Search

Current and future optical technologies will aid exploration of the Moon and Mars while advancing fundamental physics research in the solar system. Technologies and possible improvements in the laser-enabled tests of various physical phenomena are considered along with a space architecture that could be the cornerstone for robotic and human exploration of the solar system. In particular, accurate ranging to the Moon and Mars would not only lead to construction of a new space communication infrastructure enabling an improved navigational accuracy, but will also provide a significant improvement in several tests of gravitational theory: the equivalence principle, geodetic precession, PPN parameters $\beta$ and $\gamma$, and possible variation of the gravitational constant $G$. Other tests would become possible with an optical architecture that would allow proceeding from meter to centimeter to millimeter range accuracies on interplanetary distances. This paper discusses the current state and the future improvements in the tests of relativistic gravity with Lunar Laser Ranging (LLR). We also consider precision gravitational tests with the future laser ranging to Mars and discuss optical design of the proposed Laser Astrometric Test of Relativity (LATOR) mission. We emphasize that already existing capabilities can offer significant improvements not only in the tests of fundamental physics, but may also establish the infrastructure for space exploration in the near future. Looking to future exploration, what characteristics are desired for the next generation of ranging devices, what is the optimal architecture that would benefit both space exploration and fundamental physics, and what fundamental questions can be investigated? We try to answer these questions., Comment: 37 pages, 9 figures, 1 table. Invited talk given at ``The 2004 NASA/JPL Workshop on Physics for Planetary Exploration.'' April 20-22, 2004, Solvang, CA

This paper addresses the motivation, technology and recent results in the tests of the general theory of relativity (GR) in the solar system. We specifically discuss Lunar Laser Ranging (LLR), the only technique available to test the Strong Equivalence Principle (SEP) and presently the most accurate method to test for the constancy of the gravitational constant, G. The new Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) will enable tests of the Weak and Strong Equivalence Principles with a sensitivity approaching 10e-14, translating to a test of the SEP violation parameter, \eta, to a precision of ~3x10e-5. In addition, the (v/c)^2 general relativistic effects would be tested to better than 0.1%, and measurements of the relative change in the gravitational constant, \dot{G}/G, would be ~0.1% the inverse age of the universe. We also discuss the Laser Astrometric Test Of Relativity (LATOR) mission that will be able to improve the value of the PPN parameter \gamma to accuracy of 1 part in 10e8 and will measure effects of the next post-Newtonian order (1/c^4) of light deflection resulting from gravity's intrinsic non-linearity, as well as measure a variety of other relativistic effects. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could discover a violation or extension of GR, or reveal the presence of an additional long range interaction in the physical law. There are no analogs to the LATOR experiment; it is unique and is a natural culmination of solar system gravity experiments., Comment: 20 pages, 3 figures, invited talk presented at 302.WE-Heraeus-Seminar: "Astrophysics, Clocks and Fundamental Constants", 16-18 June 2003. The Physikzentrum, Bad Honnef, Germany

Accurate analysis of precision ranges to the Moon has provided several tests of gravitational theory including the Equivalence Principle, geodetic precession, parameterized post-Newtonian (PPN) parameters $\gamma$ and $\beta$, and the constancy of the gravitational constant {\it G}. Since the beginning of the experiment in 1969, the uncertainties of these tests have decreased considerably as data accuracies have improved and data time span has lengthened. We are exploring the modeling improvements necessary to proceed from cm to mm range accuracies enabled by the new Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) currently under development in New Mexico. This facility will be able to make a significant contribution to the solar system tests of fundamental and gravitational physics. In particular, the Weak and Strong Equivalence Principle tests would have a sensitivity approaching 10$^{-14}$, yielding sensitivity for the SEP violation parameter $\eta$ of $\sim 3\times 10^{-5}$, $v^2/c^2$ general relativistic effects would be tested to better than 0.1%, and measurements of the relative change in the gravitational constant, $\dot{G}/G$, would be $\sim0.1$% the inverse age of the universe. Having this expected accuracy in mind, we discusses the current techniques, methods and existing physical models used to process the LLR data. We also identify the challenges for modeling and data analysis that the LLR community faces today in order to take full advantage of the new APOLLO ranging station., Comment: 15 pages, 3 figures, talk presented at 2003 NASA/JPL Workshop on Fundamental Physics in Space, April 14-16, 2003, Oxnard, CA

