SAGES Legacy Unifying Globulars and GalaxieS Survey

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SAGES Legacy Unifying Globulars and GalaxieS Survey
SLUGGS galaxies.png
Colour thumbnails of the 25 galaxies in the SLUGGS survey.
Website sluggs.swin.edu.au
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The SLUGGS (SAGES Legacy Unifying Globulars and GalaxieS) survey is an astronomical survey of 25 (and 3 `bonus') nearby early-type (E and S0) galaxies. This survey uses a combination of imaging from Subaru/Suprime-Cam and spectroscopy from Keck/DEIMOS to investigate the chemo-dynamical properties of both the diffuse starlight and the globular cluster systems of the target galaxies. Pilot data for the survey was obtained in 2006 and data acquisition was completed in 2017. [1]

Contents

The SLUGGS project was so named in honor of the banana slug mascot of the University of California, Santa Cruz.

SAGES

SAGES (Study of the Astrophysics of Globular Clusters in Extragalactic Systems) is an international network of researchers investigating the formation and evolution of globular clusters and their host galaxies, using observational facilities around the world, particularly the Keck and Subaru telescopes. [2] It was founded by Jean Brodie, Duncan Forbes, Aaron Romanowsky and Jay Strader.

Method

Deep wide-field imaging from Subaru/Suprime-Cam is used to identify and measure the positions of candidate globular clusters around each survey galaxy. Several (up to 6) DEIMOS masks are then created which include slits corresponding to the locations of globular clusters, galaxy starlight and random background sky locations in the outer parts of the mask. The DEIMOS spectrograph, on the Keck telescope, is centred on wavelengths around the Calcium Triplet lines (~850 nm). After a typical 2 hour exposure per mask, spectra of globular clusters and galaxy starlight is obtained. Using a technique called SKiMS (Stellar Kinematics from Multiple Slits) it is possible to extract the kinematics (and metallicity) of galaxy starlight out to 3 effective radii. Equivalent data for the globular clusters is obtained out to ~10 effective radii. The DEIMOS instrument has the advantages of being a stable, high throughput, wide-field spectrograph coupled with excellent velocity resolution (~12 km/s) on a 10m telescope. This technique effectively uses DEIMOS as a pseudo wide area integral field unit. [3]

Survey selection

The 25 target galaxies are chosen to be representative (i.e. cover the range of basic galaxy parameters and environments) of nearby (distance < 27 Mpc) early type (E and S0) galaxies. The survey also includes 3 `bonus’ galaxies which have been observed during times that the main sample galaxies are not available. All galaxies are accessible from the northern hemisphere. Although only a small sample, the data reach to large galactocentric radii with excellent velocity resolution and S/N compared to other surveys. [4]

Key science questions

  1. What are the basic, global chemo-dynamical properties of early type galaxies?
  2. What is the distribution of dark matter in early-type galaxies?
  3. How are the outer regions of early-type galaxies assembled?
  4. How does assembly depend on mass, environment, and other variables?
  5. Do the observations agree with theoretical models of galaxy formation?

Target galaxies

NGC 720, NGC 821, NGC 1023, NGC 1400, NGC 1407, NGC 2768, NGC 2974, NGC 3115, NGC 3377, NGC 3608, NGC 4111, NGC 4278, NGC 4365, NGC 4374, NGC 4459, NGC 4473, NGC 4474, NGC 4486, NGC 4494, NGC 4526, NGC 4564, NGC 4649, NGC 4697, NGC 5846, NGC 7457.

The bonus galaxies are NGC 3607, NGC 4594 and NGC 5866.

Further reading

Notes

A complete list of publications using SLUGGS survey data can be found here.

Related Research Articles

<span class="mw-page-title-main">Lenticular galaxy</span> Class of galaxy between an elliptical galaxy and a spiral galaxy

A lenticular galaxy is a type of galaxy intermediate between an elliptical and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. Lenticular galaxies are disc galaxies that have used up or lost most of their interstellar matter and therefore have very little ongoing star formation. They may, however, retain significant dust in their disks. As a result, they consist mainly of aging stars. Despite the morphological differences, lenticular and elliptical galaxies share common properties like spectral features and scaling relations. Both can be considered early-type galaxies that are passively evolving, at least in the local part of the Universe. Connecting the E galaxies with the S0 galaxies are the ES galaxies with intermediate-scale discs.

