The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. I. Detection of a Rich Population of Dusty Objects in the IRS 13 Cluster

Abstract

A detailed analysis of the nuclear star cluster not only concedes the existence of the S cluster, with its fast-moving stars and the supermassive black hole Sgr A*. It also reveals an embedded region of gas and dust with an exceptionally high stellar density called IRS 13. The IRS 13 cluster can be divided into the northern and eastern counterparts, called IRS 13N and IRS 13E, respectively. This work will focus on both regions and study their most prominent members using rich infrared and radio/submillimeter data baselines. Applying a multiwavelength analysis enables us to determine a comprehensive photometric footprint of the investigated cluster sample. Using the ray-tracing-based radiative transfer model HYPERION, the spectral energy distribution of the IRS 13 members suggests a stellar nature of the dusty sources. These putative young stellar objects (YSOs) have a comparable spectroscopic identification to the D and G sources in or near the S cluster. Furthermore, we report the existence of a population of dusty sources in IRS 13 that can be mostly identified in the H, K, and L band. We propose that, together with the objects reported in the literature, this population is the outcome of a recent star formation process. Furthermore, we report that these presumably young objects are arranged in a disk structure. Although it cannot be excluded that the intrinsic arrangement of IRS 13 does show a disk structure, we find indications that the investigated cluster sample might be related to the counterclockwise disk.

The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic Structure

“…We adopt the X-ray luminosity constraint in the 2-10 keV band from Zhu et al (2020), while the infrared flux densities in the H, K, L, and M bands are taken from Paper I (Peißker et al 2023c) for which we used the peak intensity of IRS 13E3. The low-frequency mm/radio flux densities at 340, 232, and Figure 11.…”

“…For comparison, we also show the SED of Sgr A * (dashed gray line), whose peak is shifted to longer wavelengths in the mm domain. The X-ray measurement in the 2-10 keV band was adopted from Zhu et al (2020), infrared measurements were taken from Peißker et al (2023c), and the mm and radio data are adopted according to Tsuboi et al (2019) and Tsuboi et al (2017a). Observed regions are highlighted in orange, red, and blue for radio/mm, infrared, and X-ray bands respectively.…”

“…Due to technological evolution and the introduction of active optics that allowed larger telescope dishes (Wilson et al 1987), high spatial resolution observations with the SHARP camera showed a dense collection of stars that already implied a cluster arrangement (Krabbe et al 1995;Menten et al 1997). Taking into account a rather poor coverage of the interesting cluster IRS 13, we concentrated on the analysis of single stellar objects in Peißker et al (2023c), hereafter Paper I. In this paper, we identified over 30 new stellar objects that we classified to a large extent as the YSO candidates that coexist with mainsequence stars, such as E1-E4 (Maillard et al 2004;Mužić et al 2008).…”

“…Furthermore, we present Dopplershifted Atacama Large Millimeter/submillimeter Array (ALMA) data that show an ionized arrangement of H30α enveloping the projected position of IRS 13E3 (Murchikova et al 2019;Tsuboi et al 2019). For the region corresponding to this source, we collect radio/mm, infrared, and X-ray data from the literature (Tsuboi et al 2017a(Tsuboi et al , 2019Zhu et al 2020;Peißker et al 2023c) and find that the broadband spectral properties can be described by the hot accretion flow model, which provides tentative support for the hypothetical presence of the intermediate-mass black hole (IMBH).…”