31 research outputs found
Filament Hunting: Integrated HI 21cm Emission From Filaments Inferred by Galaxy Surveys
Large scale filaments, with lengths that can reach tens of Mpc, are the most
prominent features in the cosmic web. These filaments have only been observed
indirectly through the positions of galaxies in large galaxy surveys or through
absorption features in the spectra of high redshift sources. In this study we
propose to go one step further and directly detect intergalactic medium
filaments through their emission in the HI 21cm line. We make use of high
resolution cosmological simulations to estimate the intensity of this emission
in low redshift filaments and use it to make predictions for the direct
detectability of specific filaments previously inferred from galaxy surveys, in
particular the Sloan Digital Sky Survey. Given the expected signal of these
filaments our study shows that HI emission from large filaments can be observed
by current and next generation radio telescopes. We estimate that gas in
filaments of length 15 Mpc with relatively small
inclinations to the line of sight () can be observed in
hours with telescopes such as GMRT or EVLA, potentially providing
large improvements over our knowledge of the astrophysical properties of these
filaments. Due to their large field of view and sufficiently long integration
times, upcoming HI surveys with the Apertif and ASKAP instruments will be able
to detect large filaments independently of their orientation and curvature.
Furthermore, our estimates indicate that a more powerful future radio telescope
like SKA-2 can be used to map most of these filaments, which will allow them to
be used as a strong cosmological probe.Comment: 16 pages, 11 figures, Accepted for publication in MNRA
Large-scale filaments and the intergalactic medium
Wanneer we de verdeling van materie in het huidige universum op de grootste schalen bekijken, zien we een ingewikkeld patroon van knooppunten, aan elkaar verbonden door draadvormige filamenten, het kosmische web. De meeste sterrenstelsels worden gevormd in de filamenten. Al het gas buiten de sterrenstelsels wordt het intergalactische medium genoemd (IGM). Gas in het IGM bestaat voornamelijk uit waterstof en helium. Het IGM in de filamenten kan de evolutie en formatie van de sterrenstelsels beïnvloeden. Om de formatieprocessen van sterren en sterrenstelsels beter te begrijpen is het daarom belangrijk om de eigenschappen van het gas te bestuderen. Door de hoeveelheid van het neutrale gas te meten wordt het mogelijk om de temperatuur en de ionisatietoestand in het IGM te bepalen, maar het meetbare signaal van dit gas is erg zwak. Het doel van dit proefschrift is om te onderzoeken of huidige en aankomende instrumenten een dergelijke meting toch kunnen uitvoeren. Hiervoor zijn simulaties gebruikt om het signaal van het IGM in filamenten te voorspellen. Vervolgens worden de benodigdheden bepaald om ultraviolette straling van het kosmische web in kaart te brengen met een ruimtetelescoop. Bovendien wordt voor radiostraling van het IGM een methode uitgewerkt waarbij eerst de positie van een filament wordt voorspeld met behulp van de verdeling van sterrenstelsels om vervolgens een geïntegreerd radiosignaal te kunnen bepalen door het filament te volgen. Dit werk toont aan dat een aantal huidige en toekomstige radiotelescopen gevoelig genoeg zijn om dit geintegreerde signaal te detecteren
Tomographic Intensity Mapping versus Galaxy Surveys: Observing the Universe in H-alpha emission with new generation instruments
The H-alpha line emission is an important probe for a number of fundamental
quantities in galaxies, including their number density, star formation rate
(SFR) and overall gas content. A new generation of low-resolution intensity
mapping probes, e.g. SPHEREx and CDIM, will observe galaxies in H-alpha
emission over a large fraction of the sky from the local Universe till a
redshift of z ~ 6 to 10, respectively. This will also be the target line for
observations by the high-resolution Euclid and WFIRST instruments in the z ~
0.7 - 2 redshift range. In this paper, we estimate the intensity and power
spectra of the H-alpha line in the z ~ 0 - 5 redshift range using observed line
luminosity functions (LFs), when possible, and simulations, otherwise. We
estimate the significance of our predictions by accounting for the modelling
uncertainties (e.g. SFR, extinction, etc.) and observational contamination. We
find that Intensity Mapping (IM) surveys can make a statistical detection of
the full H-alpha emission between z ~ 0.8 - 5. Moreover, we find that the
high-frequency resolution and the sensitivity of the planned CDIM surveys allow
for the separation of H-alpha emission from several interloping lines. We
explore ways to use the combination of these line intensities to probe galaxy
properties. As expected, our study indicates that galaxy surveys will only
detect bright galaxies that contribute up to a few percent of the overall
H-alpha intensity. However, these surveys will provide important constraints on
the high end of the H-alpha LF and put strong constraints on the AGN LF.Comment: Submitted to MNRA
Erratum:Filament Hunting: Integrated HI 21cm Emission From Filaments Inferred by Galaxy Surveys [MNRAS, (2019)] DOI: 10.1093/mnras/stx509
This is an erratum to the paper' Filament Hunting: Integrated HI 21cm Emission From Filaments Inferred by Galaxy Surveys' that was published in MNRAS, 468, 857. Due to the use of an incorrect equation to calculate the thermal noise of an observation, the noise was underestimated in the paper, affecting some of our conclusions
Cost-effectiveness of blended vs. face-to-face cognitive behavioural therapy for severe anxiety disorders: study protocol of a randomized controlled trial
Background: Anxiety disorders are among the most prevalent psychiatric conditions, and are associated with poor
quality of life and substantial economic burden. Cognitive behavioural therapy is an effective treatment to reduce
anxiety symptoms, but is also costly and labour intensive. Cost-effectiveness could possibly be improved by delivering
cognitive behavioural therapy in a blended format, where face-to-face sessions are partially replaced by online sessions.
