Is there a Supermassive Black Hole at the Center of the Milky Way?
... density is 4 × 109 M⊙ pc−3 . Were one to place 4 × 107 stars inside a radius of 0.13 parsecs, the system would be dynamically unstable with less massive stars being expelled (“evaporated”) and more massive stars sinking to the center, colliding and possibly forming a black hole. The timescale for th ...
... density is 4 × 109 M⊙ pc−3 . Were one to place 4 × 107 stars inside a radius of 0.13 parsecs, the system would be dynamically unstable with less massive stars being expelled (“evaporated”) and more massive stars sinking to the center, colliding and possibly forming a black hole. The timescale for th ...
Dark Matter, Dark Energy, and the Fate of the Universe
... In principle, we could determine the complete distribution of mass in the Milky Way by doing the same thing with the orbits of stars at every different distance from the galactic center. In practice, interstellar dust obscures our view of disk stars more than a few thousand light-years away from us, ...
... In principle, we could determine the complete distribution of mass in the Milky Way by doing the same thing with the orbits of stars at every different distance from the galactic center. In practice, interstellar dust obscures our view of disk stars more than a few thousand light-years away from us, ...
Teaching Tips Table of Contents - Hubble Deep Field
... Activity description ........................................................................................................... 1 Grade levels / Target audience........................................................................................ 1 Subjects ....................................... ...
... Activity description ........................................................................................................... 1 Grade levels / Target audience........................................................................................ 1 Subjects ....................................... ...
SUB-KILOPARSEC IMAGING OF COOL MOLECULAR GAS IN
... Carbon monoxide (12 C16 O; hereafter CO) has long been known as a tracer of molecular hydrogen gas in galaxies. Molecular gas is the fuel for new generations of stars (for recent reviews, see Bolatto et al. 2013 and Carilli & Walter 2013), so accurately diagnosing its abundance, kinematics, and morp ...
... Carbon monoxide (12 C16 O; hereafter CO) has long been known as a tracer of molecular hydrogen gas in galaxies. Molecular gas is the fuel for new generations of stars (for recent reviews, see Bolatto et al. 2013 and Carilli & Walter 2013), so accurately diagnosing its abundance, kinematics, and morp ...
Star formation in a galactic outflow
... the ratio between ionizing photon flux and gas density; when divided by the speed of light it is the adimensional ionization parameter U) much lower than typically observed in star-forming galaxies. Yet, despite the gas density in the outflow (~600-1,500 cm-3, as inferred from the [SII] doublet) bei ...
... the ratio between ionizing photon flux and gas density; when divided by the speed of light it is the adimensional ionization parameter U) much lower than typically observed in star-forming galaxies. Yet, despite the gas density in the outflow (~600-1,500 cm-3, as inferred from the [SII] doublet) bei ...
Confirmation of Hostless Type Ia Supernovae Using Hubble Space
... above results are based on αd = −1.0, which is true for field galaxies (Blanton et al. 2003), but αd may be higher in rich galaxy clusters (e.g., Milne et al. 2007). Adopting αd = −1.5 as an upper limit, the MENeaCS survey estimated that . 2% of the stellar mass in dwarf cluster galaxies below dete ...
... above results are based on αd = −1.0, which is true for field galaxies (Blanton et al. 2003), but αd may be higher in rich galaxy clusters (e.g., Milne et al. 2007). Adopting αd = −1.5 as an upper limit, the MENeaCS survey estimated that . 2% of the stellar mass in dwarf cluster galaxies below dete ...
The old globular cluster system of the dIrr galaxy NGC 1427A in the
... (Z < 0.4 × Z⊙ ) population as judged by simple stellar population models. Our contamination analysis indicates that the density distribution of GCs in the outskirts of the Fornax central cD galaxy NGC 1399 may not be spherically symmetric. We derive a present-day specific frequency SN of 1.6 for NGC ...
