Ks photometry for roughly 39 000 stars and H-band photometry for ∼11 000 stars within a field of about 40″ × 40″, centred on Sgr A*. In addition, we provide Ks photometry of ∼3000 stars in a very deep central field of 10″ × 10″, centred on Sgr A*. We find that the Ks luminosity function (KLF) is rather homogeneous within the studied field and does not show any significant changes as a function of distance from the central black hole on scales of a few 0.1 pc. By fitting theoretical luminosity functions to the KLF, we derive the star formation history of the nuclear star cluster. We find that about 80% of the original star formation took place 10 Gyr ago or longer, followed by a largely quiescent phase that lasted for more than 5 Gyr. We clearly detect the presence of intermediate-age stars of about 3 Gyr in age. This event makes up about 15% of the originally formed stellar mass of the cluster. A few percent of the stellar mass formed in the past few 100 Myr. Our results appear to be inconsistent with a quasi-continuous star formation history. The mean metallicity of the stars is consistent with being slightly super solar. The stellar density increases exponentially towards Sgr A* at all magnitudes between Ks = 15−19. We also show that the precise properties of the stellar cusp around Sgr A* are hard to determine because the star formation history suggests that the star counts can be significantly contaminated, at all magnitudes, by stars that are too young to be dynamically relaxed. We find that the probability of observing any young (non-millisecond) pulsar in a tight orbit around Sgr A* and beamed towards Earth is very low. We argue that typical globular clusters, such as they are observed in and around the Milky Way today, have probably not contributed to the nuclear cluster’s mass in any significant way. The nuclear cluster may have formed following major merger events in the early history of the Milky Way.

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Section: Stellar Cusp Around Sgr A*mentioning

confidence: 91%

Section: Introductionmentioning

confidence: 92%

The Milky Way’s nuclear star cluster: Old, metal-rich, and cuspy

Schödel

Nogueras-Lara

Gallego-Cano

et al. 2020

A&A

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“…Both population of young (B-type) or old (G, K, and M type) giant stars (post main-sequence) are observed in this region (e.g., Ghez et al 2003). The stars in Habibi et al (2017) belong to the early-type group and in Habibi et al (2019) belong to the late-type group. Habibi et al (2017) derived specifically the masses of 8 stars in early-type group.…”

Section: Methodsmentioning

confidence: 99%

“…We use their evaluation to estimate the mass of other early-type stars which have a similar magnitude (m k ) to the stars which are studied in Habibi et al (2017) and for the rest of early-type S-stars (fainter ones) we assume the mass range of 8−14M ⊙ . Furthermore, Habibi et al (2019) measured an initial-mass range of 0.5−2M ⊙ for the older stars (∼ few Gyr old). We also implement the mass range of 0.5 − 2M ⊙ for late-type stars in our simulations.…”

Section: Methodsmentioning

confidence: 99%

Interaction of stars hosting planets with Sgr A* black hole

2019

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We present some preliminary results of our ongoing project about planetary systems around S-stars in the vicinity of Sgr A* black hole. Since S-stars might have migrated in the Galactic Centre (GC) from elsewhere, they probably still keep their planetary systems throughout their voyage. In this work, we study the destiny of their putative planetary systems after close interaction with the central black hole of our galaxy.

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“…Stellar formation in the Galactic Center was investigated by, e.g., Morris (1993), Kauffmann (2016), and Kruijssen et al (2019). It should be recalled that 8 out of the roughly 40 stars constituting the S-star cluster orbiting Sgr A * in the central arcsecond of the Galactic Center (GC) are old, main sequence stars of spectral classes G, K, and M whose masses are in the range 0.5 − 2 M ⊙ (Habibi et al 2019;Davari, Capuzzo-Dolcetta & Spurzem 2019). The evolution of a fictitious planetary system like our solar system around a S-type star orbiting the SMBH in Sgr A * was recently studied by Davari, Capuzzo-Dolcetta & Spurzem (2019), who recalled that the existence of planetary systems in the innermost pc of Sgr A * is still debated (Trani et al 2016), being, perhaps, due to migration instead of in situ formation.…”

Section: Introductionmentioning

confidence: 99%

What Would Happen if We Were About 1 pc Away from a Supermassive Black Hole?

Iorio

2020

ApJ

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We consider a hypothetic planet with the same mass m, radius R, angular momentum S, oblateness J 2 , semimajor axis a, eccentricity e, inclination I, and obliquity ε of the Earth orbiting a main sequence star with the same mass M ⋆ and radius R ⋆ of the Sun at a distance r • ≃ 1 parsec pc from a supermassive black hole in the center of the hosting galaxy with the same mass M • of, say, M87 * . We preliminarily investigate some dynamical consequences of its presence in the neighbourhood of such a stellar system on the planet's possibility of sustaining complex life over the eons. In particular, we obtain general analytic expressions for the long-term rates of change, doubly averaged over both the planetary and the galactocentric orbital periods P b and P • , of e, I, ε, which are the main quantities directly linked to the stellar insolation. We find that, for certain orbital configurations, the planet's perihelion distance q = a (1 − e) may greatly shrink leading, in some cases, even to an impact with the star. Also I may notably change, with variations of the order even of tens of degrees. On the other hand, ε does not seem to be particularly affected, being shifted, at most, by ≃ 0.02 deg over a Myr. Our results strongly depend the eccentricity e • of the galactocentric motion. keywords gravitation − celestial mechanics − (galaxies:) quasars: supermassive black holes − planetary systems − extraterrestrial intelligence

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Spectroscopic Detection of a Cusp of Late-type Stars around the Central Black Hole in the Milky Way

Cited by 34 publications

References 53 publications

The Milky Way’s nuclear star cluster: Old, metal-rich, and cuspy

The Milky Way’s nuclear star cluster: Old, metal-rich, and cuspy

Interaction of stars hosting planets with Sgr A* black hole

What Would Happen if We Were About 1 pc Away from a Supermassive Black Hole?

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