The Palomar Integral Field Spectrograph was used to probe a variety of environments in nine nearby galaxies that span a range of morphological types, luminosities, metallicities, and infrared-to-blue ratios. For the first time, near-infrared spectroscopy was obtained for nuclear or bright HII regions in star-forming galaxies over two spatial dimensions (5.7"x10.0") in the [FeII] (1.257um), [FeII] (1.644um), Paschen beta (1.282um), H2 (2.122um), and Brackett gamma (2.166um) transition lines. These data yield constraints on various characteristics of the star-forming episodes in these regions, including their strength, maturity, spatial variability, and extinction. The HII regions stand out from the nuclei. Unlike observations of nuclear regions, HII region near-infrared observations do not show a spatial coincidence of the line and continuum emission; the continuum and line maps of HII regions usually show distinct and sometimes spatially-separated morphologies. Gauging from Paschen beta and Brackett gamma equivalent widths and luminosities, the HII regions have younger episodes of star formation than the nuclei and more intense radiation fields. Near-infrared line ratio diagnostics suggest that HII regions have "purer" starbursting properties. The correlation between ionizing photon density and mid-infrared color is consistent with the star formation activity level being higher for HII regions than for nuclei. And though the interpretation is complicated, on a purely empirical basis the HII regions show lower Fe1+ abundances than nuclei by an order of magnitude., Comment: 37 pages including 13 figures; accepted for publication in the Astrophysical Journal

We present near-infrared imaging and spectroscopic observations of two FR II high-redshift radio galaxies (HzRGs), 4C 40.36 (z=2.3) and 4C 39.37 (z=3.2), obtained with the Hubble, Keck, and Hale Telescopes. High resolution images were taken with filters both in and out of strong emission lines, and together with the spectroscopic data, the properties of the line and continuum emissions were carefully analyzed. Our analysis of 4C 40.36 and 4C 39.37 shows that strong emission lines (e.g., [O III] 5007 A and H alpha+[N II]) contribute to the broad-band fluxes much more significantly than previously estimated (80% vs. 20-40%), and that when the continuum sources are imaged through line-free filters, they show an extremely compact morphology with a high surface brightness. If we use the R^1/4-law parametrization, their effective radii (r(e)) are only 2-3 kpc while their restframe B-band surface brightnesses at r(e) are I(B) ~ 18 mag/arcsec^2. Compared with z ~ 1 3CR radio galaxies, the former is x3-5 smaller, while the latter is 1-1.5 mag brighter than what is predicted from the I(B)-r(e) correlation. Although exponential profiles produce equally good fits for 4C 40.36 and 4C 39.37, this clearly indicates that with respect to the z~1 3CR radio galaxies, the light distribution of these two HzRGs is much more centrally concentrated. Spectroscopically, 4C 40.36 shows a flat (fnu=const) continuum while 4C 39.37 shows a spectrum as red as that of a local giant elliptical galaxy. Although this difference may be explained in terms of a varying degree of star formation, the similarities of their surface brightness profiles and the submillimeter detection of 4C 39.37 might suggest that the intrinsic spectra is equally blue (young stars or an AGN), and that the difference is the amount of reddening., Comment: 30 pages, 6 tables, 10 figures; Accepted for publication in Astronomical Journal

Imaging spectroscopy using the new Palomar Integral Field Spectrograph is presented for the Pa-alpha line in four ultraluminous infrared galaxies. In most cases, we are able to establish the geometry of the merger, and thus estimate the time in the merger process at which we are viewing the system. The resulting range in estimated ages, some of which are very young encounters (~5x10^7 yr), is not predicted by merger models, which produce high rates of star formation either 1-2x10^8 years after the first encounter or very late (~10^9 yr) in the merger process. Even in the very young mergers, the ultraluminous activity appears to be centrally concentrated on the nucleus of one of the progenitor galaxies---namely the galaxy with a prograde orbital geometry. Very high star formation rates (2-5 M_sun/yr) are also observed in structures believed to be newly formed tidal tails. The presence of a significant population of very young ultraluminous mergers, together with the majority of ultraluminous infrared galaxies existing in the final stages of merger activity, indicates that the ultraluminous galaxy phase is at least bimodal in time. An evolutionary scenario is proposed for ultraluminous infrared galaxies, wherein the far-infrared luminosity may undergo multiple ultraluminous bursts during the course of the encounter. A substantial fraction of the merger lifetime may be spent in a phase identified with the less powerful luminous infrared galaxy class., Comment: 27 pages, 21 figures, 5 in color, uses AASTeX 5.02 & emulateapj5.sty; To appear in the Astrophysical Journal

