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We present a novel multimodal neural network for classifying astronomical sources in multiband ground-based observations, from optical to near infrared, to separate sources in stars, galaxies and quasars. Our approach combines a convolutional neural network branch for learning morphological features from $r$-band images with an artificial neural network branch for extracting spectral energy distribution (SED) information. Specifically, we have used 9-band optical ($ugri$) and NIR ($ZYHJK_s$) data from the Kilo-Degree Survey (KiDS) Data Release 5. The two branches of the network are concatenated and feed into fully-connected layers for final classification. We train the network on a spectroscopically confirmed sample from the Sloan Digital Sky Survey cross-matched with KiDS. The trained model achieves 98.76\% overall accuracy on an independent testing dataset, with F1 scores exceeding 95\% for each class. Raising the output probability threshold, we obtain higher purity at the cost of a lower completeness. We have also validated the network using external catalogs cross-matched with KiDS, correctly classifying 99.74\% of a pure star sample selected from Gaia parallaxes and proper motions, and 99.74\% of an external galaxy sample from the Galaxy and Mass Assembly survey, adjusted for low-redshift contamination. We apply the trained network to 27,334,751 KiDS DR5 sources with $r \leqslant 23$ mag to generate a new classification catalog. This multimodal neural network successfully leverages both morphological and SED information to enable efficient and robust classification of stars, quasars, and galaxies in large photometric surveys., Comment: 18 pages, 12 figures, 2 tables, Submitted to ApJS

In this work we present a lensing study of Compact Groups (CGs) using data obtained from the high quality Canada-France-Hawaii Telescope Stripe 82 Survey. Using stacking techniques we obtain the average density contrast profile. We analyse the lensing signal dependence on the groups surface brightness and morphological content, for CGs in the redshift range $z = 0.2 - 0.4$. We obtain a larger lensing signal for CGs with higher surface brightness, probably due to their lower contamination by interlopers. Also, we find a strong dependence of the lensing signal on the group concentration parameter, with the most concentrated quintile showing a significant lensing signal, consistent with an isothermal sphere with $\sigma_V =336 \pm 28$ km/s and a NFW profile with $R_{200}=0.60\pm0.05$ $h_{70}^{-1}$Mpc. We also compare lensing results with dynamical estimates finding a good agreement with lensing determinations for CGs with higher surface brightness and higher concentration indexes. On the other hand, CGs that are more contaminated by interlopers show larger dynamical dispersions, since interlopers bias dynamical estimates to larger values, although the lensing signal is weakened., Comment: 11 pages

We set out to quantify the number density of quiescent massive compact galaxies at intermediate redshifts. We determine structural parameters based on i-band imaging using the CFHT equatorial SDSS Stripe 82 (CS82) survey (~170 sq. degrees) taking advantage of an exquisite median seeing of ~0.6''. We select compact massive (M > 5x10^10 M_sun) galaxies within the redshift range of 0.210. We systematically measure a factor of ~5 more compacts at the same redshift than what was previously reported on smaller fields with HST imaging, which are more affected by cosmic variance. This means that the decrease in number density from z ~ 1.5 to z ~ 0.2 might be only of a factor of ~2-5, significantly smaller than what previously reported. This supports progenitor bias as the main contributor to the size evolution. This milder decrease is roughly compatible with the predictions from recent numerical simulations. Only the most extreme compact galaxies, with Reff < 1.5x( M/10^11 M_sun)^0.75 and M > 10^10.7 M_sun, appear to drop in number by a factor of ~20 and hence likely experience a noticeable size evolution., Comment: 15 pages, 16 figures, accepted for publication in MNRAS

We present high signal-to-noise galaxy-galaxy lensing measurements of the BOSS CMASS sample using 250 square degrees of weak lensing data from CFHTLenS and CS82. We compare this signal with predictions from mock catalogs trained to match observables including the stellar mass function and the projected and two dimensional clustering of CMASS. We show that the clustering of CMASS, together with standard models of the galaxy-halo connection, robustly predicts a lensing signal that is 20-40% larger than observed. Detailed tests show that our results are robust to a variety of systematic effects. Lowering the value of $S_{\rm 8}=\sigma_{\rm 8} \sqrt{\Omega_{\rm m}/0.3}$ compared to Planck2015 reconciles the lensing with clustering. However, given the scale of our measurement ($r<10$ $h^{-1}$ Mpc), other effects may also be at play and need to be taken into consideration. We explore the impact of baryon physics, assembly bias, massive neutrinos, and modifications to general relativity on $\Delta\Sigma$ and show that several of these effects may be non-negligible given the precision of our measurement. Disentangling cosmological effects from the details of the galaxy-halo connection, the effects of baryons, and massive neutrinos, is the next challenge facing joint lensing and clustering analyses. This is especially true in the context of large galaxy samples from Baryon Acoustic Oscillation surveys with precise measurements but complex selection functions., Comment: 26 pages. Submitted to MNRAS. Comments welcome

In a galaxy cluster, galaxies are mostly collisionless particles in recent epoches. They resemble collisionless cold dark matter particles in some way. Therefore, the spatial distributions of dark matter and cluster galaxies might be expected to possess similar features in the gravitational potential of a cluster. Here we use the galaxy distribution in cluster Cl0024+17 to probe for the ringlike dark matter structure recently discovered by means of strong and weak lensing observations. The galaxies are taken from the catalog of Czoske et al., which contains 650 objects with measured redshifts, of which ~300 galaxies have redshifts in the range 0.37