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Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect, or emit electromagnetic radiation and is, therefore, difficult to detect. Various astrophysical observations – including gravitational effects which cannot be explained by currently accepted theories of gravity unless more matter is present than can be seen – imply dark matter's presence. For this reason, most experts think that dark matter is abundant in the universe and has had a strong influence on its structure and evolution.
A massive astrophysical compact halo object (MACHO) is a kind of astronomical body that might explain the apparent presence of dark matter in galaxy halos. A MACHO is a body that emits little or no radiation and drifts through interstellar space unassociated with any planetary system. Since MACHOs are not luminous, they are hard to detect. MACHO candidates include black holes or neutron stars as well as brown dwarfs and unassociated planets. White dwarfs and very faint red dwarfs have also been proposed as candidate MACHOs. The term was coined by astrophysicist Kim Griest.
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and 28, 1995.
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 and was named after the Alfred P. Sloan Foundation, which contributed significant funding.
The ΛCDM or Lambda-CDM model is a parameterization of the Big Bang cosmological model in which the universe contains three major components: first, a cosmological constant denoted by Lambda associated with dark energy; second, the postulated cold dark matter ; and third, ordinary matter. It is frequently referred to as the standard modelof Big Bang cosmology because it is the simplest model that provides a reasonably good account of the following properties of the cosmos:
In astronomy, a redshift survey is a survey of a section of the sky to measure the redshift of astronomical objects: usually galaxies, but sometimes other objects such as galaxy clusters or quasars. Using Hubble's law, the redshift can be used to estimate the distance of an object from Earth. By combining redshift with angular position data, a redshift survey maps the 3D distribution of matter within a field of the sky. These observations are used to measure detailed statistical properties of the large-scale structure of the universe. In conjunction with observations of early structure in the cosmic microwave background, these results can place strong constraints on cosmological parameters such as the average matter density and the Hubble constant.
In astronomy, the 2dF Galaxy Redshift Survey, 2dF or 2dFGRS is a redshift survey conducted by the Australian Astronomical Observatory (AAO) with the 3.9m Anglo-Australian Telescope between 1997 and 11 April 2002. The data from this survey were made public on 30 June 2003. The survey determined the large-scale structure in two large slices of the Universe to a depth of around 2.5 billion light years. It was the world's largest redshift survey between 1998 and 2003. Matthew Colless, Richard Ellis, Steve Maddox and John Peacock were in charge of the project. Team members Shaun Cole and John Peacock were awarded a share of the 2014 Shaw Prize in astronomy for results from the 2dFGRS.
In physical cosmology, structure formation is the formation of galaxies, galaxy clusters and larger structures from small early density fluctuations. The universe, as is now known from observations of the cosmic microwave background radiation, began in a hot, dense, nearly uniform state approximately 13.8 billion years ago. However, looking at the night sky today, structures on all scales can be seen, from stars and planets to galaxies. On even larger scales, galaxy clusters and sheet-like structures of galaxies are separated by enormous voids containing few galaxies. Structure formation attempts to model how these structures were formed by gravitational instability of small early ripples in spacetime density or another emergence.
The Cosmic Origins Spectrograph (COS) is a science instrument that was installed on the Hubble Space Telescope during Servicing Mission 4 (STS-125) in May 2009. It is designed for ultraviolet (90–320 nm) spectroscopy of faint point sources with a resolving power of ≈1,550–24,000. Science goals include the study of the origins of large scale structure in the universe, the formation and evolution of galaxies, and the origin of stellar and planetary systems and the cold interstellar medium. COS was developed and built by the Center for Astrophysics and Space Astronomy (CASA-ARL) at the University of Colorado at Boulder and the Ball Aerospace and Technologies Corporation in Boulder, Colorado.
The warm–hot intergalactic medium (WHIM) is the sparse, warm-to-hot (105 to 107 K) plasma that cosmologists believe to exist in the spaces between galaxies and to contain 40–50% of the baryonic 'normal matter' in the universe at the current epoch. The WHIM can be described as a web of hot, diffuse gas stretching between galaxies, and consists of plasma, as well as atoms and molecules, in contrast to dark matter. The WHIM is a proposed solution to the missing baryon problem, where the observed amount of baryonic matter does not match theoretical predictions from cosmology.
In cosmology, baryon acoustic oscillations (BAO) are fluctuations in the density of the visible baryonic matter of the universe, caused by acoustic density waves in the primordial plasma of the early universe. In the same way that supernovae provide a "standard candle" for astronomical observations, BAO matter clustering provides a "standard ruler" for length scale in cosmology. The length of this standard ruler is given by the maximum distance the acoustic waves could travel in the primordial plasma before the plasma cooled to the point where it became neutral atoms, which stopped the expansion of the plasma density waves, "freezing" them into place. The length of this standard ruler can be measured by looking at the large scale structure of matter using astronomical surveys. BAO measurements help cosmologists understand more about the nature of dark energy by constraining cosmological parameters.
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).
