The Effects of Ram-pressure Stripping and Supernova Winds on the Tidal Stirring of Disky Dwarfs: Enhanced Transformation into Dwarf Spheroidals

Journal Article · Fri Feb 10 04:00:00 EST 2017 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8213/AA5B8F· OSTI ID:22654543

Kazantzidis, Stelios ^[1]; Mayer, Lucio ^[2]; Callegari, Simone ^[3]; Dotti, Massimo ^[4]

---

1. Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, 15784 Zografos, Athens (Greece)
2. Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich, CH-8057 Zürich (Switzerland)
3. Anthropology Institute and Museum, University of Zürich, CH-8057 Zürich (Switzerland)
4. Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy)

A conclusive model for the formation of dwarf spheroidal (dSph) galaxies still remains elusive. Owing to their proximity to the massive spirals Milky Way (MW) and M31, various environmental processes have been invoked to explain their origin. In this context, the tidal stirring model postulates that interactions with MW-sized hosts can transform rotationally supported dwarfs, resembling present-day dwarf irregular (dIrr) galaxies, into systems with the kinematic and structural properties of dSphs. Using N -body+SPH simulations, we investigate the dependence of this transformation mechanism on the gas fraction, f {sub gas}, in the disk of the progenitor dwarf. Our numerical experiments incorporate for the first time the combined effects of radiative cooling, ram-pressure stripping, star formation, supernova (SN) winds, and a cosmic UV background. For a given orbit inside the primary galaxy, rotationally supported dwarfs with gas fractions akin to those of observed dIrrs ( f {sub gas} ≳ 0.5), demonstrate a substantially enhanced likelihood and efficiency of transformation into dSphs relative to their collisionless ( f {sub gas} = 0) counterparts. We argue that the combination of ram-pressure stripping and SN winds causes the gas-rich dwarfs to respond more impulsively to tides, augmenting their transformation. When f {sub gas} ≳ 0.5, disky dwarfs on previously unfavorable low-eccentricity or large-pericenter orbits are still able to transform. On the widest orbits, the transformation is incomplete; the dwarfs retain significant rotational support, a relatively flat shape, and some gas, naturally resembling transition-type systems. We conclude that tidal stirring constitutes a prevalent evolutionary mechanism for shaping the structure of dwarf galaxies within the currently favored CDM cosmological paradigm.

• OSTI ID: 22654543
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 836; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DWARF STARS
INTERACTIONS
MILKY WAY
ORBITS
RADIATIVE COOLING
SIMULATION
STARS
STELLAR WINDS
STIRRING
STRIPPING
SUPERNOVAE