Context.
The magnification bias on the submillimetre galaxies (SMGs) is a gravitational lensing effect, where the SMGs are used as background lensed galaxies. This effect can be used to investigate ...the mass density profiles of different types of foreground lenses.
Aims.
In this work, we want to exploit the magnification bias of the SMGs using two different foreground samples, quasi-stellar objects (QSOs) and galaxies. Our aim is to study and compare their mass density profiles and estimate their masses and concentrations.
Methods.
The background SMG sample consists of objects observed by
Herschel
with 1.2 <
z
< 4.0 (mean redshift at ∼2.2). The foreground samples are QSOs with spectroscopic redshifts 0.2 <
z
< 1.0 (mean redshift at ∼0.7) and massive galaxies with also spectroscopic redshifts 0.2 <
z
< 1.0 (mean redshift at ∼0.3). The cross-correlation measurements are estimated with the Davis-Peebles estimator by stacking the SMG–QSO and SMG–galaxy pairs for the two analysed cases, respectively. The advantage of such an approach is that it allows us to study the mass density profile over a wide range of angular scales, from ∼2 to ∼250 arcsec, including the inner part of the dark-matter halo (≲100 kpc). Moreover, the analysis is carried out by combining two of the most common theoretical mass density profiles in order to fit the cross-correlation measurements.
Results.
The measurements are correctly fitted after splitting the available angular scales into an inner and an outer part using two independent mass density profiles, one for each region. In particular, for the QSOs, we obtain masses of log
10
(
M
/
M
⊙
) = 13.51 ± 0.04 and of log
10
(
M
/
M
⊙
) = 13.44 ± 0.17 for the inner and outer parts, respectively. The estimated masses for the galaxy sample are log
10
(
M
/
M
⊙
) = 13.32 ± 0.08 and log
10
(
M
/
M
⊙
) = 12.78 ± 0.21 for the inner and outer parts, respectively. The concentrations for the inner part are much higher than those for the outer region for both samples:
C
= 6.85 ± 0.34 (inner) and
C
= 0.36 ± 0.18 (outer) for the QSOs and
C
= 8.23 ± 0.77 (inner) and
C
= 1.21 ± 1.01 (outer) for the galaxies.
Conclusions.
In both samples, the inner part has an excess in the mass density profile with respect to the outer part for both QSOs and galaxy samples. We obtain similar values for the central mass with both samples, and they are also in agreement with those of galaxy clusters results. However, the estimated masses for the outer region and the concentrations of the inner region both vary with lens sample. We believe this to be related to the probability of galactic interactions and/or the different evolutionary stages.
We use the Herschel-ATLAS survey to conduct the first large-scale statistical study of the submillimetre properties of optically selected galaxies. Using ∼80 000 r-band selected galaxies from 126 ...deg2 of the GAMA survey, we stack into submillimetre imaging at 250, 350 and 500 μ m to gain unprecedented statistics on the dust emission from galaxies at z < 0.35. We find that low-redshift galaxies account for 5 per cent of the cosmic 250-μm background (4 per cent at 350 μ m; 3 per cent at 500 μ m), of which approximately 60 per cent comes from 'blue' and 20 per cent from 'red' galaxies (rest-frame g−r). We compare the dust properties of different galaxy populations by dividing the sample into bins of optical luminosity, stellar mass, colour and redshift. In blue galaxies we find that dust temperature and luminosity correlate strongly with stellar mass at a fixed redshift, but red galaxies do not follow these correlations and overall have lower luminosities and temperatures. We make reasonable assumptions to account for the contaminating flux from lensing by red-sequence galaxies and conclude that galaxies with different optical colours have fundamentally different dust emission properties. Results indicate that while blue galaxies are more luminous than red galaxies due to higher temperatures, the dust masses of the two samples are relatively similar. Dust mass is shown to correlate with stellar mass, although the dust-to-stellar mass ratio is much higher for low stellar mass galaxies, consistent with the lowest mass galaxies having the highest specific star formation rates. We stack the 250 μ m-to-NUV luminosity ratio, finding results consistent with greater obscuration of star formation at lower stellar mass and higher redshift. Submillimetre luminosities and dust masses of all galaxies are shown to evolve strongly with redshift, indicating a fall in the amount of obscured star formation in ordinary galaxies over the last four billion years.
