Dragonfly 44

Last updated
Dragonfly 44
Df44-BW-high-contrast.png
Hubble Space Telescope view of the galaxy Dragonfly 44
Observation data (J2000 epoch)
Constellation Coma Berenices
Right ascension 13h 00m 58.0s [1]
Declination +26° 58′ 35″ [1]
Redshift ~0.023
Heliocentric radial velocity 6280 ± 120 km/s
Distance ~100 Mpc (~330 Mly)
Group or cluster Coma Cluster
Apparent magnitude  (V)21 mags; or 19.4 mags [2]
Apparent magnitude  (B)22
Absolute magnitude  (V)-16.1 mag [2]
Characteristics
Mass ~1.6×1011  M☉
Apparent size  (V)10 x 35 arcsec
Other designations
SDSS J130057.98+265839.6, SDSS J130058.17+265836.1 , SDSS J130058.21+265829.3

Dragonfly 44 is an ultra diffuse galaxy in the Coma Cluster. [1] [3] [2] [4] 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.

Contents

Later, spatially resolved kinematics measured a mass of about 160 billion solar masses, six times less than early mass measurements and one order of magnitude less than the Milky Way's mass. [5] The most recent work found 20 globular clusters around the galaxy, which is consistent with the current mass measurement. [6] [7] The lack of X-ray emission from the galaxy and its surroundings also shows that the number of globular clusters cannot be as many as was claimed before. [8]

The galaxy emits only 1% of the light emitted by the Milky Way. [9] The galaxy was discovered with the Dragonfly Telephoto Array. [10]

Early study

To determine the amount of dark matter in this galaxy, in 2016, astronomers used the DEIMOS instrument installed on Keck II to measure the velocities of stars for 33.5 hours for six nights so they could determine the galaxy's mass. The scientists then used the Gemini Multi-Object Spectrograph on the 8-m Gemini North telescope to reveal a halo of spherical clusters of stars around the galaxy's core. [11] Following this observation, in August 2016, astronomers reported that this galaxy might be made almost entirely of dark matter. [12] [13] [14]

See also

Related Research Articles

<span class="mw-page-title-main">Messier 87</span> Elliptical galaxy in the Virgo Galaxy Cluster

Messier 87 is a supergiant elliptical galaxy in the constellation Virgo that contains several trillion stars. One of the largest and most massive galaxies in the local universe, it has a large population of globular clusters—about 15,000 compared with the 150–200 orbiting the Milky Way—and a jet of energetic plasma that originates at the core and extends at least 1,500 parsecs, traveling at a relativistic speed. It is one of the brightest radio sources in the sky and a popular target for both amateur and professional astronomers.

<span class="mw-page-title-main">Intermediate-mass black hole</span> Class of black holes with a mass range of 100 to 100000 solar masses

An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range of tens to tens thousand (102–105) solar masses: significantly higher than stellar black holes but lower than the tens thousand to hundreds trillion (105–1015) solar mass supermassive black holes. Several IMBH candidate objects have been discovered in the Milky Way galaxy and others nearby, based on indirect gas cloud velocity and accretion disk spectra observations of various evidentiary strength.

<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">Dwarf spheroidal galaxy</span> Low-luminosity galaxy of old stars & little dust

A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and as systems that are companions to the Andromeda Galaxy (M31). While similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust or recent star formation, they are approximately spheroidal in shape and generally have lower luminosity.

A dark galaxy is a hypothesized galaxy with no stars. They received their name because they have no visible stars but may be detectable if they contain significant amounts of gas. Astronomers have long theorized the existence of dark galaxies, but there are no confirmed examples to date. Dark galaxies are distinct from intergalactic gas clouds caused by galactic tidal interactions, since these gas clouds do not contain dark matter, so they do not technically qualify as galaxies. Distinguishing between intergalactic gas clouds and galaxies is difficult; most candidate dark galaxies turn out to be tidal gas clouds. The best candidate dark galaxies to date include HI1225+01, AGC229385, and numerous gas clouds detected in studies of quasars.

