ORIGIN: Blind detection of faint emission line galaxies in MUSE datacubes

Mary, David; Bacon, Roland; Conseil, Simon; Piquéras, Laure; Schutz, Antony

doi:10.1051/0004-6361/201937001

Cited by 29 publications

(33 citation statements)

References 31 publications

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“…We perform two types of source detection and extraction: a blind source detection with ORIGIN and source extraction and deblending using HST prior information with ODHIN. The ORIGIN software (Mary et al 2020) has been developed to automatically detect faint line emitters in MUSE datacubes. It is optimized for the detection of compact sources with faint spatialspectral emission signatures and provides an automated and reliable estimate of the purity (i.e., related to the proportion of false discoveries).…”

Section: Source Detection and Classificationmentioning

confidence: 99%

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The MUSE Extremely Deep Field: The cosmic web in emission at high redshift

Bacon

Mary

Garel

et al. 2021

A&A

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We report the discovery of diffuse extended Lyα emission from redshift 3.1 to 4.5, tracing cosmic web filaments on scales of 2.5−4 cMpc. These structures have been observed in overdensities of Lyα emitters in the MUSE Extremely Deep Field, a 140 h deep MUSE observation located in the Hubble Ultra-Deep Field. Among the 22 overdense regions identified, five are likely to harbor very extended Lyα emission at high significance with an average surface brightness of 5 × 10−20 erg s−1 cm−2 arcsec−2. Remarkably, 70% of the total Lyα luminosity from these filaments comes from beyond the circumgalactic medium of any identified Lyα emitter. Fluorescent Lyα emission powered by the cosmic UV background can only account for less than 34% of this emission at z ≈ 3 and for not more than 10% at higher redshift. We find that the bulk of this diffuse emission can be reproduced by the unresolved Lyα emission of a large population of ultra low-luminosity Lyα emitters (< 1040 erg s−1), provided that the faint end of the Lyα luminosity function is steep (α ⪅ −1.8), it extends down to luminosities lower than 1038 − 1037 erg s−1, and the clustering of these Lyα emitters is significant (filling factor < 1/6). If these Lyα emitters are powered by star formation, then this implies their luminosity function needs to extend down to star formation rates < 10−4 M⊙ yr−1. These observations provide the first detection of the cosmic web in Lyα emission in typical filamentary environments and the first observational clue indicating the existence of a large population of ultra low-luminosity Lyα emitters at high redshift.

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Section: Source Detection and Classificationmentioning

confidence: 99%

“…As the continuum subtracted datacube we use the PCA subtracted S/N cube provided by ORIGIN. The ORIGIN process (Mary et al 2020) is efficient for removing the continuum of bright galaxies without leaving many artifacts, which can be problematic for low surface brightness detection.…”

Section: Multiscale Analysis Of Narrowband Imagesmentioning

confidence: 99%

The MUSE Extremely Deep Field: The cosmic web in emission at high redshift

Bacon

Mary

Garel

et al. 2021

A&A

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“…Based on the reduced data cubes presented in Bacon et al (2017), Inami et al (2017; hereafter I17) constructed the MUSE UDF catalog. The source detection and extraction were performed using (i) priors detected in the Hubble Space Telescope (HST) data (Rafelski et al 2015), imposing a magnitude cut at 27 in the F775W band for the mosaic field only, and (ii) the ORIGIN detection software (Mary et al 2020). A complete description of the strategy used for the catalog construction can be found in I17.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