We present near-infrared spectroscopy for a complete sample of 33 ultraluminous infrared galaxies at a resolution of R\approx 1000. Most of the wavelength range from 1.80-2.20 microns in the rest frame is covered, including the Pa-alpha and Br-gamma hydrogen recombination lines, and the molecular hydrogen vibration-rotation 1-0 S(1) and S(3) lines. Other species, such as He I, [Fe II], and [Si VI] appear in the spectra as well, in addition to a number of weaker molecular hydrogen lines. Nuclear extractions for each of the individual galaxies are presented here, along with spectra of secondary nuclei, where available. The Pa-alpha emission is seen to be highly concentrated on the nuclei, typically with very little emision extending beyond a radius of 1 kpc. Signatures of active nuclei are rare in the present sample, occurring in only two of the 33 galaxies. It is found that visual extinctions to the nuclei via the Pa-alpha/Br-gamma line ratio in excess of 10 magnitudes are relatively common among ULIRGs, and that visual extinctions greater than 25 mag are necessary to conceal a QSO emitting half the total bolometric luminosity. The vibration-rotation lines of molecular hydrogen appear to be predominantly thermal in origin, with effective temperatures generally around 2200 K. The relative nuclear velocities between double nucleus ULIRGs are investigated, through which it is inferred that the maximum deprojected velocity difference is about 200 km/s. This figure is lower than the velocities predicted by physical models of strong interactions/mergers of large, gas-rich galaxies., Comment: 52 pages (19 with just figures), 9 figures, accepted for publication in the Astronomical Journal; Table 3 not formatted properly on astro-ph: get source and print Murphy.tab3.ps

Near-infrared spectroscopy using the new Palomar Integral Field Spectrograph indicates the presence of an AGN (active galactic nucleus) in the ultraluminous infrared galaxy IRAS 08311-2459. The high-velocity wings of the Paschen-alpha hydrogen recombination line are seen to be spatially unresolved, and with no positional offset between red and blue high velocity emission. The [Si VI] coronal line, with a 167 eV excitation potential, is also spatially unresolved with a velocity width comparable to that of the broad component of the Pa-alpha emission. The low velocity component of the Pa-alpha emission is seen to be rotating, and is extended over about 2 kpc. Molecular hydrogen is also extended, and elongated along the maximum velocity gradient, sharing the same rotation profile as the narrow Pa-alpha emission. The simple picture in agreement with the observations is that of an AGN surrounded by a rotating disk of star formation. These observations lend strength to the usage of [Si VI] as a diagnostic of AGN activity in ultraluminous infrared galaxies, and also highlight the utility of integral field spectroscopy in elucidating subtle morphological differences in line emitting regions., Comment: 18 pages, 7 figures (fig. 7 color), AASTeX v5.0, accepted for publ. in AJ

We present Keck high-resolution near-IR (2.2 microns; FWHM~0.15") and mid-IR (12.5 microns; FWHM~0.4") images of APM08279+5255, a z=3.91 IR-luminous BALQSO with a prodigious apparent bolometric luminosity of 5x10^{15} Lsun, the largest known in the universe. The K-band image shows that this system consists of three components, all of which are likely to be the gravitationally lensed images of the same background object, and the 12.5 micron image shows a morphology consistent with such an image configuration. Our lens model suggests that the magnification factor is ~100 from the restframe UV to mid-IR, where most of the luminosity is released. The intrinsic bolometric luminosity and IR luminosity of APM08279+5255 are estimated to be 5x10^{13} Lsun and 1x10^{13} Lsun, respectively. This indicates that APM 08279+5255 is intriniscally luminous, but it is not the most luminous object known. As for its dust contents, little can be determined with the currently available data due to the uncertainties associated with the dust emissivity and the possible effects of differential magnification. We also suggest that the lensing galaxy is likely to be a massive galaxy at z~3., Comment: 32 pages, 4 tables, 11 figures; Accepted for publication in ApJ

