WEAVE Apertif

Group-driven galaxy evolution with WEAVE-Apertif

Kelley Hess

WEAVE-Apertif will observe approximately 500 Apertif HI detected galaxies with the large integral field unit (LIFU) on the WEAVE spectrograph mounted on the William Herschel Telescope.  The resolved stellar populations, combined with resolved HI maps from Apertif of galaxy groups and group member galaxies will permit a detailed study of the mechanisms driving gas loss in galaxies and the subsequent timescales for quenching star formation. 

Goals of Group-driven Galaxy Evolution:

  • Gas removal mechanisms ➔ Use HI morphologies across a range of group halo masses to understand in which group environments different physical processes are responsible for removing gas from galaxy and contributing to galaxy quenching: i.e. tidal interactions vs ram pressure stripping vs starvation.
  • Quantifying the amount of intragroup HI ➔ Wide-field HI observations and mosaics of galaxy groups regularly reveal an unexpected amount of intragroup HI, presumably lost through a combination of  the mechanisms above.  Using a well defined group sample, we would place lower limits on the amount of neutral HI in intragroup environment.  This is important to understand the build-up, as well as the conditions of the warm/hot intragroup medium. 
  • Timescales of galaxy quenching ➔ Combining the HI content/deficiency/morphology and galaxy group halo environment/radius with the resolved star formation history and stellar population, we will estimate the timescales of gas loss and quenching of star formation in different environments and quantify the stellar signatures caused by different gas removal mechanisms.

WEAVE-Apertif has three main science goals.  In particular, Group-driven Galaxy Evolution will be linked to the first main science goal, but we mention all three here for completeness:

1. Understanding the nature of galaxy bimodality :  study the fueling and quenching of star formation in galaxies, and how that leads to the bimodality of the galaxy population we see today.  The WA survey will:

  • Observe ~500 HI detected galaxies at z<0.03 with the LIFU at R=2500.  This sample will be unbiased with respect to absolute magnitude, color, but chosen based on their HI properties, with half being undisturbed, and half showing signs in HI of interaction with their environment;
  • Observe with good enough signal-to-noise in the stellar continuum to characterize stellar populations;
  • Will be the only dedicated LIFU follow-up of an HI selected sample, and provide the largest number of galaxies for which complementary spatially resolved stellar, ionized gas, and cold neutral gas properties exists.

2. Disk galaxy mass dissection: accurately measure the dark matter component of disks, and its distribution.  This will be achieved by:

  • Observing 50-100 HI detected ~face-on galaxies with the LIFU at high resolution, R=10,000;
  • Observe with good enough signal-to-noise in the stellar continuum to measure stellar velocity dispersions.

3. Secular galaxy evolution: study the conditions, distribution, and kinematics of the gas and stars in the central regions of galaxies to understand how bars, spiral arms, etc, contribute to the scattering of stars and consumption of gas within galaxies. 

Design: Kuenst.    Development: Dripl.    © 2020 ASTRON