<span class="mw-page-title-main">NGC 5866</span> Galaxy in the constellation Draco

NGC 5866 is a relatively bright lenticular galaxy in the constellation Draco. NGC 5866 was most likely discovered by Pierre Méchain or Charles Messier in 1781, and independently found by William Herschel in 1788. Measured orbital velocities of its globular cluster system imply that dark matter makes up only 34±45% of the mass within 5 effective radii, a notable paucity.

<span class="mw-page-title-main">Dwarf galaxy</span> Small galaxy composed of up to several billion stars

A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is sometimes classified as a dwarf galaxy; others consider it a full-fledged galaxy. Dwarf galaxies' formation and activity are thought to be heavily influenced by interactions with larger galaxies. Astronomers identify numerous types of dwarf galaxies, based on their shape and composition.

<span class="mw-page-title-main">NGC 4526</span> Lenticular galaxy in the constellation Virgo

NGC 4526 is a lenticular galaxy with an embedded dusty disc, located approximately 55 million light-years from the Solar System in the Virgo constellation and discovered on 13 April 1784 by William Herschel.

<span class="mw-page-title-main">NGC 3607</span> Galaxy in the constellation Leo

NGC 3607 is a small but fairly bright lenticular galaxy in the equatorial constellation of Leo, about 2.5° south of the prominent star Delta Leonis. The galaxy was discovered March 14, 1784 by William Herschel. Dreyer described it as "very bright, large, round, very much brighter middle, 2nd of 3". It is located at a distance of 73 million light years and is receding with a radial velocity of 930 km/s. The galaxy lies southwest of NGC 3626 at an angular separation of ~50′. It occupies the center of the Leo II Group of galaxies, forming one of its two brightest members – the other being NGC 3608. It is a member of the NGC 3607 Group of galaxies, which is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster.

<span class="mw-page-title-main">NGC 6352</span> Globular cluster in the constellation Ara

NGC 6352 is a globular cluster of stars in the southern constellation of Ara, located approximately 18.3 kly from the Sun. It was discovered by Scottish astronomer James Dunlop on May 14, 1826. The cluster has a Shapley–Sawyer Concentration Class of XI:. A telescope with a 15 cm (5.9 in) aperture is required to resolve the stars within this loose cluster.

<span class="mw-page-title-main">Ultra diffuse galaxy</span> Extremely low luminosity galaxy

An ultra diffuse galaxy (UDG) is an extremely low luminosity galaxy, the first example of which was discovered in the nearby Virgo Cluster by Allan Sandage and Bruno Binggeli in 1984. These galaxies have been studied for many years prior to their renaming in 2015. Their lack of luminosity is due to the lack of star-forming gas, which results in these galaxies being reservoirs of very old stellar populations.

<span class="mw-page-title-main">Dragonfly 44</span> Galaxy in constellation Coma Berenices

Dragonfly 44 is an ultra diffuse galaxy in the Coma Cluster. This galaxy is well-known because observations of the velocity dispersion in 2016 suggested a mass of about one trillion solar masses, about the same as the Milky Way. This mass was consistent with a count of about 90 and 70 globular clusters observed around Dragonfly 44 in two different studies.

<span class="mw-page-title-main">NGC 4494</span> Galaxy in the constellation Coma Berenices

NGC 4494 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 45 million light years from Earth, which, given its apparent dimensions, means that NGC 4494 is about 60,000 light years across. It was discovered by William Herschel in 1785.

<span class="mw-page-title-main">NGC 4473</span> Galaxy in the constellation Coma Berenices

NGC 4473 is an elliptical galaxy located about 50 million light-years away in the constellation of Coma Berenices. It was discovered by astronomer William Herschel on April 8, 1784. NGC 4473 has an inclination of about 71°. NGC 4473 is a member of a chain of galaxies called Markarian's Chain which is part of the larger Virgo Cluster of galaxies.

<span class="mw-page-title-main">NGC 3311</span> Galaxy in the constellation Hydra

NGC 3311 is a supergiant elliptical galaxy located about 190 million light-years away in the constellation Hydra. The galaxy was discovered by astronomer John Herschel on March 30, 1835. NGC 3311 is the brightest member of the Hydra Cluster and forms a pair with NGC 3309 which along with NGC 3311, dominate the central region of the Hydra Cluster.

