arXiv subjects

Robert O'Connell

Publications and source records attributed to Robert O'Connell.

23 records · Page 2Linked to original sources

arXiv2009

The Magellanic Clouds Survey: a Bridge to Nearby Galaxies

We outline to the community the value of a Magellanic Clouds Survey that consists of three components: I) a complete-area, high resolution, multi-band UV-near-IR broadband survey; II) a narrowband survey in 7 key nebular filters to cover a statistically significant sample of representative HII regions and a large-area, contiguous survey of the diffuse, warm ISM; and III) a comprehensive FUV spectroscopic survey of 1300 early-type stars. The science areas enabled by such a dataset are as follows: A) assessment of massive star feedback in both HII regions and the diffuse, warm ISM; B) completion of a comprehensive study of the 30 Doradus giant extragalactic HII region (GEHR); C) development and quantitative parameterization of stellar clustering properties; D) extensive FUV studies of early-type stellar atmospheres and their energy distributions; and E) similarly extensive FUV absorption-line studies of molecular cloud structure and ISM extinction properties. These data will also allow a number of additional studies relating to the underlying stellar populations.

astro-ph.CO↗

arXiv2009

The Star Formation Camera

The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, and to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. This program addresses the origins and evolution of stars, galaxies, and cosmic structure and has direct relevance for the formation and survival of planetary systems like our Solar System and planets like Earth. We present the design and performance specifications resulting from the implementation study of the camera, conducted under NASA's Astrophysics Strategic Mission Concept Studies program, which is intended to assemble realistic options for mission development over the next decade. The result is an extraordinarily capable instrument that will provide deep, high-resolution imaging across a very wide field enabling a great variety of community science as well as completing the core survey science that drives the design of the camera. The technology associated with the camera is next generation but still relatively high TRL, allowing a low-risk solution with moderate technology development investment over the next 10 years. We estimate the cost of the instrument to be $390M FY08.

astro-ph.IM↗

arXiv2009

Understanding Global Galactic Star Formation

We propose to the community a comprehensive UV/optical/NIR imaging survey of Galactic star formation regions to probe all aspects of the star formation process. The primary goal of such a study is to understand the evolution of circumstellar protoplanetary disks and other detailed aspects of star formation in a wide variety of different environments. This requires a comprehensive emission-line survey of nearby star-forming regions in the Milky Way, where a high spatial resolution telescope+camera will be capable of resolving circumstellar material and shock structures. In addition to resolving circumstellar disks themselves, such observations will study shocks in the jets and outflows from young stars, which are probes of accretion in the youngest protoplanetary disks still embedded in their surrounding molecular clouds. These data will allow the measurement of proper motions for a large sample of stars and jets/shocks in massive star-forming regions for the first time, opening a new window to study the dynamics of these environments. It will require better than 30 mas resolution and a stable PSF to conduct precision astrometry and photometry of stars and nebulae. Such data will allow production of precise color-color and color magnitude diagrams for millions of young stars to study their evolutionary states. One can also determine stellar rotation, multiplicity, and clustering statistics as functions of environment and location in the Galaxy. For the first time we can systematically map the detailed excitation structure of HII regions, stellar winds, supernova remnants, and supershells/superbubbles. This survey will provide the basic data required to understand star formation as a fundamental astrophysical process that controls the evolution of the baryonic contents of the Universe.

astro-ph.GA↗

arXiv2009

A Systematic Study of the Stellar Populations and ISM in Galaxies out to the Virgo Cluster

We present a compelling case for a systematic and comprehensive study of the resolved and unresolved stellar populations, ISM, and immediate environments of galaxies throughout the local volume, defined here as D < 20 Mpc. This volume is our cosmic backyard and the smallest volume that encompasses environments as different as the Virgo, Ursa Major, Fornax and (perhaps) Eridanus clusters of galaxies, a large number and variety of galaxy groups, and several cosmic void regions. In each galaxy, through a pan-chromatic (160--1100nm) set of broad-band and diagnostic narrow-band filters, ISM structures and individual luminous stars to >~1 mag below the TRGB should be resolved on scales of <5 pc (at D <~ 20 Mpc, lambda ~ 800nm, for mu_I >~ 24 mag/arcsec^2 and m_{I,TRGB} <~ 27.5 mag). Resolved and unresolved stellar populations would be analyzed through color-magnitude and color-color diagram fitting and population synthesis modeling of multi-band colors and would yield physical properties such as spatially resolved star formation histories. The ISM within and around each galaxy would be analyzed using key narrow-band filters that distinguish photospheric from shock heating and provide information on the metallicity of the gas. Such a study would finally allow unraveling the global and spatially resolved star formation histories of galaxies, their assembly, satellite systems, and the dependences thereof on local and global environment within a truly representative cosmic volume. The proposed study is not feasible with current instrumentation but argues for a wide-field (>~250 arcmin^2), high-resolution (<~0.020"--0.065" [300--1000nm]), ultraviolet--near-infrared imaging facility on a 4m-class space-based observatory.

astro-ph.CO↗

arXiv2009

Galaxy Assembly and SMBH/AGN-growth from Cosmic Dawn to the End of Reionization

[abridged] We propose a tiered, UV--near-IR, cosmological broad- and medium-band imaging and grism survey that covers ~10 deg^2 in two epochs to m_AB=28, ~3 deg^2 in seven epochs to m_AB=28, and ~1 deg^2 in 20 epochs to m_AB=30 mag. Such a survey is an essential complement to JWST surveys (<~0.1 deg^2 to m_AB<~31 mag at lambda>1100nm and z>~8). We aim to: (1) understand in how galaxies formed from perturbations in the primordial density field by studying faint Lyα-emitting and Lyman-break galaxies at 5.5<~z<~8 and trace the metal-enrichment of the IGM; (2) measure the evolution of the faint end of the galaxy luminosity function (LF) from z~8 to z~0 by mapping the ramp-up of PopII star formation, (dwarf) galaxy formation and assembly, and hence, the objects that likely completed the H-reionization at z~6; (3) directly study the lambda<91.2nm escape fractions of galaxies and weak AGN from z~4.0--2.5, when the He reionization finished; (4) measure the mass- and environment-dependent galaxy assembly process from z~5 to z~0, combining accurate (sigma_z/(1+z) <~ 0.02) photo-z's with spatially resolved stellar populations and kpc-scale structure for >~5x10^6 galaxies; (5) trace the strongly epoch-dependent galaxy merger rate and constrain how Dark Energy affected galaxy assembly and the growth of SMBHs; (6) study >~10^5 weak AGN/feeding SMBHs in the faint-end of the QSO LF, over 10 deg^2 and measure how the growth of SMBHs kept pace with galaxy assembly and spheroid growth, and how this process was shaped by various feedback processes over cosmic times since z~8. The proposed study is not feasible with current instrumentation but argues for a wide-field (>~250 arcmin^2), high-resolution (<~0.02--0.11 [300--1700 nm]), UV--near-IR imaging facility on a 4m-class space observatory.

astro-ph.CO↗