The MUSE Hubble Ultra Deep Field Survey

Leclercq

Bacon

Verhamme

et al. 2020

A&A

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We present spatially resolved maps of six individually-detected Lyman α haloes (LAHs) as well as a first statistical analysis of the Lyman α (Lyα) spectral signature in the circum-galactic medium of high-redshift star-forming galaxies (−17.5 > MUV > −21.5) using the Multi-Unit Spectroscopic Explorer. Our resolved spectroscopic analysis of the LAHs reveals significant intrahalo variations of the Lyα line profile. Using a three-dimensional two-component model for the Lyα emission, we measured the full width at half maximum (FWHM), the peak velocity shift, and the asymmetry of the Lyα line in the core and in the halo of 19 galaxies. We find that the Lyα line shape is statistically different in the halo compared to the core (in terms of width, peak wavelength, and asymmetry) for ≈40% of our galaxies. Similarly to object-by-object based studies and a recent resolved study using lensing, we find a correlation between the peak velocity shift and the width of the Lyα line both at the interstellar and circum-galactic scales. This trend has been predicted by radiative transfer simulations of galactic winds as a result of resonant scattering in outflows. While there is a lack of correlation between the spectral properties and the spatial scale lengths of our LAHs, we find a correlation between the width of the line in the LAH and the halo flux fraction. Interestingly, UV bright galaxies (MUV < −20) show broader, more redshifted, and less asymmetric Lyα lines in their haloes. The most significant correlation found is for the FWHM of the line and the UV continuum slope of the galaxy, suggesting that the redder galaxies have broader Lyα lines. The generally broad and red line shapes found in the halo component suggest that the Lyα haloes are powered either by scattering processes through an outflowing medium, fluorescent emission from outflowing cold clumps of gas, or a mix of both. Considering the large diversity of the Lyα line profiles observed in our sample and the lack of strong correlation, the interpretation of our results is still broadly open and underlines the need for realistic spatially resolved models of the LAHs.

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“…A final possibility related to merging activity is the presence of UV-faint or UV-dark Lyα-emitting galaxies (e.g., Bacon et al 2015;Maseda et al 2018;Mary et al 2020) in a pre-or early-stage merging configuration. However, such systems are fairly rare, with number densities of ∼ 2 − 10 × 10 −5 Mpc −3 at 3 ∼ < z ∼ < 7 from extremely deep MUSE observations, and have typical Lyα line luminosities approximately three times lower than that of our combined sample.…”

Section: Explaining the Lyα-uv Offsetsmentioning

confidence: 99%

The size and pervasiveness of Ly α–UV spatial offsets in star-forming galaxies at z ∼ 6

Lemaux

Fuller

Bradač

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We study the projected spatial offset between the ultraviolet continuum and Lyα emission for 65 lensed and unlensed galaxies in the Epoch of Reionization (5 ≤ z ≤ 7), the first such study at these redshifts, in order to understand the potential for these offsets to confuse estimates of the Lyα properties of galaxies observed in slit spectroscopy. While we find that ∼40% of galaxies in our sample show significant projected spatial offsets ($|\Delta _{\rm {Ly}\alpha -\rm {UV}}|$), we find a relatively modest average projected offset of $|\widetilde{\Delta }_{\rm {Ly}\alpha -\rm {UV}}|$ = 0.61±0.08 proper kpc for the entire sample. A small fraction of our sample, ∼10%, exhibit offsets in excess of 2 proper kpc, with offsets seen up to ∼4 proper kpc, sizes that are considerably larger than the effective radii of typical galaxies at these redshifts. An internal comparison and a comparison to studies at lower redshift yielded no significant evidence of evolution of $|\Delta _{\rm {Ly}\alpha -\rm {UV}}|$ with redshift. In our sample, UV-bright galaxies ($\widetilde{L_{UV}}/L^{\ast }_{UV}=0.67$) showed offsets a factor of three greater than their fainter counterparts ($\widetilde{L_{UV}}/L^{\ast }_{UV}=0.10$), 0.89±0.18 vs. 0.27±0.05 proper kpc, respectively. The presence of companion galaxies and early-stage merging activity appeared to be unlikely causes of these offsets. Rather, these offsets appear consistent with a scenario in which internal anisotropic processes resulting from stellar feedback, which is stronger in UV-brighter galaxies, facilitate Lyα fluorescence and/or backscattering from nearby or outflowing gas. The reduction in the Lyα flux due to offsets was quantified. It was found that the differential loss of Lyα photons for galaxies with average offsets is not, if corrected for, a limiting factor for all but the narrowest slit widths (<0.4″). However, for the largest offsets, if they are mostly perpendicular to the slit major axis, slit losses were found to be extremely severe in cases where slit widths of ≤1″ were employed, such as those planned for James Webb Space Telescope/NIRSpec observations.

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ORIGIN: Blind detection of faint emission line galaxies in MUSE datacubes

Cited by 29 publications

References 31 publications

The MUSE Extremely Deep Field: The cosmic web in emission at high redshift

The MUSE Extremely Deep Field: The cosmic web in emission at high redshift

The MUSE Hubble Ultra Deep Field Survey

The size and pervasiveness of Ly α–UV spatial offsets in star-forming galaxies at z ∼ 6

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