The data for the SAMI Galaxy Survey is being collected using SAMI, the Sydney-Australian-Astronomical-Observatory Multi-object Integral-Field Spectrograph. The SAMI instrument was on the 4-meter Anglo-Australian Telescope at Siding Spring Observatory. Integral-field spectroscopy (IFS) allows a unique “3D” view of how stars and gas zoom around inside distant galaxies because we collect dozens of spectra across the entire face of each galaxy, which not only tells us what the stars are made of in the galaxy, but also whether the stars and gas are moving towards us or away from us.

The SAMI Galaxy Survey began in March 2013 and has just completed collecting spectra of 3068 galaxies across a large range of environments.

The key science goals of the SAMI Survey are to answer the following questions:

What is the physical role of environment in galaxy evolution?
What is the relationship between stellar mass growth (stars forming and evolving) and angular momentum development (motion of stars, gas and dark matter) in galaxies?
How does gas get into and out of galaxies, and how does this drive star formation?

The Hector instrument will replace SAMI – increasing the power of SAMI in terms of the spectral resolution, spatial sampling and galaxy number. Hector will be commissioned on the Anglo-Australian Telescope (AAT) at the end of 2020. The combination of SAMI/Hector and the ASKAP Surveys will track how and where galaxies build their matter and angular momentum, as well as how the chemical elements are spread across galaxies.

The SAMI Survey

The SAMI Survey is the first 3D spectroscopy sample that is sufficiently large to disentangle the competing roles of galaxy mass and environment. As a result, the team can address the following three questions:

What is the physical role of environment in galaxy evolution?
What is the interplay between gas flows and galaxy evolution?
How are mass and angular momentum built up in galaxies.

Data Release 1

Data Release 1 (DR1) includes observations and ionised gas property measurements for 772 galaxies.

The galaxies are displayed by stellar mass and star-formation rate. Survey highlights include:

Starburst in a Dwarf Galaxy – intense star-formation activity is detected on the edge of a dwarf galaxy, responsible for 70% of the galaxy’s Hα luminosity.
Wind Dominated Galaxy – evidence for huge galactic-scale winds in edge-on spiral galaxies driven by massive bursts of star formation.
Seyfert 1 Galaxy – A supermassive black hole detected in a small, intensely bright galaxy with weak spiral arms.
Kinematically Offset AGN? – we have discovered galaxies where the gas is moving in a different way to the stars. This unusual effect could be caused by recent galaxy collisions or shock heating of gas falling into the central galaxy regions.

Data Release 2

Data Release 2 (DR2) includes spectral cubes, absorption line and emission line products for 1559 galaxies.

The Figure on the right shows the stellar metallicity (amount of chemical elements locked up in stars) versus the dynamical mass of the galaxies. Survey highlights include:

Disturbed Gas Disk in a Rotating Early-Type Dwarf Galaxy – a low-mass early-type galaxy with regular star rotation, but without a dispersion-dominated central bulge.
Asymmetric Velocity Field in a Barred Spiral Galaxy – this galaxy is a prime example of how a central bar and spiral arms affect both the motions of stars and interstellar gas within galaxies.
Polar Ring Galaxy – this galaxy is an intriguing special case of where the stars and gas are not in the same plane – the stellar disk rotates North-South, but is surrounded by an East-West ring of gas and dust forming stars.
Embedded Disk in a Massive Early-Type Galaxy – this galaxy has a peculiar profile that points to a massive round elliptical galaxy with a thin disk embedded inside.

Data Release 3

The SAMI Galaxy Survey Data Release 3 (DR3) includes:

reduced observations,
stellar population,
stellar kinematic and
ionised gas property measurements

for the full sample of 3068 galaxies. This constitutes all galaxies observed in the GAMA regions and Cluster regions during the survey that was completed in May 2018.

DR3 is fully described in Croom et al. (2021). The data are provided online through Australian Astronomical Optics’ Data Central.

The Hector instrument

Hector is the next major dark-time instrument for the AAT and is a multi integral-field-unit spectrograph aimed at obtaining a low-redshift galaxy survey of up to 30,000 galaxies, with 90% imaged out to 2 effective radii.

Hector will decipher the diversity of galaxies through understanding the physical basis for their individuality.

The key science questions for this instrument include:

how do galaxies build up mass and angular momentum?
how is star formation and nuclear activity affected by environment?
what is the role of feedback, and how does large-scale environment modulate galaxy growth through tidal torques and gas accretion?

A new, innovative robotic system will position magnets across the field plate which will rotate the hexabundles in 3 axes to match telecentricity and ferule positioning, which will improve throughput over the existing 2dF facility. Observers will put the configured plate onto the telescope and attach the 21 hexabundles. One plate can be being configured by the robot while another is observing.