J/A+A/587/A68 Ionised gas images of NGC 4569 (Boselli+, 2016)
Spectacular tails of ionised gas in the Virgo cluster galaxy NGC 4569.
Boselli A., Cuillandre J.C., Fossati M., Boissier S., Bomans D.,
Consolandi G., Anselmi G., Cortese L., Cote P., Durrell P., Ferrarese L.,
Fumagalli M., Gavazzi G., Gwyn S., Hensler G., Sun M., Toloba E.
<Astron. Astrophys. 587, A68 (2016)>
=2016A&A...587A..68B 2016A&A...587A..68B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, nearby
Keywords: galaxies: individual: NGC 4569 - galaxies: clusters: general -
galaxies: clusters: individual: Virgo - galaxies: evolution -
galaxies: interactions - galaxies: ISM
Abstract:
Using MegaCam at the CFHT, we obtained a deep narrow band
Hα+[NII] wide-field image of NGC 4569 (M90), the brightest
late-type galaxy in the Virgo cluster. The image reveals the presence
of long tails of diffuse ionized gas, without any associated stellar
component extending from the disc of the galaxy up to ~=80kpc
(projected distance) and with a typical surface brightness of a few
10-18erg/s/cm2/arcsec2. These features provide direct evidence
that NGC 4569 is undergoing a ram-pressure stripping event. The image
also shows a prominent 8 kpc spur of ionized gas that is associated
with the nucleus that spectroscopic data identify as an outflow. With
some assumptions on the 3D distribution of the gas, we use the
Hα surface brightness of these extended low-surface brightness
features to derive the density and the mass of the gas that has been
stripped during the interaction of the galaxy with the intracluster
medium. The comparison with ad hoc chemo-spectrophotometric models of
galaxy evolution indicates that the mass of the Hα emitting gas
in the tail is a large fraction of that of the cold phase that has
been stripped from the disc, suggesting that the gas is ionized within
the tail during the stripping process. The lack of star-forming
regions suggests that mechanisms other than photoionization are
responsible for the excitation of the gas (shocks, heat conduction,
magneto hydrodynamic waves). This analysis indicates that ram pressure
stripping is efficient in massive (M*~=1010.5M☉)
galaxies located in intermediate-mass (~=1014M_☉) clusters under
formation. It also shows that the mass of gas expelled by the nuclear
outflow is only ∼1% than that removed during the ram pressure
stripping event. Together these results indicate that ram pressure
stripping, rather than starvation through nuclear feedback, can be the
dominant mechanism that is responsible for the quenching of the star
formation activity of galaxies in high density environments.
Description:
Narrow-band imaging observations were carried out in May 2015 using
MegaCam at the CFHT. The galaxy NGC 4569, which has a recessional
velocity of -221km/s, was observed in the narrow-band filter MP9603
that was centered on the Hα line (λ= 6590Å;
Δλ= 104Å, T=93%).
Long-slit spectroscopy observations were carried out in 2001 with the
Calar Alto 3.5m telescope using the Twin spectrograph. Its was
observed with the T05 and T06 gratings in the blue (4430Å) and red
(6562Å) arm of the spectrograph with a dispersion of 36Å/mm and
a spatial sampling of 0.56-arcsec/pixel.
Objects:
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RA (2000) DE Designation(s)
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12 36 49.82 +13 09 46.3 NGC 4569 = M 90
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 106 3 List of fits images
fits/* . 3 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 24 F5.3 arcsec/pix scale ? Scale of the image
26- 29 I4 --- Nx Number of pixels along X-axis
31- 34 I4 --- Ny Number of pixels along Y-axis
36- 41 I6 Kibyte size Size of FITS file
43- 72 A30 --- FileName Name of FITS file, in subdirectory fits
74-106 A33 --- Title Title of the FITS file (1)
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Note (1): the zero point for the transformation of counts into fluxes in the
Halpha image is -15.39 (in log; erg/s/cm2/arcsec2).
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Acknowledgements:
Alessandro Boselli, Alessandro.Boselli(at)lam.fr
(End) Patricia Vannier [CDS] 26-Jan-2016