476 citations · 10.1k across the 164 of their papers we have counts for
47 papers · 1 filter
The prospects of finding the first quasars in the universe
Dominik R. G. Schleicher, Marco Spaans, Ralf S. Klessen
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 obs…
High-resolution HNC 3-2 SMA observations of Arp220
S. Aalto, D. Wilner, M. Spaans +4
We present high resolution (0."4) observations of HNC J=3-2 with the SubMillimeter Array (SMA). We find luminous HNC 3-2 line emission in the western part of Arp220, centered on th…
Rotational Line Emission from Water in Protoplanetary Disks
R. Meijerink, D. R. Poelman, M. Spaans +2
Circumstellar disks provide the material reservoir for the growth of young stars and for planet formation. We combine a high-level radiative transfer program with a thermal-chemica…
Mechanical feedback in the molecular ISM of luminous IR galaxies
A. F. Loenen, M. Spaans, W. A. Baan +1
Aims: Molecular emission lines originating in the nuclei of luminous infra-red galaxies are used to determine the physical properties of the nuclear ISM in these systems. Methods:…
Spitzer's mid-infrared view on an outer Galaxy Infrared Dark Cloud candidate toward NGC 7538
W. F. Frieswijk, M. Spaans, R. F. Shipman +3
Infrared Dark Clouds (IRDCs) represent the earliest observed stages of clustered star formation, characterized by large column densities of cold and dense molecular material observ…
Interstellar Chemistry: Radiation, Dust and Metals
M. Spaans
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 radi…
The Molecular Hydrogen Explorer H2EX
F. Boulanger, J. P. Maillard, P. Appleton +12
The Molecular Hydrogen Explorer, H2EX, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations. The miss…
Monte Carlo simulation of particle interactions at high dynamic range: Advancing beyond the Googol
C. W. Ormel, M. Spaans
We present a method which extends Monte Carlo studies to situations that require a large dynamic range in particle number. The underlying idea is that, in order to calculate the co…
On the Detection of High Redshift Black Holes with ALMA through CO and H2 Emission
M. Spaans, R Meijerink
Many present-day galaxies are known to harbor supermassive, >10^6 Mo, black holes. These central black holes must have grown through accretion from less massive seeds in the early…
The irradiated ISM of ULIRGs
M. Spaans, R. Meijerink, F. P. Israel +2
The nuclei of ULIRGs harbor massive young stars, an accreting central black hole, or both. Results are presented for molecular gas that is exposed to X-rays (1-100 keV, XDRs) and f…
Molecular properties of (U)LIRGs: CO, HCN, HNC and HCO+
A. F. Loenen, W. A. Baan, M. Spaans
The observed molecular properties of a sample of FIR-luminous and OH megamaser (OH-MM) galaxies have been investigated. The ratio of high and low-density tracer lines is found to b…
Physical Characteristics of a Dark Cloud in an Early Stage of Star Formation toward NGC 7538: an Outer Galaxy Infrared Dark Cloud?
Wilfred W. F. Frieswijk, Marco Spaans, Russell F. Shipman +2
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 de…
The James Clerk Maxwell Telescope Legacy Survey of Nearby Star-forming Regions in the Gould Belt
D. Ward-Thompson, J. Di Francesco, J. Hatchell +59
This paper describes a James Clerk Maxwell Telescope (JCMT) legacy survey that has been awarded roughly 500 hrs of observing time to be carried out from 2007 to 2009. In this surve…
CO+ in M 82: A Consequence of Irradiation by X-rays
M. Spaans, R. Meijerink
Based on its strong CO+ emission it is argued that the M 82 star-burst galaxy is exposed to a combination of FUV and X-ray radiation. The latter is likely to be the result of the s…
A PDR-Code Comparison Study
M. Roellig, N. P. Abel, T. Bell +21
We present a comparison between independent computer codes, modeling the physics and chemistry of interstellar photon dominated regions (PDRs). Our goal was to understand the mutua…
The interpretation of water emission from dense interstellar clouds
D. R. Poelman, M. Spaans, A. G. G. M. Tielens
Context: Existing SWAS observations and future HIFI/Herschel data require a clear sense of the information content of water emission and absorption lines. Aims: Investigate wether…
Overluminous HNC Line Emission in Arp220, NGC4418 and Mrk231 - Global IR Pumping or XDRs?
S. Aalto, M. Spaans, M. C. Wiedner +1
We find that the HNC J=3-2 emission is brighter than the HCN 3-2 emission by factors of 1.5 to 2.3 in the ultraluminous mergers Arp220 and Mrk231 and the luminous IR galaxy NGC4418…
The JCMT Spectral Legacy Survey
R. Plume, G. A. Fuller, F. Helmich +30
Stars form in the densest, coldest, most quiescent regions of molecular clouds. Molecules provide the only probes which can reveal the dynamics, physics, chemistry and evolution of…
The Stellar Mass Spectrum in Warm and Dusty Gas: Deviations from Salpeter in the Galactic Centre and in Circum-Nuclear Starburst Regions
Ralf S. Klessen, Marco Spaans, Anne-Katharina Jappsen
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…
Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models
R. Meijerink, M. Spaans, F. P. Israel
\abridged The nuclei of active galaxies harbor massive young stars, an accreting central black hole, or both. In order to determine the physical conditions that pertain to molecula…
Dust coagulation in protoplanetary disks: porosity matters
C. W. Ormel, M. Spaans, A. G. G. M. Tielens
Context: Sticking of colliding dust particles through van der Waals forces is the first stage in the grain growth process in protoplanetary disks, eventually leading to the formati…
Irradiated ISM: Discriminating between Cosmic Rays and X-rays
R. Meijerink, M. Spaans, F. P. Israel
The ISM of active galaxy centers is exposed to a combination of cosmic ray, FUV and X-ray radiation. We apply PDR models to this ISM with both `normal' and highly elevated (5\times…
Diagnostics of active galaxies: I. Modeling the infrared properties of dusty cores of starburst galaxies
A. F. Loenen, W. A. Baan, M. Spaans
An evolutionary model of star formation in ULIRGs was created using existing star formation and radiative transfer codes (STARBURST99, RADMC and RADICAL) as building blocks. The re…
Line profiles of water for the photon dominated region and embedded sources in the S140 region
D. R. Poelman, M. Spaans
A radiative transfer method for the treatment of molecular lines is presented. We apply this method to previous SWAS and ISO observations of water vapor in the source S140 in order…