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

Mahitosh Ray, Chorng-Yuan Hwang

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.

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

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 away from the AGN. These two compact features appear as well-defined negative structures in the integrated intensity map from the velocity range of to . These two features are separated by a distance of 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.
Paper Structure (7 sections, 5 figures)

This paper contains 7 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Data reduction and analysis
  3. Results and Discussion
  4. Absorption features
  5. Interpretations for the origin of the compact features
  6. Interpretation for the line-shaped absorption features
  7. Conclusion

Figures (5)

  • Figure 1: Continuum emission image @114.04 GHz of nucleus and jet of M87.
  • Figure 2: Observed spectrum of the M87 central region around the SMBH.)
  • Figure 3: Left: Observed detection of the 2 absorption component in the central region of M87. The strong absorber is on the right and is in front of the AGN (ALMA-1), the weak absorber is the one on the left (ALMA-2). Right: Observed absorption components overlapped with the continuum emission (white contours) at 1, 3, 5, 7 and 9 $\sigma$.
  • Figure 4: Comparison of the ALMA integrated absorption map (top) with the HST data (middle) (reference: ads/Sa.HST#IC0601030), the green dashed circle shows the location of ALMA-1 and the sky blue dashed circle shows ALMA-2. Bottom image shows our ALMA data with the HST contours to show the location matching of the shock observed regions. White contours are drawn at 3, 6 and 9 $\sigma$ of HST image of the M87 nucleus and jet.
  • Figure 5: Observed spectra of the ALMA-1 and ALMA-2 regions. The blue curve shows the best-fit Gaussian model.