Molecular Gas Disk Structures around AGNs (2009)
Wada, Keiichi, Papadopoulos, Padeli, Spaans, Marco
We present new high resolution numerical simulations of the ISM in a central R ~32 parsecs region around a supermassive black hole at a galactic center. Three-dimensional hydrodynamic modeling of the...
P-Cygni Profiles of Molecular Lines toward Arp 220 Nuclei (2009)
Sakamoto, Kazushi, Aalto, Susanne, Wilner, David J., Black, John H., Conway, John E., Costagliola, Francesco, ...
We report ~100 pc (0.3") resolution observations of (sub)millimeter HCO+ and CO lines in the ultraluminous infrared galaxy Arp 220. The lines peak at two merger nuclei, with HCO+ being more spatially...
Chemical stratification in the Orion Bar: JCMT Spectral Legacy Survey observations (2009)
Ossenkopf, Volker, Spaans, Marco, Roberts, Helen, Fuller, Gary A., ...
Photon-dominated regions (PDRs) are expected to show a layered structure in molecular abundances and emerging line emission, which is sensitive to the physical structure of the region as well as the...
The prospects of finding the first quasars in the universe (2008)
Schleicher, Dominik R. G., Spaans, Marco, Klessen, Ralf S.
We study the prospects of finding the first quasars in the universe with ALMA and JWST. For this purpose, we derive a model for the high-redshift black hole population based on observed relations...
Interstellar Chemistry: Radiation, Dust and Metals (2008)
An overview is given of the chemical processes that occur in primordial systems under the influence of radiation, metal abundances and dust surface reactions. It is found that radiative feedback...
Frieswijk, Wilfred W. F., Spaans, Marco, Shipman, Russell F., Teyssier, David, Hily-Blant, Pierre
In the inner parts of the Galaxy the Infrared Dark Clouds (IRDCs) are presently believed to be the progenitors of massive stars and star clusters. Many of them are predominantly devoid of active star...
Klessen, Ralf S., Spaans, Marco, Jappsen, Anne-Katharina
Understanding the origin of stellar masses is a key problem in astrophysics. In the solar neighborhood, the mass distribution of stars follows a seemingly universal pattern. In the centre of the...
Pregalactic Black Hole Formation with an Atomic Hydrogen Equation of State (2006)
The polytropic equation of state of an atomic hydrogen gas is examined for primordial halos with baryonic masses of M_h~10^7-10^9 Mo. For roughly isothermal collapse around 10^4 K, we find that line...
Dijkstra, Mark, Haiman, Zoltan, Spaans, Marco
We present Monte Carlo calculations of Lyman alpha (Lya) radiative transfer through collapsing gas clouds, representing proto-galaxies that are caught in the process of their assembly. Such galaxies...
Lyman Alpha Radiation From Collapsing Protogalaxies II: Observational Evidence for Gas Infall (2005)
Dijkstra, Mark, Haiman, Zoltan, Spaans, Marco
We model the spectra and surface brightness distributions for the Lyman alpha (Lya) radiation expected from protogalaxies that are caught in the early stages of their assembly. We use the results of...
Meijerink, Rowin, Spaans, Marco
We present a far-ultraviolet (PDR) and an X-ray dominated region (XDR) code. We include and discuss thermal and chemical processes that pertain to irradiated gas. An elaborate chemical network is...
Ruiterkamp, Richard, Cox, Nick, Kaper, Lex, Spaans, Marco, Foing, Bernard, Salama, Farid, ...
{Ruiterkamp et al., 2005, Astronomy \& Astrophysics, In press
The Polytropic Equation of State of Primordial Gas Clouds (2004)
The polytropic equation of state (EOS) of primordial gas clouds with modest enrichment is computed, motivated by the recent observations of very Fe-deficient stars, [Fe/H]~10^{-3.5}-10^{-5}, such as...
Chemical Composition of the Early Universe (2003)
A prediction of standard inflationary cosmology is that the elemental composition of the medium out of which the earliest stars and galaxies condensed consisted primarily of hydrogen and helium 4He...
CO emission from high redshift (2001)
Gnedin, Nickolay Y., Silk, Joseph, Spaans, Marco
Future observations with ALMA will be able to detect star-forming primordial gal axies, and perhaps even their dwarf spheroidal satellites, in CO emission lines at redshifts approaching 10. These...
The Abundance and Emission of H2O and O2 in Clumpy Molecular Clouds (2000)
Spaans, Marco, Van Dishoeck, Ewine
Recent observations with the Submillimeter Wave Astronomy Satellite indicate abundances of gaseous H2O and O2 in dense molecular clouds which are significantly lower than found in standard...
Wada, Keiichi, Spaans, Marco, Kim, Sungeun
Based on our high resolution, two-dimensional hydrodynamical simulations, we propose that large cavities may be formed by the nonlinear development of the combined thermal and gravitational...
