Ramírez-Moreta, P.; Verdes-Montenegro, L.; Blasco-Herrera, J.; Leon, S.; Venhola, A.; Yun, M.; Peris, V.; Peletier, R.; Verdoes Kleijn, G.; Unda-Sanzana, E.; Espada, D.; Bosma, A.; Athanassoula, E.; Argudo-Fernández, M.; Sabater, J.; Muñoz-Mateos, J. C.; Jones, M. G.; Huchtmeier, W.; Ruiz, J. E.; Iglesias-Páramo, J.; Fernández-Lorenzo, M.; Beckman, J.; Sánchez-Expósito, S.; Garrido, J.
Astronomy and Astrophysics, Volume 619, id.A163, 22 pp.
Context. Asymmetries in atomic hydrogen (HI) in galaxies are often
caused by the interaction with close companions, making isolated
galaxies an ideal framework to study secular evolution. The AMIGA
project has demonstrated that isolated galaxies show the lowest level of
asymmetry in their HI integrated profiles compared to even field
galaxies, yet some present significant asymmetries. CIG 96 (NGC 864) is
a representative case reaching a 16% level. Aims: Our aim is to
investigate the HI asymmetries of the spiral galaxy CIG 96 and what
processes have triggered the star-forming regions observed in the XUV
pseudo-ring. Methods: We performed deep optical observations at
CAHA1.23m, CAHA2.2m and VST (OmegaCAM wide-field camera) telescopes. We
reach surface brightness (SB) limits of μCAHA2.2m = 27.5
mag arcsec-2 (Cousins R) and μVST = 28.7 mag
arcsec-2 (SDSS r) that show the XUV pseudo-ring of the galaxy
in detail. Additionally, a wavelet filtering of the HI data cube from
our deep observations with VLA/EVLA telescope allowed us to reach a
column density of NHI = 8.9 × 1018
cm-2 (5σ) (28″ × 28″ beam), lower
than in any isolated galaxy. Results: We confirm that the HI of
CIG 96 extends farther than 4 × r25 in all directions.
Furthermore, we detect for the first time two gaseous structures
(˜106 M⊙) in the outskirts. The SDSS g -
r colour index image from CAHA1.23m shows extremely blue colours in
certain regions of the pseudo-ring where NHI > 8.5 ×
1020 cm-2, whereas the rest show red colours.
Galactic cirrus contaminate the field, setting an unavoidable detection
limit at 28.5 mag arcsec-2 (SDSS r). Conclusions: At
the current SB and NHI levels, we detect no stellar link
within 1° × 1° or gaseous link within 40' × 40'
between CIG 96 and any companion. The isolation criteria rule out
interactions with other similar-sized galaxies for at least ˜2.7
Gyr. Using existing stellar evolution models, the age of the pseudo-ring
is estimated at 1 Gyr or older. Undetected previously accreted
companions and cold gas accretion remain as the main hypothesis to
explain the optical pseudo-ring and HI features of CIG 96.
The reduced images and datacubes are only available at the CDS via
anonymous ftp to http://cdsarc.u-strasbg.fr
) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/163
Kinematic, Structural and Composition Studies of the Interstellar and Intergalactic Media
The basic objective of the broject is to investigate the evolution of galaxies by deepening our understanding of the interaction between the insterstellar medium and the stars.The main technique which we use is the two-dimensional kinematic study of whole galaxies observed using our instrument:GHaFaS, a Fabry-Perot interferometer on the William