<span class="mw-page-title-main">NGC 720</span> Galaxy in the constellation Cetus

NGC 720 is an elliptical galaxy located in the constellation Cetus. It is located at a distance of circa 80 million light years from Earth, which, given its apparent dimensions, means that NGC 720 is about 110,000 light years across. It was discovered by William Herschel on October 3, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies about three and a half degrees south and slightly east from zeta Ceti.

<span class="mw-page-title-main">NGC 1380</span> Galaxy in the constellation Fornax

NGC 1380 is a lenticular galaxy located in the constellation Fornax. It is located at a distance of circa 60 million light years from Earth, which, given its apparent dimensions, means that NGC 1380 is about 85,000 light years across. It was discovered by James Dunlop on September 2, 1826. It is a member of the Fornax Cluster.

<span class="mw-page-title-main">NGC 5846</span> Galaxy in the constellation Virgo

NGC 5846 is an elliptical galaxy located in the constellation Virgo. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 5846 is about 110,000 light years across. It was discovered by William Herschel on February 24, 1786. It lies near 110 Virginis and is part of the Herschel 400 Catalogue. It is a member of the NGC 5846 Group of galaxies, itself one of the Virgo III Groups strung out to the east of the Virgo Supercluster of galaxies.

<span class="mw-page-title-main">NGC 4278</span> Galaxy in the constellation Coma Berenices

NGC 4278 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 55 million light years from Earth, which, given its apparent dimensions, means that NGC 4278 is about 65,000 light years across. It was discovered by William Herschel on March 13, 1785. NGC 4278 is part of the Herschel 400 Catalogue and can be found about one and 3/4 of a degree northwest of Gamma Comae Berenices even with a small telescope.

<span class="mw-page-title-main">NGC 4318</span> Galaxy in the constellation Virgo

NGC 4318 is a small lenticular galaxy located about 72 million light-years away in the constellation Virgo. It was discovered by astronomer John Herschel on January 18, 1828. NGC 4318 is a member of the Virgo W′ group, a group of galaxies in the background of the Virgo Cluster that is centered on the giant elliptical galaxy NGC 4365.

<span class="mw-page-title-main">NGC 4365</span> Elliptical galaxy in the constellation Virgo

NGC 4365 is an elliptical galaxy located in the constellation Virgo. It was discovered by William Herschel on April 13, 1784.

<span class="mw-page-title-main">NGC 3608</span>

NGC 3608 is an elliptical galaxy located in the constellation Leo. It was discovered by William Herschel on March 14, 1784.

<span class="mw-page-title-main">NGC 3605</span>

NGC 3605 is an elliptical galaxy located in the constellation Leo. It was discovered on March 14, 1784 by the astronomer William Herschel.

References

  1. ↑ SLUGGS survey. "SLUGGS Survey".
  2. ↑ "Home page". SAGES. Retrieved 1 June 2019.
  3. ↑ Arnold, Jacob A.; Romanowsky, Aaron J.; Brodie, Jean P.; Forbes, Duncan A.; Strader, Jay; Spitler, Lee R.; Foster, Caroline; Blom, Christina; Kartha, Sreeja S.; Pastorello, Nicola; Pota, Vincenzo; Usher, Christopher; Woodley, Kristin A. (30 July 2014). "The Sluggs Survey: Wide-Field Stellar Kinematics of Early-Type Galaxies". The Astrophysical Journal. 791 (2): 80. arXiv: 1310.2607 . Bibcode:2014ApJ...791...80A. doi:10.1088/0004-637X/791/2/80. S2CID   54001092.
  4. ↑ Brodie, Jean P.; Romanowsky, Aaron J.; Strader, Jay; Forbes, Duncan A.; Foster, Caroline; Jennings, Zachary G.; Pastorello, Nicola; Pota, Vincenzo; Usher, Christopher; Blom, Christina; Kader, Justin; Roediger, Joel C.; Spitler, Lee R.; Villaume, Alexa; Arnold, Jacob A.; Kartha, Sreeja S.; Woodley, Kristin A. (5 November 2014). "The Sages Legacy Unifying Globulars and Galaxies Survey (Sluggs): Sample Definition, Methods, and Initial Results". The Astrophysical Journal. 796 (1): 52. arXiv: 1405.2079 . Bibcode:2014ApJ...796...52B. doi:10.1088/0004-637X/796/1/52. S2CID   54189744.
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