Blue blob

Last updated

A blue blob is a type of stellar system found in intergalactic space. Blue blobs usually consist of several clusters and star-forming regions within a few kpc, with no sign of an older stellar population. There is nothing in the vicinity of these blue blobs, as they are surrounded by intergalactic space, sometimes for hundreds of kiloparsecs. Currently, 5 blue blobs are known, all located in the Virgo Cluster. Blue blobs are also sometimes known as Ram Pressure Dwarfs, due to their formation likely being due to ram-pressure stripping of gas from nearby galaxies, which drifted through intergalactic space and then went through starburst, producing these blue blobs. [1]

Contents

Discovery

The first blue blob discovered was SECCO 1, first identified as an interesting object in 2015 [2] and then later identified as the first blue blob (or what could be described as a blue blob) in 2016. [3] SECCO 1 is also known as AGC 226067, and it was identified as a gas cloud in a 2007 Arecibo survey for intergalactic H I clouds. Later, 4 other such blue blobs were identified in the Virgo Cluster. [1] A recent Zooniverse project looking for blue blobs and dwarf spheroidal galaxies in the Fornax Cluster and Virgo Cluster will probably identify some more blue blobs. [4]

Properties

Blue blobs consist of several clumps of star-forming areas, filled with young blue stars, clusters and H II regions. Their stellar masses are very small, only about 50,000 to 100,000 M☉. The oldest stellar populations in the observed blue blobs are no older than 160 million years old in the oldest case, to just 50 million years old in the youngest. However, it is possible that there exist stars which formed before starburst began, and they may be detectable with observations from JWST. [1]

Metallicity

The observed blue blobs have extremely high metallicities for their small mass. They have O/H values ranging from 8.3 to 8.7, which is in the regime of the metallicities of large galaxies such as the LMC and the Milky Way, or in other words, a significant percentage of that of the Milky Way. This is much higher than the metallicities of galaxies of its mass, which made it hard to explain their formation. The only source of high-metallicity material in the area were the large galaxies of the Virgo Cluster, which means that the blue blobs could not have formed on their own, but must have been formed from material from these other galaxies. [1]

Formation hypothesis

This means that the blue blobs couldn’t have formed on their own, and are likely composed of high-metallicity gas stripped off large, infalling galaxies (only galaxies which are new members of the Virgo Cluster) via ram pressure stripping. Hence they can also be thought of as ‘ram pressure dwarfs’. After some time floating in intergalactic space, these blobs of metal-rich gas would quickly go through a starburst phase, producing the blue blobs. [1]

Related Research Articles

<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">Messier 86</span> Elliptical galaxy in the constellation Virgo

Messier 86 is an elliptical or lenticular galaxy in the constellation Virgo. It was discovered by Charles Messier in 1781. M86 lies in the heart of the Virgo Cluster of galaxies and forms a most conspicuous group with another large galaxy known as Messier 84. It displays the highest blue shift of all Messier objects, as it is, net of its other vectors of travel, approaching the Milky Way at 244 km/s. This is due to both galaxies falling roughly towards the center of the Virgo cluster from opposing ends.

<span class="mw-page-title-main">Messier 90</span> Galaxy in the constellation Virgo

Messier 90 is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away[a] in the constellation Virgo. It was discovered by Charles Messier in 1781.

The Canis Major Overdensity or Canis Major Dwarf Galaxy is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major.

<span class="mw-page-title-main">Ram pressure</span> Pressure due to movement through a fluid medium

Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as

<span class="mw-page-title-main">NGC 1569</span> Galaxy in the constellation Camelopardalis

NGC 1569 is a dwarf irregular galaxy in Camelopardalis. The galaxy is relatively nearby and consequently, the Hubble Space Telescope can easily resolve the stars within the galaxy. The distance to the galaxy was previously believed to be only 2.4 Mpc. However, in 2008 scientists studying images from Hubble calculated the galaxy's distance at nearly 11 million light-years away, about 4 million light-years farther than previously thought, meaning it is a member of the IC 342 group of galaxies.

