a deep imaging survey of massive galaxies and their surroundings
HiPS images for the all MATLAS fields and bands have been produced and made available to the community through the Aladin Lite and Aladin desktop facilities, with all the associated services of the CDS.
Many thanks to Thomas Boch and the CDS team at Strasbourg astronomical observatory !
Robustness to transformation is desirable in many computer vision tasks, given that input data often exhibits pose variance within classes. While translation invariance and equivariance is a documented phenomenon of CNNs, sensitivity to other transformations is typically encouraged through data augmentation. We investigate the modulation of complex valued convolutional weights with learned Gabor filters to enable orientation robustness. With Gabor modulation, the designed network is able to generate orientation dependent features free of interpolation with a single set of rotation-governing parameters. Moreover, by learning rotation parameters alongside traditional convolutional weights, the representation space is not constrained and may adapt to the exact input transformation. We present Learnable Convolutional Gabor Networks (LCGNs), that are parameter-efficient and offer increased model complexity while keeping backpropagation simple. We demonstrate that learned Gabor modulation utilising an end-to-end complex architecture enables rotation invariance and equivariance on MNIST and a new dataset of simulated images of galactic cirri.
Richards et al., 2020, Arxiv
Deep imaging, that is imaging capable of capturing very low surface brightness extended objects, is a quickly growing field of extragalactic astronomy. Not only can new types of faint objects be discovered, but deep images of bright galaxies are very valuable, too, since they reveal faint signs of past galaxy collisions, the tidal features. Such “archeological” record can be exploited for investigating how galaxies formed. In the MATLAS survey, we obtained extremely deep images of 177 nearby massive elliptical and lenticular galaxies using the 3.5m Canada-France-Hawaii Telescope.
Continue reading “The MATLAS survey of faint outskirts of bright galaxies”
Accounting for the morphology is an essential constraint for the theory of galaxy formation. The low-surface brightness regions of galaxies host multiple morphological features that any realistic model should consider; however they are still not fully explored because of observational difficulties. Here we present the results of our visual inspections of very deep images of a complete large volume-limited sample of 177 nearby massive early-type galaxies (ETGs) from the MATLAS survey.
Continue reading “Census and classification of low-surface-brightness structures in nearby early-type galaxies from the MATLAS survey”
Stellar shells around galaxies could provide precious insights into their assembly history. However, their formation mechanism remains poorly empirically constrained, regarding in particular the type of galaxy collisions at their origin. We present MUSE at VLT data of the most prominent outer shell of NGC 474, to constrain its formation history. The stellar shell spectrum is clearly detected, with a signal-to-noise ratio of ∼65 pix-1. We used a full spectral fitting method to determine the line-of-sight velocity and the age and metallicity of the shell and associated point-like sources within the MUSE field of view.
Continue reading “Revealing the formation mechanism of the shell galaxy NGC474 with MUSE”
The MATLAS deep imaging survey has uncovered a plethora of dwarf galaxies in the low density environment it has mapped. A fraction of them are unusually extended and have a low-surface brightness. Among these so-called ultra-diffuse galaxies, a few seem to host an excess of globular clusters. With the integral-field unit spectrograph MUSE we have observed one of these galaxies – MATLAS J15052031+0148447 (MATLAS-2019) – located towards the nearby group NGC 5846 and measured its systemic velocity, age, and metallicity, and that of its globular clusters candidates.
Continue reading “A spectroscopic study of MATLAS-2019 with MUSE: an ultra-diffuse galaxy with an excess of old globular clusters”
We present interferometric HI observations of six double-disc stellar counterrotator (“2σ”) galaxies from the ATLAS3D sample.
Continue reading “Atomic Hydrogen Clues to the Formation of Counterrotating Stellar Discs (associated paper)”
Full sample of 177 early type galaxies galaxies from the Atlas3D sample, with deep g and r images (u and i bands available for a sub-sample). The survey is presented in Bilek et al., 2020. Data are complemented by a sample of 55 late type galaxies from the Atlas3D parent sample located in the field of the ETGs.
Fully processed images in jpeg format, including true color images and surface brightness maps, are made publicly available though a dedicated navigation tool and image browsing facilities, such as band switching, color and contrast changes, catalog superimposition or image profile cuts. Image browsing relies on developments made by the VisiOmatic project using the IIPImage web client developed
Data can be accessed from here