Searcharxiv⌕ Search

arXiv subjects

Francine Marleau

Publications and source records attributed to Francine Marleau.

13 recordsLinked to original sources
arXiv2026

Generating the wide sequence of Diffuse Galaxies with de Broglie waves of Dark Matter

Extensive Euclid satellite imaging at low surface brightness has revealed that most nearby galaxies are diffuse-looking spheroids, where the stellar radius increases monotonically over three decades in luminosity. We argue this Diffuse Galaxy sequence results from internal stellar diffusion by Wave Dark Matter ($ψ$DM), as wave energy is transferred to star orbits over time. In particular, the soliton random motion scatters central stars onto radial orbits that become enhanced with each passage through the centre, slowly "puffing up" the stellar profile. Heating is greater within massive galaxies as $ψ$DM fluctuations are stronger and more frequent, reproducing the Diffuse Galaxy sequence and also accounts for the rising velocity dispersion along the sequence, from Ultra-Faint to Dwarf Spheroidal and Ultra Diffuse galaxies, favouring a light boson, $m_ψ=2.88^{+0.14}_{-0.13}\times10^{-22}$eV. Winding back this diffusion, we predict the stellar content of Diffuse Galaxies, including globular clusters, formed near the centre, as anticipated by $ψ$DM simulations, where gas cools efficiently within the dense soliton. This predicted $ψ$DM evolution from compact beginnings towards diffuse-looking spheroidal galaxies today can now be fully charted from JWST to Euclid.

astro-ph.GA↗
arXiv2025

Unlocking the physics of dwarf galaxies in the 2040s: The case for a next-generation wide-field spectroscopic facility with fibres and IFUs

Dwarf galaxies ($M_{\star} \lesssim 10^{9} M_{\odot}$) are the most numerous galaxies in the Universe and critical probes of dark matter, baryonic feedback, and galaxy formation. Despite significant progress from wide-field imaging surveys, the majority of dwarf candidates beyond the Local Group will lack spectroscopic follow-up, leaving fundamental questions about their internal kinematics, stellar populations, chemical enrichment, and dark matter content unresolved. Existing and planned facilities cannot efficiently provide the necessary spectroscopy for low-surface-brightness dwarfs over wide areas. We advocate for a dedicated large-aperture ($\geq 20$ m), wide-field, highly multiplexed spectroscopic facility with deployable or monolithic IFUs, capable of high signal-to-noise observations down to $I_{\rm E} \gtrsim 22-23$ mag. Such a facility would enable transformative studies of dark matter cores, baryonic feedback, tidal interactions, environmental effects, and stellar populations, extending the spectroscopic exploration of low-mass galaxies to $z \sim 1.5$, and providing decisive tests of $Λ$CDM and alternative dark matter models. Beyond dwarfs, this capability would impact galaxy evolution, strong and weak lensing studies, and cosmology, ensuring that imaging data from the 2030s and 2040s can be fully exploited.

astro-ph.IM↗
arXiv2025

Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: A Low Surface Brightness Science Case

The Extragalactic Low Surface Brightness (LSB, $μ_V\gtrsim 27$ mag/arcsec$^2$) Universe represents a crucial, yet largely unseen, frontier in modern astrophysics. This faint realm holds the keys to completing our understanding of galaxy evolution, hierarchical assembly, and even the fundamental nature of dark matter. Our current theoretical models are inherently incomplete, largely mirroring the properties of the brightest, most easily observed objects. To overcome this critical bias and unlock the secrets of this realm, a transformative leap in observational capability is required. A 30 to 40m class telescope, leveraging unprecedented sensitivity and spatial resolution, especially with adaptive optics, is the essential tool to fundamentally probe these faint, low-density stellar regimes. This white paper details the transformative LSB science that such a facility, strategically positioned in the Northern Hemisphere (NH) to access crucial nearby structures and rich environments, can achieve.

astro-ph.IM↗
arXiv2025

Low Surface Brightness structures from annotated deep CFHT images: effects of the host galaxy's properties and environment

