Abstract

ABSTRACT The population of intermediate-mass black holes (IMBHs) in nearby dwarf galaxies plays an important ‘ground truth’ role in exploring black hole formation and growth in the early Universe. In the dwarf elliptical galaxy SDSS J090613.77+561015.2 (z = 0.0465), an accreting IMBH has been revealed by optical and X-ray observations. Aiming to search for possible radio core and jet associated with the IMBH, we carried out very long baseline interferometry (VLBI) observations with the European VLBI Network at 1.66 GHz. Our imaging results show that there are two 1-mJy components with a separation of about 52 mas (projected distance 47 pc) and the more compact component is located within the 1σ error circle of the optical centroid from available Gaia astrometry. Based on their positions, elongated structures and relatively high brightness temperatures, as well as the absence of star-forming activity in the host galaxy, we argue that the radio morphology originates from the jet activity powered by the central IMBH. The existence of the large-scale jet implies that violent jet activity might occur in the early epochs of black hole growth and thus help to regulate the co-evolution of black holes and galaxies.

Highlights

  • The population of low-mass black holes (BHs) in nearby dwarf galaxies, i.e. galaxies with Mg ≤ 109.5 M, plays a key role in shedding light on BH formation and growth in the early Universe

  • These BHs with masses of 102 M ≤ Mbh ≤ 106 M are typically classified as intermediate-mass black holes (IMBHs)

  • The optical spectroscopic observations of SDSS J090613.77+561015.2 show that there are no signatures for on-going star-forming activity in the BPT (Baldwin, Phillips & Terlevich 1981) diagrams formed with some emission-line ratios (Reines et al 2020)

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Summary

INTRODUCTION

The population of low-mass black holes (BHs) in nearby dwarf galaxies, i.e. galaxies with Mg ≤ 109.5 M , plays a key role in shedding light on BH formation and growth in the early Universe. High-resolution very long baseline interferometry (VLBI) observations of these radio counterparts provide direct insight in their nature and mechanism of emission, involving non-thermal radio jet/outflow activity. Both jets and wide opening angle winds. In the long-slit spectroscopy with the Keck I telescope, it shows some spatially extended ionized gas outflows that are most likely AGN-driven because their velocity (701 ± 7 km s−1) exceeds the escape velocity (303 ± 35 km s−1) of its halo (Manzano-King et al 2019) It is a slightly resolved point-like source with total the flux density of 22.4 ± 4.1 mJy in the GMRT (Giant Metrewave Radio Telescope) 150 MHz all-sky radio survey (Intema et al 2017) and 4.7 ± 0.2 mJy in the 1.4 GHz FIRST survey (Becker et al 1995).

VLBIOBSE RVAT IONSAND DATA REDUCTION
The nature of the components N and S
Findings
Implications of the presence of a radio jet associated with the IMBH

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