3,161 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
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
Cosmology with intensity mapping techniques using atomic and molecular lines
We present a systematic study of the intensity mapping technique using
updated models for the different emission lines from galaxies and identify
which ones are more promising for cosmological studies of the post reionization
epoch. We consider the emission of , , H,
optical and infrared oxygen lines, nitrogen lines, CII and the CO rotational
lines. We then identify that , , OII, CII and
the lowest rotational CO lines are the best candidates to be used as IM probes.
These lines form a complementary set of probes of the galaxies emission
spectra. We then use reasonable experimental setups from current, planned or
proposed experiments to access the detectability of the power spectrum of each
emission line. Intensity mapping of emission from to 3
will be possible in the near future with HETDEX, while far-infrared lines
require new dedicated experiments. We also show that the proposed SPHEREx
satellite can use OII and IM to study the large-scale
distribution of matter in intermediate redshifts of 1 to 4. We found that
submilimeter experiments with bolometers can have similar performances at
intermediate redshifts using CII and CO(3-2).Comment: 18 pages, 21 figures, 5 tables, published in MNRAS, typos correcte
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
Prospects for detecting CII emission during the Epoch of Reionization
We produce simulations of emission of the atomic CII line in large sky fields
in order to determine the current prospects for mapping this line during the
high redshift Epoch of Reionization. We estimate the CII line intensity,
redshift evolution and spatial fluctuations using observational relations
between CII emission and the SFR in a galaxy for the frequency range of 200 GHz
to 300 GHz. We obtained a frequency averaged intensity of CII emission of in the redshift range
. Observations of CII emission in this frequency
range will suffer contamination from emission lines at lower redshifts, in
particular from the CO rotation lines. For the relevant frequency range we
estimated the CO contamination (originated in emission from galaxies at ), using simulations, to be and independently confirmed the result based in observational
relations. We generated maps as a function of angle and frequency using
detailed simulations of the CII and CO emission across several redshifts in
order to properly take into account the observational pipeline and light cone
effects. In order to reduce the foreground contamination we found that we
should mask galaxies below redshifts with a CO flux in one of the
CO(J:2-1) to CO(J:6-5) lines higher than
or a AB magnitude lower than . We estimate that the
additional continuum contamination is of the order of . It is also considered the possibility of cross correlating
foreground lines with galaxies in order to probe the intensity of the
foregrounds.Comment: 19 pages, 14 figure
Probing Reionization with Intensity Mapping of Molecular and Fine Structure Lines
We propose observations of the molecular gas distribution during the era of reionization. At z~ 6-8, the ^(12)CO(J = 1-0) line intensity results in a mean brightness temperature of about 0.5 μK with an rms fluctuation of 0.1 μK at 1-10 Mpc spatial scales, corresponding to 30 arcminute angular scales. This intensity fluctuations can be mapped with an interferometer, similar to existing and planned 21 cm background experiments, but operating at ~12-17 GHz. We discuss the feasibility of detecting the cross-correlation between H I and CO molecular gas since such a cross-correlation has the advantage that it will be independent of systematics and most foregrounds in each of the 21 cm and CO(1-0) line experiments. Additional instruments tuned to higher-order transitions of the CO molecule or an instrument operating with high spectral resolution at millimeter wavelengths targeting 158 μm C II could further improve the reionization studies with molecular gas. The combined 21 cm and CO line observations has the potential to establish the relative distribution of gas in the intergalactic medium and molecular gas that are clumped in individual first-light galaxies that are closely connected to the formation of massive stars in these galaxies
Suspended-core fibers for sensing applications
A brief review on suspended-core fibers for sensing applications is presented. A historical overview over the previous ten years about this special designed microstructure optical fiber is described. This fiber presents attractive optical properties for chemical/biological or gas measurement, but it can be further explored for alternative sensing solutions, namely, in-fiber interferometers based on the suspended-core or suspended-multi-core fiber, for physical parameter monitoring.info:eu-repo/semantics/publishedVersio
A Foreground Masking Strategy for [CII] Intensity Mapping Experiments Using Galaxies Selected by Stellar Mass and Redshift
Intensity mapping provides a unique means to probe the epoch of reionization
(EoR), when the neutral intergalactic medium was ionized by the energetic
photons emitted from the first galaxies. The [CII] 158m fine-structure
line is typically one of the brightest emission lines of star-forming galaxies
and thus a promising tracer of the global EoR star-formation activity. However,
[CII] intensity maps at are contaminated by
interloping CO rotational line emission () from
lower-redshift galaxies. Here we present a strategy to remove the foreground
contamination in upcoming [CII] intensity mapping experiments, guided by a
model of CO emission from foreground galaxies. The model is based on empirical
measurements of the mean and scatter of the total infrared luminosities of
galaxies at
selected in -band from the COSMOS/UltraVISTA survey, which can be converted
to CO line strengths. For a mock field of the Tomographic Ionized-carbon
Mapping Experiment (TIME), we find that masking out the "voxels"
(spectral-spatial elements) containing foreground galaxies identified using an
optimized CO flux threshold results in a -dependent criterion (or ) at and makes a [CII]/CO power ratio of at
/Mpc achievable, at the cost of a moderate loss of total
survey volume.Comment: 14 figures, 4 tables, re-submitted to ApJ after addressing reviewer's
comments. Comments welcom
The trans-Saharan slave trade - clues from interpolation analyses and high-resolution characterization of mitochondrial DNA lineages
<p>Abstract</p> <p>Background</p> <p>A proportion of 1/4 to 1/2 of North African female pool is made of typical sub-Saharan lineages, in higher frequencies as geographic proximity to sub-Saharan Africa increases. The Sahara was a strong geographical barrier against gene flow, at least since 5,000 years ago, when desertification affected a larger region, but the Arab trans-Saharan slave trade could have facilitate enormously this migration of lineages. Till now, the genetic consequences of these forced trans-Saharan movements of people have not been ascertained.</p> <p>Results</p> <p>The distribution of the main L haplogroups in North Africa clearly reflects the known trans-Saharan slave routes: West is dominated by L1b, L2b, L2c, L2d, L3b and L3d; the Center by L3e and some L3f and L3w; the East by L0a, L3h, L3i, L3x and, in common with the Center, L3f and L3w; while, L2a is almost everywhere. Ages for the haplogroups observed in both sides of the Saharan desert testify the recent origin (holocenic) of these haplogroups in sub-Saharan Africa, claiming a recent introduction in North Africa, further strengthened by the no detection of local expansions.</p> <p>Conclusions</p> <p>The interpolation analyses and complete sequencing of present mtDNA sub-Saharan lineages observed in North Africa support the genetic impact of recent trans-Saharan migrations, namely the slave trade initiated by the Arab conquest of North Africa in the seventh century. Sub-Saharan people did not leave traces in the North African maternal gene pool for the time of its settlement, some 40,000 years ago.</p
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