<span class="mw-page-title-main">Wolf–Lundmark–Melotte</span> Irregular galaxy in the Local Group

The Wolf–Lundmark–Melotte Galaxy (WLM) is a barred irregular galaxy discovered in 1909 by Max Wolf, located on the outer edges of the Local Group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melotte in 1926. It is in the constellation Cetus.

<span class="mw-page-title-main">NGC 4216</span> Galaxy in the constellation Virgo

NGC 4216 is a metal-rich intermediate spiral galaxy located not far from the center of the Virgo Cluster of galaxies, roughly 55 million light-years away. It is seen nearly edge-on.

<span class="mw-page-title-main">Eyes Galaxies</span> Pair of galaxies in the constellation Virgo

The Eyes Galaxies are a pair of galaxies about 52 million light-years away in the constellation Virgo. The pair are members of the string of galaxies known as Markarian's Chain.

<span class="mw-page-title-main">NGC 4449</span> Galaxy in the constellation Canes Venatici

NGC 4449, also known as Caldwell 21, is an irregular Magellanic type galaxy in the constellation Canes Venatici, being located about 13 million light-years away. It is part of the M94 Group or Canes Venatici I Group that is relatively close to the Local Group hosting our Milky Way galaxy.

<span class="mw-page-title-main">Pea galaxy</span> Possible type of luminous blue compact galaxy

A Pea galaxy, also referred to as a Pea or Green Pea, might be a type of luminous blue compact galaxy that is undergoing very high rates of star formation. Pea galaxies are so-named because of their small size and greenish appearance in the images taken by the Sloan Digital Sky Survey (SDSS).

Boötes III is an overdensity in the Milky Way's halo, which may be a disrupted dwarf spheroidal galaxy. It is situated in the constellation Boötes and was discovered in 2009 in the data obtained by Sloan Digital Sky Survey. The galaxy is located at the distance of about 46 kpc from the Sun and moves away from it at the speed of about 200 km/s. It has an elongated shape with the radius of about 0.5 kpc. The large size and an irregular shape may indicate that Boötes III in a transitional phase between a gravitationally bound galaxy and completely unbound system.

<span class="mw-page-title-main">Intergalactic star</span> Star not gravitationally bound to any galaxy

An intergalactic star, also known as an intracluster star or a rogue star, is a star not gravitationally bound to any galaxy. Although a source of much discussion in the scientific community during the late 1990s, intergalactic stars are now generally thought to have originated in galaxies, like other stars, before being expelled as the result of either galaxies colliding or of a multiple-star system traveling too close to a supermassive black hole, which are found at the center of many galaxies.

<span class="mw-page-title-main">IC 3418</span> Galaxy in the constellation of Virgo

IC 3418 is a galaxy in the constellation Virgo. It is most well noted for its tidal tail, which formed after the galaxy collided with the Virgo Cluster some 54 million light years from Earth. The galaxy is home to many starburst regions.

<span class="mw-page-title-main">Anemic galaxy</span> Type of spiral galaxy characterized by a low contrast between its spiral arms and the disk

An anemic galaxy is a type of spiral galaxy characterized by a low contrast between its spiral arms and its disk.

SDSS J1229+1122 is a blue supergiant O-type star in the tail of dwarf irregular galaxy IC 3418. It illuminates a nebula clump of gas, and was discovered from the spectrum of the illumination source. The clump of gas resides in a tail caused by ram pressure stripping of gas from the galaxy by the galaxy cluster. It was determined to be a blue supergiant through analysis of its spectrum taken with the 8m Subaru telescope. The discovery was made by Youichi Ohyama and Ananda Hota, using the Subaru Telescope. This discovery was then followed up with the AstroSat to image it with finer angular resolution in the ultraviolet than that of GALEX. With addition of HST optical data the astronomers believe that the ram pressure stripped tail of IC3418 many have many such young star forming clumps and potentially single O-type stars.

