20 research outputs found
X-raying extragalactic gas: warm-hot gas in the EAGLE simulations
I have studied the hot, diffuse gas around and between galaxies. Specifically, I have used the EAGLE numerical simulations of galaxy formation to predict the properties of this gas, and I have used those properties to predict specific observables: soft X-ray absorption and emission lines. Measuring this gas is challenging, but if we can observe and characterise it, we can learn much about the gas flows in and out of galaxies that regulate their formation and evolution. Observations of soft X-ray lines with future X-ray telescopes, such as Athena and XRISM, will enable us to do so. For these future X-ray telescopes, the strongest X-ray absorption lines and essentially all detectable line emission will come from the gaseous haloes surrounding galaxies. Some weaker, but still detectable absorption lines will come from the more diffuse gas outside these haloes. Photo-ionisation by the intergalactic ultraviolet/X-ray radiation background affects the absorption and emission lines of the very diffuse gas between galaxies, and the diffuse edges of the galaxy haloes. Emission from this photo-ionised gas is not expected to be detectable, but some absorption should be.Galaxie
The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray-line emission
Galaxie
The warm-hot circumgalactic medium around EAGLE-simulation galaxies and its detection prospects with X-ray and UV line absorption
Large scale structure and cosmolog
Ionization by galaxy cluster photons alters the ionization state of the nearby warm-hot intergalactic medium
Galaxie
Galaxy cluster photons alter the ionization state of the nearby warm-hot intergalactic medium
High Energy Astrophysic
Constraining the redshift of featureless Blazar 1ES 1553+113 and implications For the WHIM
Large scale structure and cosmolog
Observing the First Stars and Black Holes
The high sensitivity of JWST will open a new window on the end of the
cosmological dark ages. Small stellar clusters, with a stellar mass of several
10^6 M_sun, and low-mass black holes (BHs), with a mass of several 10^5 M_sun
should be directly detectable out to redshift z=10, and individual supernovae
(SNe) and gamma ray burst (GRB) afterglows are bright enough to be visible
beyond this redshift. Dense primordial gas, in the process of collapsing from
large scales to form protogalaxies, may also be possible to image through
diffuse recombination line emission, possibly even before stars or BHs are
formed. In this article, I discuss the key physical processes that are expected
to have determined the sizes of the first star-clusters and black holes, and
the prospect of studying these objects by direct detections with JWST and with
other instruments. The direct light emitted by the very first stellar clusters
and intermediate-mass black holes at z>10 will likely fall below JWST's
detection threshold. However, JWST could reveal a decline at the faint-end of
the high-redshift luminosity function, and thereby shed light on radiative and
other feedback effects that operate at these early epochs. JWST will also have
the sensitivity to detect individual SNe from beyond z=10. In a dedicated
survey lasting for several weeks, thousands of SNe could be detected at z>6,
with a redshift distribution extending to the formation of the very first stars
at z>15. Using these SNe as tracers may be the only method to map out the
earliest stages of the cosmic star-formation history. Finally, we point out
that studying the earliest objects at high redshift will also offer a new
window on the primordial power spectrum, on 100 times smaller scales than
probed by current large-scale structure data.Comment: Invited contribution to "Astrophysics in the Next Decade: JWST and
Concurrent Facilities", Astrophysics & Space Science Library, Eds. H.
Thronson, A. Tielens, M. Stiavelli, Springer: Dordrecht (2008
The Voyage of Metals in the Universe from Cosmological to Planetary Scales: the need for a Very High-Resolution, High Throughput Soft X-ray Spectrometer
Metals form an essential part of the Universe at all scales. Without metals we would not exist, and the Cosmos would look completely different. Metals are primarily born through nuclear processes in stars. They leave their cradles through winds or explosions, and then start their journey through space. This can lead them in and out of astronomical objects on all scales, ranging from comets, planets, stars, entire galaxies, groups and clusters of galaxies to the largest structures of the Universe. Their wanderings are fundamental in determining how these objects, and the entire universe, evolve. In addition, their bare presence can be used to trace what these structures look like. The scope of this paper is to highlight the most important open astrophysical problems that will be central in the next decades and for which a deep understanding of the Universe-wandering metals, their physical and kinematical states and their chemical composition represents the only viable solution. The majority of these studies can only be efficiently performed through High Resolution Spectroscopy in the soft X-ray band.Large scale structure and cosmolog