<span class="mw-page-title-main">Satellite galaxy</span> Galaxy that orbits a larger galaxy due to gravitational attraction

A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy. Satellite galaxies and their constituents are bound to their host galaxy, in the same way that planets within the Solar System are gravitationally bound to the Sun. While most satellite galaxies are dwarf galaxies, satellite galaxies of large galaxy clusters can be much more massive. The Milky Way is orbited by about fifty satellite galaxies, the largest of which is the Large Magellanic Cloud.

The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.

Pisces II is a dwarf spheroidal galaxy situated in the Pisces constellation and discovered in 2010 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 180 kpc (kiloparsecs) from the Sun. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elongated shape with the half-light radius of about 60 pc and ratio of the axis of about 5:3.

<span class="mw-page-title-main">NGC 1277</span> Galaxy in the constellation Perseus

NGC 1277 is a lenticular galaxy in the constellation of Perseus. It is a member of the Perseus Cluster of galaxies and is located approximately 73 Mpc (megaparsecs) or 220 million light-years from the Milky Way. It has an apparent magnitude of about 14.7. It was discovered on December 4, 1875 by Lawrence Parsons, 4th Earl of Rosse.

<span class="mw-page-title-main">NGC 1052</span> Elliptical galaxy in the constellation Cetus

NGC 1052 is an elliptical galaxy in the constellation Cetus. It was discovered on January 10, 1785 by the astronomer William Herschel. It is a member of the eponymous NGC 1052 Group.

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

An ultra diffuse galaxy (UDG), or Dark galaxy, 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.

Triangulum II is a dwarf galaxy close to the Milky Way Galaxy. Like other dwarf spheroidal galaxies, its stellar population is very old: the galaxy was quenched before 11.5 billion years ago. It contains only 1000 stars, yet is quite massive, having a solar mass to light ratio of 3600. This is an unusually high mass for such a small galaxy.

Crater 2 is a low-surface-brightness dwarf satellite galaxy of the Milky Way, located approximately 380,000 ly from Earth. Its discovery in 2016 revealed significant gaps in astronomers' understanding of galaxies possessing relatively small half-light diameters and suggested the possibility of many undiscovered dwarf galaxies orbiting the Milky Way. Crater 2 was identified in imaging data from the VST ATLAS survey.

The Eridanus II Dwarf is a low-surface brightness dwarf galaxy in the constellation Eridanus. Eridanus II was independently discovered by two groups in 2015, using data from the Dark Energy Survey. This galaxy is probably a distant satellite of the Milky Way. Eridanus II contains a centrally located globular cluster; and is the smallest, least luminous galaxy known to contain a globular cluster. Crnojević et al., 2016. Eridanus II is significant, in a general sense, because the widely accepted Lambda CDM cosmology predicts the existence of many more dwarf galaxies than have yet been observed. The search for just such bodies was one of the motivations for the ongoing Dark Energy Survey observations. Eridanus II has special significance because of its apparently stable globular cluster. The stability of this cluster, near the center of such a small, diffuse, galaxy places constraints on the nature of dark matter.

The Dragonfly Telephoto Array is a ground-based optical telescope array developed at the Dunlap Institute for Astronomy & Astrophysics of the University of Toronto in Canada. The array uses a combination of telephoto lenses to observe extragalactic objects. Its main purpose is to take images of ultra-low surface brightness galaxies at visible wavelengths of light. It is well suited for this purpose because its lenses have specially-coated optical glass that reduces scattered light.

<span class="mw-page-title-main">NGC 1052-DF2</span> Ultra diffuse galaxy in the constellation Cetus

NGC 1052-DF2 is an ultra diffuse galaxy (UDG) identified in a wide-field imaging survey of the NGC 1052 group by the Dragonfly Telephoto Array. It has been proposed that the galaxy contains little or no dark matter, the first such discovery. On 20 March 2019, a follow-up study announcing the discovery of a second UDG lacking dark matter, NGC 1052-DF4, was published.

<span class="mw-page-title-main">Gaia Sausage</span> Remains galaxy merger in the Milky Way

The Gaia Sausage or Gaia Enceladus is the remains of a dwarf galaxy that merged with the Milky Way about 8–11 billion years ago. At least eight globular clusters were added to the Milky Way along with 50 billion solar masses of stars, gas and dark matter. It represents the last major merger of the Milky Way.