Hierarchical galactic evolution models predict that mergers drive galaxy growth, producing low surface brightness (LSB) tidal features that trace galaxies' late assembly. These faint structures encode information about past mergers and are sensitive to the properties and environment of the host galaxy. We investigated the relationships between LSB features and their hosts in a sample of 475 nearby massive galaxies spanning diverse environments (field, groups, Virgo cluster) using deep optical imaging from the Canada-France-Hawaii Telescope (MATLAS, UNIONS/CFIS, VESTIGE, NGVS). Using Jafar, an online annotation tool, we manually annotated tidal features and extended stellar haloes, including 199 tidal tails and 100 streams. Geometric and photometric measurements were extracted to analyse their dependence on galaxy mass, environment, and internal kinematics. At our surface brightness limit of 29 mag$\,$arcsec$^{-2}$, tidal features and stellar haloes contribute 2% and 10% of total galaxy luminosity, respectively. Tidal features are detected in 36% of galaxies, with none fainter than 27.8 mag$\,$arcsec$^{-2}$. The most massive galaxies are twice as likely to host tidal debris, and for early-type galaxies their halos are twice as luminous as those in lower-mass systems, a trend not observed in late-type galaxies. Although small-scale interactions increase the frequency of tidal features, the large-scale environment does not influence it. An anticorrelation between this frequency and rotational support is found, but may reflect the mass-driven effect. We release our database of annotated features for deep learning applications. Our findings confirm that galaxy mass is the dominant factor influencing tidal feature prevalence, consistent with hierarchical formation models.

astro-ph.GA↗
arXiv2025

Candidate Dark Galaxy-2: Validation and Analysis of an Almost Dark Galaxy in the Perseus Cluster

Candidate Dark Galaxy-2 (CDG-2) is a potential dark galaxy consisting of four globular clusters (GCs) in the Perseus cluster, first identified in Li et al. (2025) through a sophisticated statistical method. The method searched for over-densities of GCs from a \textit{Hubble Space Telescope} (\textit{HST}) survey targeting Perseus. Using the same \textit{HST} images and the new imaging data from the \textit{Euclid} survey, we report the detection of extremely faint but significant diffuse emission around the four GCs of CDG-2. We thus have exceptionally strong evidence that CDG-2 is a galaxy. This is the first galaxy detected purely through its GC population. Under the conservative assumption that the four GCs make up the entire GC population, preliminary analysis shows that CDG-2 has a total luminosity of $L_{V, \mathrm{gal}}= 6.2\pm{3.0} \times 10^6 L_{\odot}$ and a minimum GC luminosity of $L_{V, \mathrm{GC}}= 1.03\pm{0.2}\times 10^6 L_{\odot}$. Our results indicate that CDG-2 is one of the faintest galaxies having associated GCs, while at least $\sim 16.6\%$ of its light is contained in its GC population. This ratio is likely to be much higher ($\sim 33\%$) if CDG-2 has a canonical GC luminosity function (GCLF). In addition, if the previously observed GC-to-halo mass relations apply to CDG-2, it would have a minimum dark matter halo mass fraction of $99.94\%$ to $99.98\%$. If it has a canonical GCLF, then the dark matter halo mass fraction is $\gtrsim 99.99\%$. Therefore, CDG-2 may be the most GC dominated galaxy and potentially one of the most dark matter dominated galaxies ever discovered.

astro-ph.GA↗
arXiv2020

Census and classification of low-surface-brightness structures in nearby early-type galaxies from the MATLAS survey

The morphology of galaxies gives essential constraints on the models of galaxy evolution. The morphology of the features in the low-surface-brightness regions of galaxies has not been fully explored yet because of observational difficulties. Here we present the results of our visual inspections of very deep images of a large volume-limited sample of 177 nearby massive early-type galaxies (ETGs) from the MATLAS survey. The images reach a surface-brightness limit of $28.5-29$ mag arcsec$^{-2}$ in the $g'$ band. Using a dedicated navigation tool and questionnaire, we looked for structures at the outskirts of the galaxies such as tidal shells, streams, tails, disturbed outer isophotes or peripheral star-forming disks, and simultaneously noted the presence of contaminating sources, such as Galactic cirrus. We also inspected internal sub-structures such as bars and dust lanes. We discuss the reliability of this visual classification investigating the variety of answers made by the participants. We present the incidence of these structures and the trends of the incidence with the mass of the host galaxy and the density of its environment. We find an incidence of shells, stream and tails of approximately 15%, about the same for each category. For galaxies with masses over $10^{11}$ M$_\odot$, the incidence of shells and streams increases about 1.7 times. We also note a strong unexpected anticorrelation of the incidence of Galactic cirrus with the environment density of the target galaxy. Correlations with other properties of the galaxies, and comparisons to model predictions, will be presented in future papers.

astro-ph.GA↗
arXiv2017

Galaxy And Mass Assembly: Automatic Morphological Classification of Galaxies Using Statistical Learning