<span class="mw-page-title-main">NGC 4457</span> Galaxy in the constellation of Virgo

NGC 4457 is an intermediate spiral galaxy located about 55 million light-years away in the constellation of Virgo. It is also classified as a LINER galaxy, a class of active galaxy defined by their spectral line emissions. NGC 4457 Is inclined by about 33°. It was discovered by astronomer William Herschel on February 23, 1784. Despite being listed in the Virgo Cluster Catalog as VCC 1145, NGC 4457 is a member of the Virgo II Groups which form an extension of the Virgo cluster.

<span class="mw-page-title-main">NGC 4522</span> Spiral galaxy in the constellation of Virgo

NGC 4522 is an edge-on spiral galaxy located about 60 million light-years away within the Virgo Cluster in the constellation Virgo. NGC 4522 is losing its molecular gas though ram-pressure stripping as it plows though the cluster at a speed of more than 10 million kilometres per hour. The galaxy was discovered by astronomer John Herschel on January 18, 1828.

<span class="mw-page-title-main">NGC 3859</span> Spiral galaxy in the constellation Leo

NGC 3859 is a spiral galaxy located about 295 million light-years away in the constellation Leo. It was discovered by astronomer Édouard Stephan on March 23, 1884. The galaxy is a member of the Leo Cluster.

<span class="mw-page-title-main">NGC 4324</span> Galaxy in the constellation of Virgo

NGC 4324 is a lenticular galaxy located about 85 million light-years away in the constellation Virgo. It was discovered by astronomer Heinrich d'Arrest on March 4, 1862. NGC 4324 has a stellar mass of 5.62 × 1010M☉, and a baryonic mass of 5.88 × 1010M☉. The galaxy's total mass is around 5.25 × 1011M☉. NGC 4324 is notable for having a ring of star formation surrounding its nucleus. It was considered a member of the Virgo II Groups until 1999, when its distance was recalculated and it was placed in the Virgo W Group.

References

  1. 1 2 3 4 5 Jones, Michael G.; Sand, David J.; Bellazzini, Michele; Spekkens, Kristine; Karunakaran, Ananthan; Adams, Elizabeth A. K.; Battaglia, Giuseppina; Beccari, Giacomo; Bennet, Paul; Cannon, John M.; Cresci, Giovanni; Crnojević, Denija; Caldwell, Nelson; Fuson, Jackson; Guhathakurta, Puragra (2022-08-01). "Young, Blue, and Isolated Stellar Systems in the Virgo Cluster. II. A New Class of Stellar System". The Astrophysical Journal. 935: 51. Bibcode:2022ApJ...935...51J. doi: 10.3847/1538-4357/ac7c6c . hdl: 10261/283719 . ISSN   0004-637X.
  2. ↑ Adams, E. A. K.; Cannon, J. M.; Rhode, K. L.; Janesh, W. F.; Janowiecki, S.; Leisman, L.; Giovanelli, R.; Haynes, M. P.; Oosterloo, T. A.; Salzer, J. J.; Zaidi, T. (2015-08-01). "AGC 226067: A possible interacting low-mass system". Astronomy and Astrophysics. 580: A134. arXiv: 1507.01855 . Bibcode:2015A&A...580A.134A. doi: 10.1051/0004-6361/201526857 . ISSN   0004-6361.
  3. ↑ Beccari, G.; Bellazzini, M.; Magrini, L.; Coccato, L.; Cresci, G.; Fraternali, F.; de Zeeuw, P. T.; Husemann, B.; Ibata, R.; Battaglia, G.; Martin, N.; Testa, V.; Perina, S.; Correnti, M. (2017-02-01). "A very dark stellar system lost in Virgo: kinematics and metallicity of SECCO 1 with MUSE". Monthly Notices of the Royal Astronomical Society. 465 (2): 2189–2197. arXiv: 1611.02876 . Bibcode:2017MNRAS.465.2189B. doi: 10.1093/mnras/stw2874 . ISSN   0035-8711.
  4. ↑ "Zooniverse". www.zooniverse.org. Retrieved 2023-09-25.
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.