Lyman Alpha Cooling Radiation from High-Redshift Halos (2000)
Haiman, Zoltan, Spaans, Marco, Quataert, Eliot
The baryons inside high-redshift halos with virial temperatures above T=10^4 K cool radiatively as they condense inside dark matter potential wells. We show that the release of the gravitational...
The Polytropic Equation of State of Interstellar Gas Clouds (2000)
Models are presented for the polytropic equation of state of self-gravitating, quiescent interstellar gas clouds. A detailed analysis, including chemistry, thermal balance, and radiative transfer, is...
On the Topological Nature of Fundamental Interactions (1999)
A thought experiment is proposed to unify quantum mechanics and general relativity. The central paradigm is that space-time {\it topology} is ultimately responsible for the Heisenberg uncertaintly...
Models for High-Redshift Lyman Alpha Emitters (1998)
We present models for dusty high-redshift Lyman alpha emitting galaxies by combining the Press-Schechter formalism with a treatment of inhomogeneous dust distribution inside galaxies. These models...
Kemper, Ciska, Spaans, Marco, Jansen, David J., Hogerheijde, Michiel R., Van Dishoeck, Ewine F.
ISO [C II] 158 micron, [O I] 63 micron, and H_2 9 and 17 micron observations are presented of the reflection nebula Ced 201, which is a photon-dominated region illuminated by a B9.5 star with a color...
Observational Tests to Discern the Topology of Planckian Space-Time (1998)
Observational diagnostics are constructed which reflect the underlying topology of Planckian space-time, and are directly related to phenomena on much larger scales. Specific predictions are made for...
The Molecular ISM in Low Surface Brightness Disk Galaxies (1998)
Mihos, Chris, Spaans, Marco, McGaugh, Stacy
We present models for the interstellar medium in disk galaxies. In particular, we investigate whether the ISM in low surface brightness galaxies can support a significant fraction of molecular gas...
Models for Dusty Lyman alpha Emitters at High Redshift (1998)
Models are presented for the Lyman alpha emission of dusty high-redshift galaxies by combining the Press-Schechter formalism with a treatment of the inhomogeneous dust distribution inside galaxies....
Towards a Topological Formulation of Fundamental Interactions (1998)
A thought experiment is formulated to unify quantum mechanics and general relativity in a topological manner. An analysis of the interactions in Nature is then presented. The universal ground state...
Search for Interstellar Water in the Translucent Molecular Cloud toward HD 154368 (1998)
Spaans, Marco, Neufeld, David, Lepp, Stephen, Melnick, Gary J., Stauffer, John
We report an upper limit of 9 x 10^{12} cm-2 on the column density of water in the translucent cloud along the line of sight toward HD 154368. This result is based upon a search for the C-X band of...
Effective Star Formation Rates for Cosmological Applications (1998)
Spaans, Marco, Carollo, Marcella
Effective star formation rates in tabular form are computed which yield a prescription for the star formation activity in model galaxies as a function of ambient density, metallicity, and stellar...
A Topological Formulation of the Standard Model (1997)
A topological theory for the interactions in Nature is presented. The theory derives from the cyclic properties of the topological manifold Q=2T^3 + 3S^1 x S^2 which has 23 intrinsic degrees of...
Molecular Lines as Diagnostics of High Redshift Objects (1997)
Models are presented for CO rotational line emission by high redshift starburst galaxies. The influence of the cosmic microwave background on the thermal balance and the level populations of atomic...
Molecular Hydrogen in Diffuse Interstellar Clouds of Arbitrary Three-Dimensional Geometry (1997)
Spaans, Marco, Neufeld, David A.
We have constructed three-dimensional models for the equilibrium abundance of molecular hydrogen within diffuse interstellar clouds of arbitrary geometry that are illuminated by ultraviolet...
Topological Dynamics and Grand Unified Theory (1997)
A formalism is presented to construct a non-perturbative Grand Unified Theory when gravitational Planck-scale phenomena are included. The fundamental object on the Planck scale is the three-torus T^3...
Spaans, Marco, Carollo, Marcella
We present models of the cosmological star formation and metal production history of (proto-)galaxies with varying axis ratios. More massive and/or roughly spherical systems reach the...
A Topological Extension of General Relativity (1996)
A set of algebraic equations for the topological properties of space-time is derived, and used to extend general relativity into the Planck domain. A unique basis set of three-dimensional prime...
Molecules at high Redshift: The Evolution of the Cool Phase of Protogalactic Disks (1996)
Norman, Colin A., Spaans, Marco
We study the formation of molecular hydrogen, after the epoch of re-ionization, in the context of canonical galaxy formation theory due to hierarchical clustering. There is an initial epoch of $H_2$...