Astrophysics Questions (DRAFT)
... 18. What is \brightness temperature"? What are typical brightness temperatures of (a) an H II region at 5 GHz; (b) a radio pulsar at 1 GHz; (c) a compact extragalactic radio source at 5 GHz; (d) the sun at 100 MHz; (e) a Citizen's Band radio? 19. Explain the steps you would take to show that both th ...
... 18. What is \brightness temperature"? What are typical brightness temperatures of (a) an H II region at 5 GHz; (b) a radio pulsar at 1 GHz; (c) a compact extragalactic radio source at 5 GHz; (d) the sun at 100 MHz; (e) a Citizen's Band radio? 19. Explain the steps you would take to show that both th ...
PPT
... • How are the lives of galaxies connected with the history of the universe? • What are the three major types of galaxies? • How are galaxies grouped together? Recall: The Sun is only one star among well over 100 billion stars in our own galaxy, the Milky Way, which has the form of a highly flattened ...
... • How are the lives of galaxies connected with the history of the universe? • What are the three major types of galaxies? • How are galaxies grouped together? Recall: The Sun is only one star among well over 100 billion stars in our own galaxy, the Milky Way, which has the form of a highly flattened ...
PPT - ALFALFA survey
... Schneider (2000). It was a drift-scan survey taken in a series of declination strips with the Arecibo 305-m telescope. The velocity limit of the ADBS is 8000 km/s (it is volume limited!). The full ADBS sample includes 265 galaxies over ~420 sq. deg. • Since it is a “blind” HI survey, it does not suf ...
... Schneider (2000). It was a drift-scan survey taken in a series of declination strips with the Arecibo 305-m telescope. The velocity limit of the ADBS is 8000 km/s (it is volume limited!). The full ADBS sample includes 265 galaxies over ~420 sq. deg. • Since it is a “blind” HI survey, it does not suf ...
Dark Matter— More Than Meets The Eye
... center of the galaxy than are the visible stars and gas. In fact, evidence shows that the average density of the nonluminous matter at large distances from the center may be as much as 1000 times greater than the mean density of the mass in the universe. So, dark matter may be clumped around galaxi ...
... center of the galaxy than are the visible stars and gas. In fact, evidence shows that the average density of the nonluminous matter at large distances from the center may be as much as 1000 times greater than the mean density of the mass in the universe. So, dark matter may be clumped around galaxi ...
Distance Determination of the Hubble Constant Ho by the
... • Ho is determined by comparing the recessional velocity of galaxies, determined from their redshift, and the distance to that galaxy. • Ho = v/d • The main difficulties lie in getting accurate distances to galaxies, since the velocities of galaxies can be accurately measured using Doppler measurmen ...
... • Ho is determined by comparing the recessional velocity of galaxies, determined from their redshift, and the distance to that galaxy. • Ho = v/d • The main difficulties lie in getting accurate distances to galaxies, since the velocities of galaxies can be accurately measured using Doppler measurmen ...
Disk Galaxies and problem 3
... This is observationally seen in grand-design spirals, such as M51. The tidal arms are also easily produced in numerical simulations, see Fig. 7. • Bar spiral arms. A rotating bar at the centre of galaxies can also induce spiral arms that can last for a long time. This may be another way to form gran ...
... This is observationally seen in grand-design spirals, such as M51. The tidal arms are also easily produced in numerical simulations, see Fig. 7. • Bar spiral arms. A rotating bar at the centre of galaxies can also induce spiral arms that can last for a long time. This may be another way to form gran ...
Dark Matter: Observational Constraints
... – Argued that virial theorem was the most accurate way to determine the mass of relaxed galaxy clusters (Coma). 2T + V = 0 – Argued that traditional methods of getting nebular (galaxy) was highly biased and inaccurate (photometry, rotation). – Showed that for Coma cluster, virial mass ~ 400 x mass i ...
... – Argued that virial theorem was the most accurate way to determine the mass of relaxed galaxy clusters (Coma). 2T + V = 0 – Argued that traditional methods of getting nebular (galaxy) was highly biased and inaccurate (photometry, rotation). – Showed that for Coma cluster, virial mass ~ 400 x mass i ...
Our galaxy - School of Physics
... • The story of how we found out the shape of the Galaxy is told in a lovely book, “Minding the Heavens: The Story of our Discovery of the Milky Way” by Leila Belkora (IoP, 2003). • The website of the UCLA Galactic Centre group is at http://www.galacticcenter.astro.ucla.edu/. It contains lots of inte ...
... • The story of how we found out the shape of the Galaxy is told in a lovely book, “Minding the Heavens: The Story of our Discovery of the Milky Way” by Leila Belkora (IoP, 2003). • The website of the UCLA Galactic Centre group is at http://www.galacticcenter.astro.ucla.edu/. It contains lots of inte ...
Molecular clouds
... • How is gas recycled in our galaxy? — Gas from dying stars mixes new elements into the interstellar medium which slowly cools, making the molecular clouds where stars form. — Those stars will eventually return much of their matter to interstellar space. ...
... • How is gas recycled in our galaxy? — Gas from dying stars mixes new elements into the interstellar medium which slowly cools, making the molecular clouds where stars form. — Those stars will eventually return much of their matter to interstellar space. ...
Galactic Thin Disk - Caltech Astronomy
... where h is called the scale length. The surface brightness L(R) is expressed here in L pc−2 , but in practice is measured in magnitudes per arcsec2 and indicated by µ. For the majority of the bright spiral galaxies, Freeman in 1970 found that the central surface brightness was remarkably constant a ...
... where h is called the scale length. The surface brightness L(R) is expressed here in L pc−2 , but in practice is measured in magnitudes per arcsec2 and indicated by µ. For the majority of the bright spiral galaxies, Freeman in 1970 found that the central surface brightness was remarkably constant a ...
Messier 87
Messier 87 (also known as Virgo A or NGC 4486, and generally abbreviated to M87) is a supergiant elliptical galaxy in the constellation Virgo. One of the most massive galaxies in the local universe, it is notable for its large population of globular clusters—M87 contains about 12,000 compared to the 150-200 orbiting the Milky Way—and its jet of energetic plasma that originates at the core and extends outward at least 1,500 parsecs (4,900 light-years), travelling at relativistic speed. It is one of the brightest radio sources in the sky, and is a popular target for both amateur astronomy observations and professional astronomy study.French astronomer Charles Messier discovered M87 in 1781, cataloguing it as a nebulous feature while searching for objects that would confuse comet hunters. The second brightest galaxy within the northern Virgo Cluster, M87 is located about 16.4 million parsecs (53.5 million light-years) from Earth. Unlike a disk-shaped spiral galaxy, M87 has no distinctive dust lanes. Instead, it has an almost featureless, ellipsoidal shape typical of most giant elliptical galaxies, diminishing in luminosity with distance from the centre. Forming around one sixth of M87's mass, the stars in this galaxy have a nearly spherically symmetric distribution, their density decreasing with increasing distance from the core. At the core is a supermassive black hole, which forms the primary component of an active galactic nucleus. This object is a strong source of multiwavelength radiation, particularly radio waves. M87's galactic envelope extends out to a radius of about 150 kiloparsecs (490,000 light-years), where it has been truncated—possibly by an encounter with another galaxy. Between the stars is a diffuse interstellar medium of gas that has been chemically enriched by elements emitted from evolved stars.