Astronomy and Astrophysics in the New Millennium Panel Reports (2001) / Chapter Skim
Currently Skimming:
2 Report of the Panel on Optical and Infrared Astronomy from the Ground
2 Report of the Panel on Optical and Infrared Astronomy from the Ground
Pages 65-122
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 65... ...
Optca~ an] Infrared Astronomy from the Ground Report of the Panel on
|
From page 66... ...
Establishing a common vision within the astronomy community of how these facilities should evolve is the foundation of the recommendations of the Panel on Optical and Infrared Astronomy from the Ground for the coming decade. In this context, the panel proposes three initiatives to encourage the evolution of U.S.
|
From page 67... ...
With diffraction-limited performance down to at least 1 ,um, an order-of-magnitude increase in light-gathering power, and a factor-of-4 gain in spatial resolution, GSMT will enable breakthrough science in studies of star and planet formation, stellar populations, and early galaxy evolution. The GSMT's spatial resolution of 14 milliarcsec at 2 ,um and its high spectral resolution in the near-infrared region will significantly exceed the performance of the Next Generation Space Telescope (NGST, scheduled for launch in 2008)
|
From page 68... ...
· Produce extremely deep images over hundreds of square degrees for studying the distribution of dark matter through weak gravitational tensing. More than just a telescope, LSST with WAVE will make important strides in data processing, data mining tools, and archiving components and will play a key role in the National Virtual Observatory (NVO)
|
From page 69... ...
CIENCE OPPORTUNIT ANSWERING FUNDAMENTAL QUESTIONS The world's astronomy community has built powerful tools with which to answer fundamental questions about the birth of galaxies, stars, and planets and to explore the most exotic phenomena in the universe. These tools include (1)
|
From page 70... ...
· Connect the formation of supermassive black holes to galaxy formation and evolution. Discover the epoch of black hole formation, the dynamics of the process, and the relation to star formation in the nuclei of galaxies.
|
From page 71... ...
The x-ray halos of galaxies and the hot interstellar gas in rich clusters are being understood thanks to both space-based observations and ground-based optical data, and the recent discovery that gamma-ray bursts take place in distant galaxies, making them the most energetic known phenomenon, is the result of hard-won spectroscopic data from the Beck telescopes and rapid-response imaging from a variety of ground-based instruments. The ambitious scientific program outlined above requires a broad suite of telescopes with a range of aperture sizes and powerful state-ofthe-art instrumentation employing the latest array detectors.
|
From page 72... ...
ground-based O/IR system, NOAO must have as its first priority to represent the entire U.S. astronomy community, carrying on activities that benefit all.
|
From page 73... ...
The GSMT will be a filled-aperture, diffraction-limited telescope with atmospheric correction by AO down to at least 1 ,um. It will achieve order-of-magnitude gains over any extant ground-based O/IR telescope and will provide substantial gains in spatial resolution and nearIR high-resolution spectroscopy even over NGST, for which it will be an essential complement (Figure 2.11.
|
From page 74... ...
Its high spatial resolution and powerful spectroscopic capability will be a true quantum leap over any other existing or planned U.S. facility.
|
From page 75... ...
Despite its key role in processes as diverse as the origin of planetary systems and the evolution of galaxies, star formation is probably the leastunderstood aspect of the fundamental processes. Nonetheless, over the last quarter of the 20th century impressive advances in our understanding of star formation came from the continued development of new technological observational capabilities from both the ground and space.
|
From page 76... ...
Existing theories cannot simultaneously account for all these facts, and there are additional mysteries for example, the form of the initial mass function (IMF) and the efficiency of star formation both need to be understood in order to construct a credible theory of star formation.
|
From page 77... ...
Such observations will critically constrain the theory of stellar evolution through direct measurements of 77 FIGURE 2.2 Direct images ofthe debris disk around the main sequence A star HR 4796 show the advantage of high spatial resolution and the interplay between ground- and space-based facilities. On the left is a mid-lR image (24.5 Em)
|
From page 78... ...