We apply four statistical learning methods to a sample of $7941$ galaxies ($z<0.06$) from the Galaxy and Mass Assembly (GAMA) survey to test the feasibility of using automated algorithms to classify galaxies. Using $10$ features measured for each galaxy (sizes, colours, shape parameters \& stellar mass) we apply the techniques of Support Vector Machines (SVM), Classification Trees (CT), Classification Trees with Random Forest (CTRF) and Neural Networks (NN), returning True Prediction Ratios (TPRs) of $75.8\%$, $69.0\%$, $76.2\%$ and $76.0\%$ respectively. Those occasions whereby all four algorithms agree with each other yet disagree with the visual classification (`unanimous disagreement') serves as a potential indicator of human error in classification, occurring in $\sim9\%$ of ellipticals, $\sim9\%$ of Little Blue Spheroids, $\sim14\%$ of early-type spirals, $\sim21\%$ of intermediate-type spirals and $\sim4\%$ of late-type spirals \& irregulars. We observe that the choice of parameters rather than that of algorithms is more crucial in determining classification accuracy. Due to its simplicity in formulation and implementation, we recommend the CTRF algorithm for classifying future galaxy datasets. Adopting the CTRF algorithm, the TPRs of the 5 galaxy types are : E, $70.1\%$; LBS, $75.6\%$; S0-Sa, $63.6\%$; Sab-Scd, $56.4\%$ and Sd-Irr, $88.9\%$. Further, we train a binary classifier using this CTRF algorithm that divides galaxies into spheroid-dominated (E, LBS \& S0-Sa) and disk-dominated (Sab-Scd \& Sd-Irr), achieving an overall accuracy of $89.8\%$. This translates into an accuracy of $84.9\%$ for spheroid-dominated systems and $92.5\%$ for disk-dominated systems.

astro-ph.GA↗
arXiv2017

Calibrating the Planck Cluster Mass Scale with Cluster Velocity Dispersions

We measure the Planck cluster mass bias using dynamical mass measurements based on velocity dispersions of a subsample of 17 Planck-detected clusters. The velocity dispersions were calculated using redshifts determined from spectra obtained at Gemini observatory with the GMOS multi-object spectrograph. We correct our estimates for effects due to finite aperture, Eddington bias and correlated scatter between velocity dispersion and the Planck mass proxy. The result for the mass bias parameter, $(1-b)$, depends on the value of the galaxy velocity bias $b_v$ adopted from simulations: $(1-b)=(0.51\pm0.09) b_v^3$. Using a velocity bias of $b_v=1.08$ from Munari et al., we obtain $(1-b)=0.64\pm 0.11$, i.e, an error of 17% on the mass bias measurement with 17 clusters. This mass bias value is consistent with most previous weak lensing determinations. It lies within $1σ$ of the value needed to reconcile the Planck cluster counts with the Planck primary CMB constraints. We emphasize that uncertainty in the velocity bias severely hampers precision measurements of the mass bias using velocity dispersions. On the other hand, when we fix the Planck mass bias using the constraints from Penna-Lima et al., based on weak lensing measurements, we obtain a positive velocity bias $b_v \gtrsim 0.9$ at $3σ$.

astro-ph.CO↗
arXiv2016

Star formation and black hole accretion activity in rich local clusters of galaxies

We present a study of the star formation and central black hole accretion activity of the galaxies hosted in the two nearby (z$\sim$0.2) rich galaxy clusters Abell 983 and 1731. Aims: We are able to quantify both the obscured and unobscured star formation rates, as well as the presence of active galactic nuclei (AGN) as a function of the environment in which the galaxy is located. Methods: We targeted the clusters with unprecedented deep infrared Spitzer observations (0.2 mJy @ 24 micron), near-IR Palomar imaging and optical WIYN spectroscopy. The extent of our observations ($\sim$ 3 virial radii) covers the vast range of possible environments, from the very dense cluster centre to the very rarefied cluster outskirts and accretion regions. Results: The star forming members of the two clusters present star formation rates comparable with those measured in coeval field galaxies. The analysis of the spatial arrangement of the spectroscopically confirmed members reveals an elongated distribution for A1731 with respect to the more uniform distribution of A983. The emerging picture is compatible with A983 being a fully evolved cluster, in contrast with the still actively accreting A1731. Conclusions: The analysis of the specific star formation rate reveals evidence of on-going galaxy pre-processing along A1731's filament-like structure. Furthermore, the decrease in the number of star forming galaxies and AGN towards the cluster cores suggests that the cluster environment is accelerating the ageing process of galaxies and blocking further accretion of the cold gas that fuels both star formation and black hole accretion activity.