Context. Magnification bias, an observational effect of gravitational lensing in the weak regime, allows the cosmological model to be tested through angular correlations of sources at different ...redshifts. This effect has been observed in various contexts, particularly with sub-millimetre galaxies (SMGs), offering valuable astrophysical and cosmological insights. Aims. The study aims to investigate the magnification bias effect exerted by galaxy clusters on SMGs and its implications for astrophysical and cosmological parameters within the Λ-CDM model. Methods. Magnification bias was explored by quantifying the cross-correlation function, which we then utilised to derive constraints on cosmological and astrophysical parameters with a Markov chain Monte Carlo algorithm. Two distinct galaxy cluster samples were used to assess result robustness and understand the influence of sample characteristics. Results. Cluster samples show higher cross-correlation values than galaxies, with an excess at larger scales suggesting contributions from additional large-scale structures. The parameters obtained, while consistent with those of galaxies, are less constrained due to broader redshift distributions and limited cluster statistics. Results align with weak lensing studies, hinting at slightly lower σ 8 and Ω m values than Planck ’s cosmic microwave background data, emphasising the need for enhanced precision and alternative low-redshift universe tests. Conclusions. While this method yields constraints that are compatible with the Λ-CDM model, its limitations include broader redshift distributions and a limited number of lenses, resulting in less constrained parameters compared to previous galaxy studies. Nonetheless, our study underscores the potential of using galaxy clusters as lenses for magnification bias studies, capitalising on their elevated masses and thus providing a promising avenue to test current cosmology theories. Further progress can be made by expanding the lens sample size.
ALMA photometry of extragalactic radio sources Bonato, M; Liuzzo, E; Herranz, D ...
Monthly Notices of the Royal Astronomical Society,
05/2019, Letnik:
485, Številka:
1
Journal Article
The Large Area Telescope on board the Fermi Gamma-ray Space Telescope detected a strong γ-ray flare on 2011 May 15 from a source identified as 4C +49.22, a flat spectrum radio quasar (FSRQ) also ...known as S4 1150+49. This blazar, characterized by a prominent radio–optical–X-ray jet, was in a low γ-ray activity state during the first years of Fermi observations. Simultaneous observations during the quiescent, outburst and post-flare γ-ray states were obtained by Swift, Planck and optical–IR–radio telescopes (Instituto Nacional de Astrofísica, Óptica y Electrónica, Catalina Sky Survey, Very Long Baseline Array VLBA, Metsähovi). The flare is observed from microwave to X-ray bands with correlated variability and the Fermi, Swift and Planck data for this FSRQ show some features more typical of BL Lac objects, like the synchrotron peak in the optical band that outshines the thermal blue-bump emission, and the X-ray spectral softening. Multi-epoch VLBA observations show the ejection of a new component close in time with the GeV γ-ray flare. The radio-to-γ-ray spectral energy distribution is modelled and fitted successfully for the outburst and the post-flare epochs using either a single flaring blob with two emission processes (synchrotron self-Compton (SSC), and external-radiation Compton), and a two-zone model with SSC-only mechanism.
Context.
As recently demonstrated, high-
z
submillimetre galaxies (SMGs) are the perfect background sample for tracing the mass density profiles of galaxies and clusters (baryonic and dark matter) ...and their time-evolution through gravitational lensing. Their magnification bias, a weak gravitational lensing effect, is a powerful tool for constraining the free parameters of a halo occupation distribution (HOD) model and potentially also some of the main cosmological parameters.
Aims.
The aim of this work is to test the capability of the magnification bias produced on high-
z
SMGs as a cosmological probe. We exploit cross-correlation data to constrain not only astrophysical parameters (
M
min
,
M
1
, and
α
), but also some of the cosmological ones (Ω
m
,
σ
8
, and
H
0
) for this proof of concept.
Methods.
The measured cross-correlation function between a foreground sample of GAMA galaxies with spectroscopic redshifts in the range 0.2 <
z
< 0.8 and a background sample of H-ATLAS galaxies with photometric redshifts > 1.2 is modelled using the traditional halo model description that depends on HOD and cosmological parameters. These parameters are then estimated by performing a Markov chain Monte Carlo analysis using different sets of priors to test the robustness of the results and to study the performance of this novel observable with the current set of data.
Results.
With our current results, Ω
m
and
H
0
cannot be well constrained. However, we can set a lower limit of > 0.24 at 95% confidence level (CL) on Ω
m
and we see a slight trend towards
H
0
> 70 values. For our constraints on
σ
8
we obtain only a tentative peak around 0.75, but an interesting upper limit of
σ
8
≲ 1 at 95% CL. We also study the possibility to derive better constraints by imposing more restrictive priors on the astrophysical parameters.
Context.
Constraining the polarisation properties of extragalactic point sources is a relevant task not only because they are one of the main contaminants for primordial cosmic microwave background ...B-mode detection if the tensor-to-scalar ratio is lower than
r
= 0.001, but also for a better understanding of the properties of radio-loud active galactic nuclei.
Aims.
We develop and train a machine learning model based on a convolutional neural network to learn how to estimate the polarisation flux density and angle of point sources embedded in cosmic microwave background images knowing only their positions.
Methods.
To train the neural network, we used realistic simulations of patches of 32 × 32 pixels in area at the 217 GHz
Planck
channel with injected point sources at their centres. The patches also contain a realistic background composed of the cosmic microwave background signal, the Galactic thermal dust, and instrumental noise. We split our analysis into three parts: firstly, we studied the comparison between true and estimated polarisation flux densities for
P, Q
, and
U
simulations. Secondly, we analysed the comparison between true and estimated polarisation angles. Finally, we studied the performance of our model with the 217 GHz
Planck
map and compared our results against the detected sources of the Second
Planck
Catalogue of Compact Sources (PCCS2).