High-angular-resolution imaging and spectroscopy will permit measurement of the frequency, separations, and orbital motions of binary companions to protostars and more evolved young stellar objects, such as T Tauri stars, on scales of 1 to 5 AU in the nearest star-forming regions. Such measurements would yield the first direct determinations of protostellar masses, crucial to the development of a complete theory of star formation, and indicate the survivability of protoplanetary disks in multiple-star systems.
|
From page 79... ...
Keck Observatory Adaptive Optics Team. within 2 to 4 pc of Earth.
|
From page 80... ...
as a function of look-back time. However, to place these objects in a meaningful cosmological context will require much more demanding physical measurements of smallspatial-scale internal kinematics, chemical abundances and gradients, gas-phase physical conditions, stellar content, and subkiloparsec morphology.
|
From page 81... ...
NGST and 8- to 10m telescopes will provide follow-up spectroscopy for measuring redshift and determining star formation rates. The GSMT will provide unique access to the chemical and dynamical history ofthe I < z < 5 universe through its powerful spectroscopic and imaging capabilities.
|
From page 82... ...
What controls the decline in the global star formation rate for z < 1? What is the mass function (as opposed to the luminosity function)
|
From page 83... ...
The core ofthe galaxy is barely resolved at 1.6 ,um with the HST. Higher spatial resolution, such as that of a diffraction-limited GSMT, will be required to resolve such galaxies into individual star-forming knots and to delve into the detailed kinematics that will allow measurements of, for example, dynamical mass, chemical abundance gradients, and the distribution of outflowing metal-enriched gas.
|
From page 84... ...
1 arcsec2. The GSMT will sample such an object with seven times the spatial resolution, corresponding to ~ 100 pc, the size of a large starforming region at high redshift.
|
From page 85... ...
An analysis ofthis spectrum indicates chemical abundances slightly less than solar and a galactic-scale outflow of gas at a velocity of more than 200 km so. The GSMT will obtain such measurements routinely for common, unlensed galaxies.
|
From page 86... ...
THE STAR FORMATjON H j STORY OF N EARLY GA~AX jES Did star formation begin in all galaxies at the same time, and did it proceed from the outside in or inside out? Was it episodic or continuous, and does this depend on galaxy mass or environment?
|
From page 87... ...
For example, · Densely sampled, wide-field spectroscopic surveys with GSMT will explore the evolution of large-scale structure beyond the local universe mapped by the Sloan Digital Sky Survey, i.e., at z > 1, allowing astronomers to distinguish among theories of structure formation. At z ~ 1, the 20 arcmin FOV of GSMT corresponds to a co-moving length scale of ~ 12 h-iMpc (q0 = 0.1)
|
From page 88... ...
To sort out these story lines and the complex relationships between them, it is necessary to trace out galaxy age, star-formation rate, chemical abundance, and morphology as functions of mass and environment over the large redshift range 1 < z < 5. Considering this large parameter space, the relative rarity of populating some bins (for example, very metal-poor starbursts)
|
From page 89... ...
This capability has greatly reduced the risk inherent in designing and building larger telescopes. Adaptive optics, a key component of a future very-large-aperture telescope, progressed significantly in the 1990s.
|
From page 90... ...
; · Better understanding of multiconjugate adaptive optics through modeling, simulations, and experiments; · Advanced techniques and algorithms for achieving the needed computing speed; · Study of various hybrid systems using both natural and laser guide stars; and · New, more efficient wavefront sensing approaches (ideas, simulations, and experiments)
|
From page 91... ...
In scaling up from 4-m-class telescopes, Gemini and Keck broke the cost curve by factors of 4 to 8. Clearly, then, the astronomy community has experience and success with this kind of challenge.
|
From page 92... ...
For example, segment size is a key cost driver: gravity-driven deflections of mirror segments are a major difficulty, one that increases as the fourth power of the radius of the segment. Smaller segments will therefore allow much thinner segments as well as simpler passive supports.
|
From page 93... ...
For all of the alternatives, the observing time available to the U.S. astronomy community, an amount proportional to the investment by NSF, could be distributed by NOAO (as is being done for the WIYN telescope)
|
From page 94... ...
Experience with the GSMT and NGST technologies will help to determine whether even larger ground-based telescopes, for example, the proposed 100-m OWL telescope, will be more cost-effective than space telescopes. ANCILLARY BENEFITS A 30-m telescope with its superb angular resolution and sensitivity may be the preferred way to follow up extremely faint sources associated with x-ray, gamma-ray, and microjansky radio sources, particularly if more than merely a redshift is desired.
|
From page 95... ...