astro-ph.GA↗
arXiv2016

Determining Type Ia Supernovae Host galaxy extinction probabilities and a statistical approach to estimating the absorption-to-reddening ratio $R_V$

We investigate limits on the extinction values of Type Ia supernovae to statistically determine the most probable color excess, E(B-V), with galactocentric distance, and use these statistics to determine the absorption-to-reddening ratio, $R_V$, for dust in the host galaxies. We determined pixel-based dust mass surface density maps for 59 galaxies from the Key Insight on Nearby Galaxies: a Far-Infrared Survey with \textit{Herschel} (KINGFISH, Kennicutt et al. (2011)). We use Type Ia supernova spectral templates (Hsiao et al. 2007) to develop a Monte Carlo simulation of color excess E(B-V) with $R_V$ = 3.1 and investigate the color excess probabilities E(B-V) with projected radial galaxy center distance. Additionally, we tested our model using observed spectra of SN 1989B, SN 2002bo and SN 2006X, which occurred in three KINGFISH galaxies. Finally, we determined the most probable reddening for Sa-Sap, Sab-Sbp, Sbc-Scp, Scd-Sdm, S0 and Irregular galaxy classes as a function of $R/R_{25}$. We find that the largest expected reddening probability are in Sab-Sb and Sbc-Sc galaxies, while S0 and Irregulars are very dust poor. We present a new approach for determining the absorption-to-reddening ratio $R_V$ using color excess probability functions, and find for a sample of 21 SNe Ia observed in Sab-Sbp galaxies, and 34 SNe in Sbc-Scp, an $R_V$ of 2.71 $\pm$ 1.58 and $R_V$ = 1.70 $\pm$ 0.38 respectively.

astro-ph.GA↗
arXiv2007

A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems

We have conducted a long slit search for low surface brightness Lyman-alpha emitters at redshift 2.67 < z < 3.75. A 92 hour long exposure with VLT/FORS2 down to a 1-sigma surface brightness detection limit of 8x10^-20 erg/cm2/s/sqarcsec yielded a sample of 27 single line emitters with fluxes of a few times 10^-18 erg/s/cm2. We present arguments that most objects are indeed Lyman-alpha. The large comoving number density, the large covering factor, dN/dz ~ 0.2-1, and the often extended Lyman-alpha emission suggest that the emitters be identified with the elusive host population of damped Lyman-alpha systems (DLAS) and high column density Lyman limit systems. A small inferred star formation rate, perhaps supplanted by cooling radiation, appears to energetically dominate the Lyman-alpha emission, and is consistent with the low metallicity, low dust content, and theoretically inferred low masses of DLAS, and with the relative lack of success of earlier searches for their optical counterparts. (abridged)

astro-ph↗
arXiv2007

Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. II. 70 micron Imaging

The absolute calibration and characterization of the Multiband Imaging Photometer for Spitzer (MIPS) 70 micron coarse- and fine-scale imaging modes are presented based on over 2.5 years of observations. Accurate photometry (especially for faint sources) requires two simple processing steps beyond the standard data reduction to remove long-term detector transients. Point spread function (PSF) fitting photometry is found to give more accurate flux densities than aperture photometry. Based on the PSF fitting photometry, the calibration factor shows no strong trend with flux density, background, spectral type, exposure time, or time since anneals. The coarse-scale calibration sample includes observations of stars with flux densities from 22 mJy to 17 Jy, on backgrounds from 4 to 26 MJy sr^-1, and with spectral types from B to M. The coarse-scale calibration is 702 +/- 35 MJy sr^-1 MIPS70^-1 (5% uncertainty) and is based on measurements of 66 stars. The instrumental units of the MIPS 70 micron coarse- and fine-scale imaging modes are called MIPS70 and MIPS70F, respectively. The photometric repeatability is calculated to be 4.5% from two stars measured during every MIPS campaign and includes variations on all time scales probed. The preliminary fine-scale calibration factor is 2894 +/- 294 MJy sr^-1 MIPS70F^-1 (10% uncertainty) based on 10 stars. The uncertainty in the coarse- and fine-scale calibration factors are dominated by the 4.5% photometric repeatability and the small sample size, respectively. The 5-sigma, 500 s sensitivity of the coarse-scale observations is 6-8 mJy. This work shows that the MIPS 70 micron array produces accurate, well calibrated photometry and validates the MIPS 70 micron operating strategy, especially the use of frequent stimulator flashes to track the changing responsivities of the Ge:Ga detectors.

astro-ph↗