... (Z < 0.4 × Z⊙ ) population as judged by simple stellar population models. Our contamination analysis indicates that the density distribution of GCs in the outskirts of the Fornax central cD galaxy NGC 1399 may not be spherically symmetric. We derive a present-day specific frequency SN of 1.6 for NGC ...
Article PDF - IOPscience
... irregular galaxy (SagDIG), which now places this object very close to the edge of the Local Group zerovelocity surface ; (3) more information on the evolutionary histories of some individual Local Group members ; and (4) improved distance determinations to, and luminosities for, a number of Local Gr ...
... irregular galaxy (SagDIG), which now places this object very close to the edge of the Local Group zerovelocity surface ; (3) more information on the evolutionary histories of some individual Local Group members ; and (4) improved distance determinations to, and luminosities for, a number of Local Gr ...
Superbubble Activity in Star-Forming Galaxies M. S. Oey
... cooler shells should generate intermediate temperatures and ions. Chu et al. (1994) searched a number sightlines through LMC superbubbles and confirmed the existence of C iv and Si iv absorption in all cases. A stringent test of the adiabatic model is to compare the predicted and observed shell kine ...
... cooler shells should generate intermediate temperatures and ions. Chu et al. (1994) searched a number sightlines through LMC superbubbles and confirmed the existence of C iv and Si iv absorption in all cases. A stringent test of the adiabatic model is to compare the predicted and observed shell kine ...
A catalogue of the Chandra Deep Field South with multi
... All procedures used for the data reduction are based on the MIDAS package. A WFI image processing pipeline was developed by Wolf et al. (2001) and makes intensive use of programmes developed by K. Meisenheimer, H.-J. Röser and H. Hippelein for the Calar Alto Deep Imaging Survey (CADIS). The pipelin ...
... All procedures used for the data reduction are based on the MIDAS package. A WFI image processing pipeline was developed by Wolf et al. (2001) and makes intensive use of programmes developed by K. Meisenheimer, H.-J. Röser and H. Hippelein for the Calar Alto Deep Imaging Survey (CADIS). The pipelin ...
ALMA Science Results
... Most of star formation occurs in very compact (few pc) massive (>10^5 Msun) super star clusters. What triggers their formation? – Cycle 2 data could not see SiO but did get 13CO 2-1. Combine with H2 emission data from VLT. H2 kinematics like CO. – What power H2? Line ratios suggest shocks do the exc ...
... Most of star formation occurs in very compact (few pc) massive (>10^5 Msun) super star clusters. What triggers their formation? – Cycle 2 data could not see SiO but did get 13CO 2-1. Combine with H2 emission data from VLT. H2 kinematics like CO. – What power H2? Line ratios suggest shocks do the exc ...
Chapter 14 Black Holes as Central Engines
... • The redshift of 3C273 corresponds to a recessional velocity about 15 percent of the speed of light, if interpreted as a Doppler shift (later we shall see that such cosmological redshifts should not be interpreted as Doppler shifts, though). • Once this was realized for 3C273, it quickly became app ...
... • The redshift of 3C273 corresponds to a recessional velocity about 15 percent of the speed of light, if interpreted as a Doppler shift (later we shall see that such cosmological redshifts should not be interpreted as Doppler shifts, though). • Once this was realized for 3C273, it quickly became app ...
Galaxy Spiral Arms
... This is actually the same Gravitation that Newton had quantified, but it is an entirely different perspective. Think of any galaxy spiral arm as a very large and massive “open cluster” of stars. We all accept that open clusters have a structural integrity due to mutual gravitation, even while revolv ...
... This is actually the same Gravitation that Newton had quantified, but it is an entirely different perspective. Think of any galaxy spiral arm as a very large and massive “open cluster” of stars. We all accept that open clusters have a structural integrity due to mutual gravitation, even while revolv ...
Simulations of the galaxy population constrained by observations
... formation is needed, for example, for analysis of galaxy clustering, it is more effective to extract them directly from numerical simulations (Roukema et al. 1997; Kauffmann et al. 1999; Helly et al. 2003; Hatton et al. 2003). With increasing numerical resolution it becomes possible to base the tree ...