, whereby one or a few simple survey modes can simultaneously address a number of frontline science questions. N EAR- EARTH O BU EATS The orbits of many asteroids intersect the orbit of Earth.
|
From page 97... ...
PANEL ON OPTICAL AND INFRARED ASTRONOMY FROM THE GROUND 97 FIGURE 2.9 Orbits for 100 representative near-Earth objects with estimated diameters of I km or more; they represent only about 5 percent ofthe total estimated population in this size range. All orbits included have perihelion distances of 1.10 AU or less, and the orbits have been projected into the Earth-Sun (ecliptic)
|
From page 98... ...
Because their orbital dynamics and compositions carry an imprint of the formation of the solar system, they are arguably the most important missing piece in efforts to understand the formation process. For example, astronomers already have evidence for the injection of comets from the Kuiper Belt and for the ejection of matter to the Oort Cloud and to the interstellar medium.
|
From page 99... ...
If, as Doppler velocity measurements suggest, 1 star in 20 possesses a close-in gas giant planet, then the probability of detecting a planet by occultation is on the order of 5 x 10-5 per star. Because accu99
|
From page 100... ...
will complement studies of the small-scale anisotropy of the microwave background that also measure cosmological parameters such as the density of matter and dark energy. Distant supernovae are also a powerful probe of the history of star formation over cosmic time.
|
From page 101... ...
If, as the MACHO microlensing experiment suggests, an important component of the galactic halo is stellar mass objects of ~0.5 solar masses, the best candidate is a population of very old, very cool, low-luminosity white dwarfs. A deep survey at VRI colors would have the best chance of detecting both those with hydrogen-rich (and infrared Hz-dipole opacitydominated)
|
From page 102... ...
Recent simulations suggest that many local constituents are expected to have temperatures much below 1000 K; as mentioned, these could be too faint for the ongoing 2MASS and Sloan Digital Sky Survey (SDSS) surveys and too rare per unit surface area for infrared surveys covering limited regions of the sky.
|
From page 103... ...
detect and classify variable and moving objects, and (3) place the results in a readily accessible data repository.
|
From page 104... ...
WAVE will provide unprecedented access to the theater of the sky and will pay tremendous dividends for a wide variety of scientific objectives beyond the ones mentioned here. The benefit of a continuous, deep, O/IR sky survey to future space missions and ground-based radio astronomy should be considerable.
|
From page 105... ...
The data repository costs will depend on the degree of synergy with the National Virtual Observatory and the amount of user support provided. Based on experience gleaned from the microlensing projects, the panel estimates that the volume of reduced data will be roughly onetenth the volume of the raw image data.
|
From page 106... ...
Furthermore, they would form an integral piece of the proposed National Virtual Observatory a multiwavelength assemblage of archives from many space- and ground-based observatories with the tools to exploit the total dataset. The project will generate ~ 1 TB of data every night that will have to be reduced in near real time.
|
From page 107... ...
However, these facilities have traditionally not worked together as a coherent system, in contrast with astronomy facilities abroad, which are dominated by national or international observatories. The panel believes that better coordination and cooperation are essential to realizing the full potential of this system and that NSF should work to achieve such coordination and to ensure that facilities and data are made widely available to the entire astronomy community.
|
From page 108... ...
Compile observations of all supernovae to study the history of star formation rates over a range of galaxy types and luminosities (see Figure 2.103. Instrumentation required: high-sensitivity optical and near-IA, low- to moderate-resolution spectrographs fed by AO systems.
|
From page 109... ...
It is significant that despite the high rates of star formation, Lyman-alpha is seen in emission only about half ofthe time, as is the case here. Such spectra, which can now be obtained routinely (with a few hours' worth of integration)
|
From page 110... ...
Adaptive optics with spectroscopy will provide spatially resolved spectra of the atmospheres of Jovian planets. Measure the binary frequency of KBOs and obtain spectra of brighter objects to study composition.
|
From page 111... ...