Results.
We find that our model can be used to reliably constrain the polarisation flux density of sources above the 80 mJy level. For this limit, we obtain relative errors of lower than 30% in most of the flux density levels. Training the same network with
Q
and
U
maps, the reliability limit is above ±250 mJy when determining the polarisation angle of both
Q
and
U
sources. Above that cut, the network can constrain angles with a 1
σ
uncertainty of ±29° and ±32° for
Q
and
U
sources, respectively. We test this neural network against real data from the 217 GHz
Planck
channel, obtaining similar results to the PCCS2 for some sources; although we also find discrepancies in the 300–400mJy flux density range with respect to the
Planck
catalogue.
Conclusions.
Based on these results, our model appears to be a promising tool for estimating the polarisation flux densities and angles of point sources above 80 mJy in any catalogue with very small computational time requirements.
ABSTRACT
We have carried out Hubble Space Telescope (HST) snapshot observations at 1.1 μm of 281 candidate strongly lensed galaxies identified in the wide-area extragalactic surveys conducted with ...the Herschel Space Observatory. Our candidates comprise systems with flux densities at $500\, \mu$m, S500 ≥ 80 mJy. We model and subtract the surface brightness distribution for 130 systems, where we identify a candidate for the foreground lens candidate. After combining visual inspection, archival high-resolution observations, and lens subtraction, we divide the systems into different classes according to their lensing likelihood. We confirm 65 systems to be lensed. Of these, 30 are new discoveries. We successfully perform lens modelling and source reconstruction on 23 systems, where the foreground lenses are isolated galaxies and the background sources are detected in the HST images. All the systems are successfully modelled as a singular isothermal ellipsoid. The Einstein radii of the lenses and the magnifications of the background sources are consistent with previous studies. However, the background source circularized radii (between 0.34 and 1.30 kpc) are ∼3 times smaller than the ones measured in the sub-millimetre/millimetre for a similarly selected and partially overlapping sample. We compare our lenses with those in the Sloan Lens Advanced Camera for Surveys (ACS) Survey confirming that our lens-independent selection is more effective at picking up fainter and diffuse galaxies and group lenses. This sample represents the first step towards characterizing the near-infrared properties and stellar masses of the gravitationally lensed dusty star-forming galaxies.
Context.
High-z submillimetre galaxies can be used as a background sample for gravitational lensing studies thanks to their magnification bias. In particular, the magnification bias can be exploited ...in order to constrain the free parameters of a halo occupation distribution (HOD) model and some of the main cosmological parameters. A pseudo-tomographic analysis shows that the tomographic approach should improve the parameter estimation.
Aims.
In this work the magnification bias has been evaluated as cosmological tool in a tomographic set-up. The cross-correlation function (CCF) data have been used to jointly constrain the astrophysical parameters
M
min
,
M
1
, and
α
in each of the selected redshift bins as well as the cosmological parameters Ω
M
,
σ
8
, and
H
0
for the lambda cold dark matter (ΛCDM) model. Moreover, we explore the possible time evolution of the dark energy density by also introducing the
ω
0
,
ω
a
parameters in the joint analysis (
ω
0
CDM and
ω
0
ω
a
CDM).
Methods.
The CCF was measured between a foreground spectroscopic sample of Galaxy And Mass Assembly galaxies and a background sample of
Herschel
Astrophysical Terahertz Large Area Survey (H-ATLAS) galaxies. The foreground sample was divided into four redshift bins (0.1–0.2, 0.2–0.3, 0.3–0.5, and 0.5–0.8) and the sample of H-ATLAS galaxies has photometric redshifts > 1.2. The CCF was modelled using a halo model description that depends on HOD and cosmological parameters. Then a Markov chain Monte Carlo method was used to estimate the parameters for different cases.
Results.
For the ΛCDM model the analysis yields a maximum posterior value at 0.26 with 0.17, 0.41 68% C.I. for Ω
M
and at 0.87 with 0.75, 1 68% C.I. for
σ
8
. With our current results
H
0
is not yet constrained. With a more general
ω
0
CDM model, the constraints on Ω
M
and
σ
8
are similar, but we found a maximum posterior value for
ω
0
at −1 with − 1.56, −0.47 68% C.I. In the
ω
0
ω
a
CDM model, the results are −1.09 with − 1.72, −0.66 68% C.I. for
ω
0
and −0.19 with − 1.88, 1.48 68% C.I. for
ω
a
.
Conclusions.
The results on
M
min
show a trend towards higher values at higher redshift confirming recent findings. The tomographic analysis presented in this work improves the constraints in the
σ
8
− Ω
M
plane with respect to previous findings exploiting the magnification bias and it confirms that magnification bias results do not show the degeneracy found with cosmic shear measurements. Moreover, related to dark energy, we found a trend of higher
ω
0
values for lower
H
0
values.
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