The aim of this trial is to determine the cost-effectiveness of blended cognitive behavioural therapy for adults with
anxiety disorders, i.e. panic disorder, social phobia or generalized anxiety disorder, in specialized mental health care
settings compared to face-to-face cognitive behavioural therapy. In this paper, we present the study protocol. It is
hypothesized that blended cognitive behavioural therapy for anxiety disorders is clinically as effective as face-to-face
cognitive behavioural therapy, but that intervention costs may be reduced. We thus hypothesize that blended
cognitive behavioural therapy is more cost-effective than face-to-face cognitive behavioural therapy.
Methods/design: In a randomised controlled equivalence trial 156 patients will be included (n = 78 in blended
cognitive behavioural therapy, n = 78 in face-to-face cognitive behavioural therapy) based on a power of 0.80,
calculated by using a formula to estimate the power of a cost-effectiveness analysis:
Measurements will take place at baseline, midway treatment (7 weeks), immediately after treatment (15 weeks)
and 12-month follow-up. At baseline a diagnostic interview will be administered. Primary clinical outcomes
are changes in anxiety symptom severity as measured with the Beck Anxiety Inventory. An incremental cost-effectiveness
ratio will be calculated to obtain the costs per quality-adjusted life years (QALYs) measured by the
EQ-5D (5-level version). Health-economic outcomes will be explored from a societal and health care perspective.
Discussion: This trial will be one of the first to provide information on the cost-effectiveness of blended
cognitive behavioural therapy for anxiety disorders in routine specialized mental health care settings, both from
a societal and a health care perspective
Field testing for toxic algae with a microarray: initial results from the MIDTAL project
One of the key tasks in MIDTAL (MIcroarrays for the Detection of Toxic ALgae) is to demonstrate
the applicability of microarrays to monitor harmful algae across a broad range of ecological niches
and toxic species responsible for harmful algal events. Water samples are collected from a series of
sites used in national phytoplankton and biotoxin monitoring across Europe. The samples are filtered;
rRNA is extracted, labelled with a fluorescent dye and applied to a microarray chip. The signal
intensity from >120 probes previously spotted on the chip is measured and analysed. Preliminary
results comparing microarray signal intensities with actual field counts are presented.Versión del edito
Radial decoupling of small and large dust grains in the transitional disk RX J1615.3-3255
We present H-band (1.6 {\mu}m) scattered light observations of the
transitional disk RX J1615.3-3255, located in the ~1 Myr old Lupus association.
From a polarized intensity image, taken with the HiCIAO instrument of the
Subaru Telescope, we deduce the position angle and the inclination angle of the
disk. The disk is found to extend out to 68 12 AU in scattered light and
no clear structure is observed. Our inner working angle of 24 AU does not allow
us to detect a central decrease in intensity similar to that seen at 30 AU in
the 880 {\mu}m continuum observations. We compare the observations with
multiple disk models based on the Spectral Energy Distribution (SED) and submm
interferometry and find that an inner rim of the outer disk at 30 AU containing
small silicate grains produces a polarized intensity signal which is an order
of magnitude larger than observed. We show that a model in which the small dust
grains extend smoothly into the cavity found for large grains is closer to the
actual H-band observations. A comparison of models with different dust size
distributions suggests that the dust in the disk might have undergone
significant processing compared to the interstellar medium.Comment: 8 pages, 7 figures, 4 tables. Accepted for publication in A&