... formation is needed, for example, for analysis of galaxy clustering, it is more effective to extract them directly from numerical simulations (Roukema et al. 1997; Kauffmann et al. 1999; Helly et al. 2003; Hatton et al. 2003). With increasing numerical resolution it becomes possible to base the tree ...
Gamma Ray Burst Afterglows and Host Galaxies
... radio sources to “twinkle” (like stars seen in visible light through our atmosphere). • Larger sources do not twinkle (like planets). • Measuring the time when an afterglow stops “twinkling” at radio wavelengths reveals its speed of expansion to be near light speed. ...
... radio sources to “twinkle” (like stars seen in visible light through our atmosphere). • Larger sources do not twinkle (like planets). • Measuring the time when an afterglow stops “twinkling” at radio wavelengths reveals its speed of expansion to be near light speed. ...
sections 19-22 instructor notes
... have obtained values for A ranging from 11.6 km/s/kpc to 20.0 km/s/kpc, and values for B ranging from –7.0 km/s/kpc to –18 km/s/kpc. A proper motion study from the Lick Northern Proper Motion Program (Hanson AJ, 94, 409, 1987) yielded estimates of A = +11.31 ±1.06 km/s/kpc and B = –13.91 ±0.92 km/s/ ...
... have obtained values for A ranging from 11.6 km/s/kpc to 20.0 km/s/kpc, and values for B ranging from –7.0 km/s/kpc to –18 km/s/kpc. A proper motion study from the Lick Northern Proper Motion Program (Hanson AJ, 94, 409, 1987) yielded estimates of A = +11.31 ±1.06 km/s/kpc and B = –13.91 ±0.92 km/s/ ...
sections 19-22 instructor notes
... have obtained values for A ranging from 11.6 km/s/kpc to 20.0 km/s/kpc, and values for B ranging from –7.0 km/s/kpc to –18 km/s/kpc. A proper motion study from the Lick Northern Proper Motion Program (Hanson AJ, 94, 409, 1987) yielded estimates of A = +11.31 ±1.06 km/s/kpc and B = –13.91 ±0.92 km/s/ ...
... have obtained values for A ranging from 11.6 km/s/kpc to 20.0 km/s/kpc, and values for B ranging from –7.0 km/s/kpc to –18 km/s/kpc. A proper motion study from the Lick Northern Proper Motion Program (Hanson AJ, 94, 409, 1987) yielded estimates of A = +11.31 ±1.06 km/s/kpc and B = –13.91 ±0.92 km/s/ ...
– 1 – 1. Emission Lines in Nearby Galaxies 1.1.
... electron temperature. The strength of forbidden lines is easy to calculate since they are almost always optically thin in HII regions and the density is low, so collisional de-excitation can be ignored. This results in an overpopulation of the metastable states and the forbidden transitions dominate ...
... electron temperature. The strength of forbidden lines is easy to calculate since they are almost always optically thin in HII regions and the density is low, so collisional de-excitation can be ignored. This results in an overpopulation of the metastable states and the forbidden transitions dominate ...
astronomy (astr)
... education (EE) credit. Observing with radio telescopes and antennae: supernova remnants, star-forming regions, normal and active galaxies, quasars, solar system objects (sun, moon, Jupiter), radio spectroscopy. Gen Ed: EE-Field Work. Grading status: Letter grade. ASTR 205. The Medieval Foundations o ...
... education (EE) credit. Observing with radio telescopes and antennae: supernova remnants, star-forming regions, normal and active galaxies, quasars, solar system objects (sun, moon, Jupiter), radio spectroscopy. Gen Ed: EE-Field Work. Grading status: Letter grade. ASTR 205. The Medieval Foundations o ...
The ATLAS3D project-XXII. Low-efficiency star formation in early
... simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the earlytype galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars two to five times less efficiently ...
... simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the earlytype galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars two to five times less efficiently ...
