J/A+A/633/A79 NGC 6240 MUSE observations (Kollatschny+, 2020)
NGC 6240: A triple nucleus system in the advanced or final state of merging.
Kollatschny W., Weilbacher P.M., Ochmann M.W., Chelouche D.,
Monreal-Ibero A., Bacon R., Contini T.
<Astron. Astrophys. 633, A79 (2020)>
=2020A&A...633A..79K 2020A&A...633A..79K (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Spectroscopy ; Spectrophotometry
Keywords: galaxies: active - galaxies: interactions -
instrumentation: high angular resolution -
galaxies: individual: NGC 6240 - galaxies: nuclei
Abstract:
NGC 6240 is a well-studied nearby galaxy system in the process of
merging. Based on optical, X-ray, and radio observations, it is
thought to harbor two active nuclei. We carried out a detailed optical
3D spectroscopic study to investigate the inner region of this system
in connection with existing MERLIN and VLBA data.
We observed NGC 6240 with very high spatial resolution using the MUSE
instrument in the Narrow-Field Mode with the four-laser GALACSI
adaptive optics system on the ESO VLT under seeing conditions of
0.49''. Our 3D spectra cover the wavelength range from 4725 to 9350
Angstroem at a spatial resolution of about 75 mas.
We report the discovery of three nuclei in the final state of merging
within a region of only 1 kpc in the NGC 6240 system. Thanks to MUSE
we are able to show that the formerly unresolved southern component
actually consists of two distinct nuclei separated by only 198pc. In
combination with Gaia data we reach an absolute positional accuracy of
only 30mas that is essential to compare optical spectra with MERLIN
and VLBA radio positions.
The verification and detailed study of a system with three nuclei, two
of which are active and each with a mass in excess of 9x107M☉,
is of great importance for the understanding of hierarchical galaxy
formation via merging processes since multiple mergers lead to a
faster evolution of massive galaxies in comparison to binary mergers.
So far it has been suggested that the formation of galactic nuclei
with multiple supermassive black holes (SMBHs) is expected to be rare
in the local universe. Triple massive black hole systems might be of
fundamental importance for the coalescence of massive black hole
binaries in less than a Hubble time leading to the loudest sources of
gravitational waves in the megahertz regime.
Description:
We provide the MUSE datacube, observed in Narrow Field Mode NFM, and
combined from four 500s exposures. The data is flux-calibrated (see
FITS keyword BUNIT), the wavelength planes affected by the NaD laser
system and notch filter were masked and appear as NANs.
The data itself is contained in FITS extension 'DATA', the associated
variance in 'STAT'. Further FITS extensions are 2D images, integrated
over different wavelength ranges ('white': full wavelength range,
'Johnson_V', 'Cousins_R', and 'Cousins_I': using the respective filter
curve). All relevant information is contained in the FITS headers,
including the original world coordinates (primary WCS) and world
coordinates corrected with reference to Gaia DR2 (WCS G).
Objects:
-----------------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------------
16 52 58.86 +02 24 03.5 NGC 6240 = IC 4625
-----------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 123 1 Information of fits file
fits/* . 1 Individual fits file
--------------------------------------------------------------------------------
See also:
J/A+A/549/A51 : Extended CO structures in NGC6240 (Feruglio+, 2013)
J/A+A/558/A87 : NGC6240 high resolution mapping of CO(1-0) (Feruglio+, 2013)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 25 F6.4 arcsec/pix Scale Scale of the image
27- 29 I3 --- Nx Number of pixels along X-axis
31- 33 I3 --- Ny Number of pixels along Y-axis
35- 57 A23 "datime" Obs.date Observation date
59- 65 I7 Kibyte size Size of FITS file
67- 78 A12 --- FileName Name of FITS file, in subdirectory fits
80-123 A44 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Peter Weilbacher, pweilbacher(at)aip.de
(End) Patricia Vannier [CDS] 13-Nov-2019