However, the panel believes that NSF's already important role can become even more important in the coming decade if it enables national and independent observatories to work together, as a single system, to accomplish the scientific goals described in this chapter. Through a process of peer review, NSF can use its grants programs to focus limited federal resources in a way that will maximize the scientific return on these huge investments by supporting the development of instrumentation that provides special, as yet unavailable observing opportunities.
|
From page 112... ...
It is important to recognize that private facilities now support a large fraction of the U.S. astronomy community (~50 percent, according to the NRC report Federal Funding of Astronomical Researchi2)
|
From page 113... ...
· In lieu of some or all of the telescope time, proposals may be accepted that offer other comparable benefits to the astronomy community, for example, the production and dissemination of surveys and the archiving of data from this or other instruments on the telescope for which the instrument is proposed. The panel considers the 50/50 split to be an essential part of its guidelines.
|
From page 114... ...
On the other hand, an unrestricted NSF grant of funds with no benefit provided to the broader astronomy community would frustrate the aspirations of the scientists who would like to use the unique facilities outside the national observatories. Something for both groups is the only appropriate solution; the 50/50 split has the added benefit of conveying the traditional notion of fairness.
|
From page 115... ...
The goal of building a more cohesive ground-based O/IR community with increased incentives for private fund-raising, continued commitment to allowing public access to premier facilities, and maximized scientific creativity and output should guide NSF policy through115 0.2 0 -0.2 `RA from Sgr A* (arcsec)
|
From page 116... ...
astronomers will not be able to continue to play their leadership role in the most basic astronomical research and will not be able to take full advantage of the powerful new space telescopes such as Chandra, SIRTF, and NGST. TECHNOLOGY ISSUES The NSF could enhance the system of O/IR facilities through continued investment in the development of technologies that will ultimately enable new capabilities.
|
From page 117... ...
The development of archives for ground-based data represents a critical link between the independent observatories and the larger astronomy community. The NSF should explore (through NOAO)
|
From page 118... ...
· In addition to facilities that would target capabilities such as synoptic imaging, there is a need for supporting the specialized but limited projects that have been using the smaller national telescopes, for example, the spectroscopic monitoring of relatively bright stars for periodic and episodic activity, observations that are important for the theoretical modeling of stellar interiors and atmospheres. Recognizing that many important programs can be carried out with telescopes of modest aperture and that NOAO is likely to provide fewer such facilities in the future, the panel urges NSF to seek alternative means of supporting them for example, by buying observing time at independent observatories or funding the development of specialized instrumentation.
|
From page 119... ...
The panel urges both agencies to provide adequate support for the vital laboratory studies upon which so much astronomical work is based. ACRONYMS AND ABBREVIATIONS 2MASS Two Micron All Sky Survey AGE asymptotic giant branch AGN active galactic nuclei ALMA Atacama Large Millimeter Array AO adaptive optics ATI Advanced Technologies and Instrumentation (an NSF program)
|
From page 120... ...
MT million tons of TNT, a unit of energy NASA National Aeronautics and Space Administration Origins a NASA program NEO near-Earth object NGST Next Generation Space Telescope NICMOS the near-infrared camera and multiobject spectrometer on the Hubble Space Telescope NOAO National Optical Astronomy Observatories NRC National Research Council NSF National Science Foundation NVO National Virtual Observatory O/IR opticaVinfrared QSO quasi-stellar object OWL Over~vhelmingly Large Telescope or Observatory at a World Level, an ESO proposal for a 100-m telescope SDSS Sloan Digital Sky Survey
|
From page 121... ...
PANEL ON OPTICAL AND INFRARED ASTRONOMY FROM THE GROUND SIM Space Interferometry Mission SIRTF Space Infrared Telescope Facility SMA Submillimeter Array TSIP Telescope System Implementation Program VLT Very Large Telescope VRI observations through visual, red, and infrared filters WAVE Wide Area Variability Experiment WIYN observatory run by the University of Wisconsin, Indiana University, Yale University, and NOAO 121
|
From page 122... ...
The Expanded VLA (EVLA) will uniquely distinguish between massive star formation and accretion onto a supermassive black hole as the underlying energy source, allowing us to decode the history of star and galaxy formation as well as the role of supermassive black holes in galaxy evolution.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.