Using NICMOS on HST, we have imaged the emission-line nebulae and the line-free continuum in 4C 40.36, a ultra-steep spectrum FR II radio galaxy at z=2.269. The line-free continuum was found to be extremely compact and symmetric while the emission-line nebulae seen in H-alpha+[N II] show very clumpy structures spreading almost linearly over 16 kpc. However, this linear structure is clearly misaligned from the radio axis. The SED of the line-free continuum is very flat, suggesting that if the continuum emission is produced by a single source, it is likely to be a young bursting stellar population or scattered AGN light. However, because of the lack of a line-free optical image with a comparable spatial resolution, we cannot exclude the possibility that the observed SED is a composite of a young blue population and an old red population., Comment: 4 pages, 2 figures; to appear in the proceedings of "The Hy-Redshift Universe: Galaxy Formation and Evolution at High Redshift", eds. A.J.Bunker and W. J. M. van Breugel

Near infrared spectra with resolution R ~ 1100 in the rest wavelength range 1.8-2.2 microns have been obtained for a complete sample of 33 ultraluminous infrared galaxies. Of the 33 objects observed, 2 show evidence of a central AGN through either a broad Paschen-alpha line or emission in the 1.963 micron fine structure of [Si VI]. In the median spectrum of the remaining 31 objects, the lines present are recombination lines of Hydrogen, neutral Helium, vibration-rotation lines of H_2, and [Fe II]. There is no indication of AGN activity in the median spectrum, either through broad atomic recombination lines or high ionization lines. No trends in luminosity are apparent when subsets of the 31 non-AGN ULIRGs are binned by luminosity and median combined. When secondary nuclei exist in ULIRGs, they typically have spectra very much like those seen in the primary nuclei., Comment: 3 figures

We present near-infrared medium-resolution ($R \sim 875$) spectra of the microquasar GRS 1915+105 on 1997 August 13-15 UTC from the Hale 200-inch telescope. The spectra showed broad emission lines of He I (2.058 $\mu$m) and H I (2.166 $\mu$m - Br$\gamma$), consistent with previous work. On August 14 UTC, we took spectra with $\sim 6$-minute time resolution during infrared flaring events similar to those reported in Eikenberry et al. (1998a), which appear to reveal plasma ejection from the system. During the flares, the emission line fluxes varied in approximately linear proportionality to the IR continuum flux, implying that the lines are radiatively pumped by the flares. We also detected a weak He II (2.189 $\mu$m) emission line on August 14 UTC. The nature of the line variability and the presence of the He II feature indicate that the emission lines in GRS 1915+105 arise in an accretion disk around the compact object, rather than in the circumstellar disk of a proposed Oe/Be companion. The radiative line pumping also implies that the flare emission originates from ejecta which have moved out of the accretion disk plane., Comment: 13 pages plus 4 figures, to appear in ApJ Letters

We have imaged the z=3.594 radio galaxy 4C +19.71 in the light of the redshifted [OIII] 5007 angstrom emission line, using a narrow-band filter centered at 2.3 microns with the Near Infrared Camera on the Keck Telescope. The [OIII] nebula of 4C +19.71 has a size of 74 x 9 kpc, and a luminosity of 3 x 10^37 W. The rest frame equivalent width of the 5007 line, averaged over the entire nebula, is 560 angstroms. The length of the major axis of the [OIII] emission is nearly identical to the separation of the radio lobes seen at 1465 MHz (Rottgering, et al. 1994), and the position angle of the nebula is the same as that of the two radio lobes. In addition, 4C +19.71 follows the optical emission line vs. radio power correlation seen in other powerful radio galaxies. The [OIII] and Lyman alpha emission line luminosities suggest that the ionized gas mass lies in the range of 2 x 10^8 - 10^9 solar masses. The O/H ratio in the nebula is at least a few tenths solar, and may be as high as a factor of three above solar, indicating a previous phase of star formation in 4C +19.71. Thirty five percent of the total K-band flux is contributed by the 5007 angstrom emission line, and the continuum of 4C +19.71 has a K=19.6 mag. This places 4C +19.71 along the K-z relation found for other radio galaxies and radio loud quasars. If the continuum is dominated by starlight, the host galaxy has a rest frame visual luminosity of about 40L*. There are no candidate emission-line objects at the redshift of 4C +19.71 having [OIII] rest frame equivalent widths of more than about 2% that of the radio galaxy itself within a volume of 212 cubic Mpc., Comment: plain LaTex with 3 postscript figures. ApJ accepted