The Milky Way disk
... Abstract / This review summarises the invited presentation I gave on the Milky Way disc. The idea underneath was to touch those topics that can be considered hot nowadays in the Galactic disk research: the reality of the thick disk, the spiral structure of the Milky Way, and the properties of the ou ...
... Abstract / This review summarises the invited presentation I gave on the Milky Way disc. The idea underneath was to touch those topics that can be considered hot nowadays in the Galactic disk research: the reality of the thick disk, the spiral structure of the Milky Way, and the properties of the ou ...
P1 09 Red Shift - Animated Science
... (a) A student listens to the sound waves produced by a car siren. When the car is stationary, the student hears a constant frequency sound. Describe how the wavelength and frequency of the sound waves heard by the student change when the car is driven away from the student. ...
... (a) A student listens to the sound waves produced by a car siren. When the car is stationary, the student hears a constant frequency sound. Describe how the wavelength and frequency of the sound waves heard by the student change when the car is driven away from the student. ...
The Interstellar Medium White Paper
... From a theoretical perspective, although the picture is becoming steadily clearer, there are many aspects of the dynamics of the Galactic nucleus and its outflow that we do not understand. It is still under debate, for instance, whether it has indeed been star formation (Crocker and Aharonian 2011) ...
... From a theoretical perspective, although the picture is becoming steadily clearer, there are many aspects of the dynamics of the Galactic nucleus and its outflow that we do not understand. It is still under debate, for instance, whether it has indeed been star formation (Crocker and Aharonian 2011) ...
The cosmological significance of high
... (1971). Wakker & van Woerden (1991) noted that this HVC seems to be associated in position and velocity with a large number of other clouds, and named the grouping Complex H after Hulsbosch. The complex subtends 478 deg2 (Wakker & van Woerden 1991) and extends in velocity all the way from VLSR = −23 ...
... (1971). Wakker & van Woerden (1991) noted that this HVC seems to be associated in position and velocity with a large number of other clouds, and named the grouping Complex H after Hulsbosch. The complex subtends 478 deg2 (Wakker & van Woerden 1991) and extends in velocity all the way from VLSR = −23 ...
Collisions and Encounters of Stellar Systems
... galaxy are contained within a radius R ≈ 10 kpc, so the collision cross-section between two such galaxies is Σ ≈ π(2R)2 . If the positions and velocities of the galaxies are uncorrelated, the rate at which an L! galaxy suffers collisions with similar galaxies is then expected to be of order nΣvp ≈ 1 ...
... galaxy are contained within a radius R ≈ 10 kpc, so the collision cross-section between two such galaxies is Σ ≈ π(2R)2 . If the positions and velocities of the galaxies are uncorrelated, the rate at which an L! galaxy suffers collisions with similar galaxies is then expected to be of order nΣvp ≈ 1 ...
Galaxy
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas and dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally ""milky"", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few thousand (103) stars to giants with one hundred trillion (1014) stars, each orbiting their galaxy's own center of mass. Galaxies are categorized according to their visual morphology, including elliptical, spiral, and irregular. Many galaxies are thought to have black holes at their active centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than our own Sun. As of July 2015, EGSY8p7 is the oldest and most distant galaxy with a light travel distance of 13.2 billion light-years from Earth, and observed as it existed 570 million years after the Big Bang. Previously, as of May 2015, EGS-zs8-1 was the most distant known galaxy, estimated to have a light travel distance of 13.1 billion light-years away and to have 15% of the mass of the Milky Way.Approximately 170 billion (1.7 × 1011) to 200 billion (2.0 × 1011) galaxies exist in the observable universe. Most of the galaxies are 1,000 to 100,000 parsecs in diameter and usually separated by distances on the order of millions of parsecs (or megaparsecs). The space between galaxies is filled with a tenuous gas with an average density less than one atom per cubic meter. The majority of galaxies are gravitationally organized into associations known as galaxy groups, clusters, and superclusters. At the largest scale, these associations are generally arranged into sheets and filaments that are surrounded by immense voids.