Kavli Affiliate: Pau Amaro Seoane
| First 5 Authors: The GRAVITY Collaboration, Karim Abd El Dayem, Roberto Abuter, Nicolas Aimar, Pau Amaro Seoane
| Summary:
Studying the orbital motion of stars around Sagittarius A* in the Galactic
Center provides a unique opportunity to probe the gravitational potential near
the supermassive black hole at the heart of our Galaxy. Interferometric data
obtained with the GRAVITY instrument at the Very Large Telescope Interferometer
(VLTI) since 2016 has allowed us to achieve unprecedented precision in tracking
the orbits of these stars. GRAVITY data have been key to detecting the
in-plane, prograde Schwarzschild precession of the orbit of the star S2, as
predicted by General Relativity. By combining astrometric and spectroscopic
data from multiple stars, including S2, S29, S38, and S55 – for which we have
data around their time of pericenter passage with GRAVITY – we can now
strengthen the significance of this detection to an approximately $10 sigma$
confidence level. The prograde precession of S2’s orbit provides valuable
insights into the potential presence of an extended mass distribution
surrounding Sagittarius A*, which could consist of a dynamically relaxed
stellar cusp comprised of old stars and stellar remnants, along with a possible
dark matter spike. Our analysis, based on two plausible density profiles – a
power-law and a Plummer profile – constrains the enclosed mass within the orbit
of S2 to be consistent with zero, establishing an upper limit of approximately
$1200 , M_odot$ with a $1 sigma$ confidence level. This significantly
improves our constraints on the mass distribution in the Galactic Center. Our
upper limit is very close to the expected value from numerical simulations for
a stellar cusp in the Galactic Center, leaving little room for a significant
enhancement of dark matter density near Sagittarius A*.
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