<span class="mw-page-title-main">NGC 7492</span> Globular cluster in the constellation Aquarius

NGC 7492 is a globular cluster in the constellation Aquarius. It was discovered by the astronomer William Herschel on September 20, 1786. It resides in the outskirts of the Milky Way, about 80,000 light-years away, more than twice the distance between the Sun and the center of the galaxy, and is a benchmark member of the outer galactic halo. The cluster is immersed in, but does not kinematically belong to, the Sagittarius Stream.

References

  1. 1 2 3 Van Dokkum, Pieter; et al. (7 January 2015). "Forty-Seven Milky Way-sized, Extremely Diffuse Galaxies in the Coma-Cluster". The Astrophysical Journal Letters. 798 (2): L45. arXiv: 1410.8141 . Bibcode:2015ApJ...798L..45V. doi:10.1088/2041-8205/798/2/L45. S2CID   119279968.
  2. 1 2 3 Van Dokkum, Pieter; et al. (1 May 2015). "Spectroscopic confirmation of the existence of large, diffuse galaxies in the coma cluster". The Astrophysical Journal Letters . 804 (1): L26. arXiv: 1504.03320 . Bibcode:2015ApJ...804L..26V. doi:10.1088/2041-8205/804/1/L26. S2CID   54664026.
  3. ↑ "Scientists discover the fluffiest galaxies". phys.org. 14 May 2015.
  4. ↑ "Dragonfly 44: Ultra-Diffuse Galaxy Made Mostly of Dark Matter". Sci.News. 25 August 2016. Retrieved 21 January 2024.
  5. ↑ Van Dokkum, Pieter; Wasserman, Asher; Danieli, Shany; Abraham, Roberto; Brodie, Jean; Conroy, Charlie; Forbes, Duncan A.; Martin, Christopher; Matuszewski, Matt; Romanowsky, Aaron J.; Villaume, Alexa (2019). "Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits, Peter van Dokkum et al. 2019". The Astrophysical Journal. 880 (2): 91. arXiv: 1904.04838 . doi: 10.3847/1538-4357/ab2914 . S2CID   119185644.
  6. ↑ Saifollahi, Teymoor; Trujillo, Ignacio; Beasley, Michael A.; Peletier, Reynier F.; Knapen, Johan H. (2020). ""The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies", Saifollahi et al. 2020". Monthly Notices of the Royal Astronomical Society. 502 (4): 5921–5934. arXiv: 2006.14630 . doi: 10.1093/mnras/staa3016 . S2CID   220127887.
  7. ↑ "The puzzle of the strange galaxy made of 99.99% dark matter is solved". Instituto de Astrofísica de Canarias. 13 October 2020. Retrieved 21 January 2024.
  8. ↑ Bogdan, Akos (2020). ""The American Astronomical Society, find out more The Institute of Physics, find out more The Archetypal Ultra-diffuse Galaxy, Dragonfly 44, Is not a Dark Milky Way", Bogdan 2020". The Astrophysical Journal Letters. arXiv: 2009.07846 . doi: 10.3847/2041-8213/abb886 . S2CID   221761669.
  9. ↑ Crosswell, Ken (26 July 2016). "The Milky Way's dark twin revealed". Nature News. Retrieved 30 July 2016.
  10. ↑ Rachel Feltman (25 August 2016). "A new class of galaxy has been discovered, one made almost entirely of dark matter". The Washington Post .
  11. ↑ Byrd, D. (30 August 2016). "A galaxy made of 99.9% dark matter". EarthSky Communications. Retrieved 21 January 2024.
  12. ↑ Van Dokkum, Pieter; et al. (25 August 2016). "A High Stellar Velocity Dispersion and ~100 Globular Clusters For The Ultra-Diffuse Galaxy Dragonfly 44". The Astrophysical Journal Letters . 828 (1): L6. arXiv: 1606.06291 . Bibcode:2016ApJ...828L...6V. doi: 10.3847/2041-8205/828/1/L6 . S2CID   1275440.
  13. ↑ Hall, Shannon (25 August 2016). "Ghost galaxy is 99.99 per cent dark matter with almost no stars". New Scientist . Retrieved 27 August 2016.
  14. ↑ Feltman, Rachael (26 August 2016). "A new class of galaxy has been discovered, one made almost entirely of dark matter". The Washington Post . Retrieved 26 August 2016.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.