The Galaxy And Mass Assembly (GAMA) survey is a project to exploit the latest generation of ground-based wide-field survey facilities to study cosmology and galaxy formation and evolution. GAMA will bring together data from a number of world class instruments:
Alice Eve Shapley is a professor at the University of California, Los Angeles (UCLA) in the Department of Physics and Astronomy. She was one of the discoverers of the spiral galaxy BX442. Through her time at University of California, Los Angeles (UCLA) she has taught Nature of the Universe, Black Holes and Cosmic Catastrophes, Cosmology: Our Changing Concepts of the Universe, Galaxies, Scientific Writing, AGNs, Galaxies, *and* Writing, and The Formation and Evolution of Galaxies and the IGM. Shapley has committed herself too over a two decades of research and publication in the interest of physics and astronomy.
Christy A. Tremonti is an observational astronomer on the faculty at the University of Wisconsin–Madison. She was a 2005 Hubble Fellow while at the University of Arizona. She received her PhD from Johns Hopkins University in 2003 and her BS from Colgate University in 1994. She completed her dissertation, "The physical properties of low redshift star forming galaxies: Insights from the space-UV and 20,000 SDSS spectra", under the supervision of Timothy M. Heckman.
The WiggleZ Dark Energy Survey was a large-scale astronomical redshift survey carried out on the 3.9 metre Anglo-Australian Telescope (AAT) at the Siding Spring Observatory, New South Wales between August 2006 and January 2011. The name stems from the measurement of baryon acoustic oscillations in the distribution of galaxies.
In cosmology, the missing baryon problem is an observed discrepancy between the amount of baryonic matter detected from shortly after the Big Bang and from more recent epochs. Observations of the cosmic microwave background and Big Bang nucleosynthesis studies have set constraints on the abundance of baryons in the early universe, finding that baryonic matter accounts for approximately 4.8% of the energy contents of the Universe. At the same time, a census of baryons in the recent observable universe has found that observed baryonic matter accounts for less than half of that amount. This discrepancy is commonly known as the missing baryon problem. The missing baryon problem is different from the dark matter problem, which is non-baryonic in nature.
Juna Kollmeier is an astrophysicist from the US. She is currently employed at the Carnegie Institution for Science and is the director of the fifth phase of the Sloan Digital Sky Survey, which made its first observations in October, 2020. She has been named Director of the Canadian Institute for Theoretical Astrophysics, located at the University of Toronto, and will take up this position in July, 2021.
Erika Tobiason Hamden is an American astrophysicist and Assistant Professor at the University of Arizona and Steward Observatory. Her research focuses on developing ultraviolet (UV) detector technology, ultraviolet–visible spectroscopy (UV/VIS) instrumentation and spectroscopy, and galaxy evolution. She served as the project scientist and project manager of a UV multi-object spectrograph, FIREBall-2, that is designed to observe the circumgalactic medium (CGM). She is a 2019 TED fellow.
Hsiao-Wen Chen is a Taiwanese-American astronomer who uses absorption spectroscopy to study baryonic "normal matter" in the intergalactic medium and galactic halos, and the connections between this matter and the matter in star-forming regions of galaxies. She is a professor of astronomy and astrophysics at the University of Chicago.
References
- 1 2 3 "UW Department Faculty Spotlight: Jessica Werk". depts.washington.edu. Archived from the original on 2017-04-01. Retrieved 2017-04-11.
- ↑ "Hubble Fellowships Listing of All Hubble Fellows 1990-2017". Archived from the original on 2013-04-09. Retrieved 2017-04-12.
- ↑ "Prof. Jessica Werk Awarded Sloan Fellowship – Department of Astronomy". Archived from the original on 2019-05-11. Retrieved 2019-05-11.
- ↑ Beck, Dr Kenneth (2018-02-18). "UW Astronomy Prof Dr Jessica K Werk receives prestigious Sloan Award". i really appreciate science. Archived from the original on 2019-05-11. Retrieved 2019-05-11.
- 1 2 "Werk, Jessica - Department of Astronomy". Archived from the original on 2017-03-31. Retrieved 2017-04-12.
- ↑ "Home - NSF Graduate Research Fellowships Program (GRFP)". www.nsfgrfp.org. Archived from the original on 2017-05-09. Retrieved 2017-05-10.
- ↑ "Jessica Werk LinkedIn Profile".
- ↑ "The COS-Halos Survey". www.stsci.edu. Retrieved 2017-05-10.
- ↑ Werk, Jessica K.; Prochaska, J. Xavier; Thom, Christopher; et al. (February 2013). "The COS-Halos Survey: An Empirical Description of Metal-line Absorption in the Low-redshift Circumgalactic Medium". Astrophysical Journal Supplement. 204 (2). 17. arXiv: 1212.0558 . Bibcode:2013ApJS..204...17W. doi: 10.1088/0067-0049/204/2/17 .
- ↑ Werk, Jessica K.; Prochaska, J. Xavier; Tumlinson, Jason; et al. (September 2014). "The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-redshift Circumgalactic Medium". Astrophysical Journal. 792 (1). 8. arXiv: 1403.0947 . Bibcode:2014ApJ...792....8W. doi: 10.1088/0004-637X/792/1/8 .
