Compact Absorbers surrounding the M87 AGN Revealed by ALMA Band 3 Observations1

TL;DR

This study uses ALMA Band 3 observations to detect and analyze compact and extended molecular absorption features around the M87 nucleus, revealing structures possibly related to the SMBH environment and jet interactions.

Contribution

First detection of compact molecular absorption features near M87's SMBH, providing insights into the nuclear environment and jet-related shock regions.

Findings

Two compact absorption features near M87's nucleus separated by ~40 pc.

Extended absorption features aligned perpendicular to the jet, indicating shock regions.

Features suggest dense molecular fragments possibly related to SMBH feeding or torus structures.

Abstract

We report detection of two compact absorption features surrounding the M87 nucleus and some extended absorption features perpendicular to the M87 jet using the Atacama Large millimeter-submillimeter-Array (ALMA) Band 3 data. One compact absorption feature appears at the position of the M87 AGN and the other $0.5\arcsec$ away from the AGN. These two compact features appear as well-defined negative structures in the integrated intensity map from the velocity range of $-500$ to $+2000~{\rm km~s^{-1}}$. These two features are separated by a distance of $\sim$40~pc assuming the distance of M87. The origin of these features could be dense molecular fragments associated with super massive black holes (SMBHs), possibly associated with a rotating torus filament, or in-falling molecular fragments/objects feeding the nucleus. The extended absorption features perpendicular to the jet appear in all velocity ranges and can be caused by shock compressed regions associated with the jet knots A and C.