The Mice at play in the CALIFA survey. A case study of a gas-rich major merger between first passage and coalescence

Autor(en)

Vivienne Wild, Fabian Rosales-Ortega, Jesus Falcón-Barroso, Rubén García-Benito, Anna Gallazzi, Rosa M. González Delgado, Simona Bekeraité, Anna Pasquali, Peter H. Johansson, Begoña García Lorenzo, Glenn van de Ven, Milena Pawlik, Enrique Peréz, Ana Monreal-Ibero, Mariya Lyubenova, Roberto Cid Fernandes, Jairo Méndez-Abreu, Jorge Barrera-Ballesteros, Carolina Kehrig, Jorge Iglesias-Páramo, Dominik J. Bomans, Isabel Márquez, Benjamin D. Johnson, Robert C. Kennicutt, Bernd Husemann, Damian Mast, Sebastian F. Sánchez, C. Jakob Walcher, João Alves, Alfonso L. Aguerri, Almudena Alonso Herrero, Joss Bland-Hawthorn, Cristina Catalán-Torrecilla, Estrella Florido, Jean Michel Gomes, Knud Jahnke, Á. R. López-Sánchez, Adriana de Lorenzo-Cáceres, Raffaella A. Marino, Esther Mármol-Queraltó, Patrick Olden, Ascensión del Olmo, Polychronis Papaderos, Andreas Quirrenbach, Jose M. Vílchez, Bodo Ziegler

Abstrakt

We present optical integral field spectroscopy (IFS) observations of the

Mice, a major merger between two massive (≳1011

M⊙) gas-rich spirals NGC 4676A and B, observed between

first passage and final coalescence. The spectra provide stellar and gas

kinematics, ionised gas properties, and stellar population diagnostics,

over the full optical extent of both galaxies with ~1.6 kpc spatial

resolution. The Mice galaxies provide a perfect case study that

highlights the importance of IFS data for improving our understanding of

local galaxies. The impact of first passage on the kinematics of the

stars and gas has been significant, with strong bars most likely induced

in both galaxies. The barred spiral NGC 4676B exhibits a strong twist in

both its stellar and ionised gas disk. The edge-on disk galaxy NGC 4676A

appears to be bulge free, with a strong bar causing its "boxy" light

profile. On the other hand, the impact of the merger on the stellar

populations has been minimal thus far. By combining the IFS data with

archival multiwavelength observations we show that star formation

induced by the recent close passage has not contributed significantly to

the total star formation rate or stellar mass of the galaxies. Both

galaxies show bicones of high ionisation gas extending along their minor

axes. In NGC 4676A the high gas velocity dispersion and Seyfert-like

line ratios at large scaleheight indicate a powerful outflow. Fast

shocks (vs ~ 350 km s-1) extend to ~6.6 kpc above

the disk plane. The measured ram pressure (P/k = 4.8 ×

106 K cm-3) and mass outflow rate (~8-20

M⊙ yr-1) are similar to superwinds from local

ultra-luminous infrared galaxies, although NGC 4676A only has a moderate

infrared luminosity of 3 × 1010 L⊙.

Energy beyond what is provided by the mechanical energy of the starburst

appears to be required to drive the outflow. Finally, we compare the

observations to mock kinematic and stellar population maps extracted

from a hydrodynamical merger simulation. The models show little

enhancement in star formation during and following first passage, in

agreement with the observations. We highlight areas where IFS data could

help further constrain the models.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

Universidad de Granada, Centro Astronómico Hispano Alemán (CAHA), Universidad Autónoma de Madrid, Universidad de La Laguna, Macquarie University, Universidad Complutense De Madrid, University of St. Andrews, The Royal Observatory, Edinburgh, National Institute of Astrophysics, Optics and Electronics (INAOE), Instituto de Astrofísica de Canarias (IAC), Instituto de Astrofísica de Andalucía, INAF - Osservatorio Astrofisico di Arcetri, University of Copenhagen, Leibniz-Institut für Astrophysik Potsdam, Universität Heidelberg, University of Helsinki, Max-Planck-Institut für Astronomie, Université Paris VII - Paris-Diderot, Universidade Federal de Santa Catarina, Ruhr-Universität Bochum (RUB), Université Paris VI - Pierre-et-Marie-Curie, University of Cambridge, European Southern Observatory (Germany), Centro Brasileiro de Pesquisas Físicas (CBPF), Universidad Nacional Autonoma de Mexico, Universidad de Cantabria, The University of Sydney, Universidade do Porto, Australian Astronomical Observatory, Landessternwarte Königstuhl (LSW)

Journal