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BLUEPRINT: Blue-dominant Lyman-alpha (Ly$α$) emission as an evidence of gas inflow in ultra-low-mass galaxies at z = 3

Tamal Mukherjee, Zhihui Li, Tayyaba Zafar, Themiya Nanayakkara, Davide Tornotti, Luca Costantin, Aalia Imam Uzma

Abstract

We report the detection of a clumpy, blue-dominated Ly$α$ emission at z = 3.066 located in the heart of a cosmic web filament in the MUSE eXtremely Deep Field (MXDF), spatially associated with the formation of two compact star-forming regions revealed by deep JWST/NIRCam imaging. Gas accretion in these regions is indicated by the blue-dominated Ly$α$ profiles, spectral signatures that are rarely observed. Radiative transfer simulation of the Ly$α$ profile using a clumpy multiphase model suggests a radial inflow of gas clumps with a velocity of 100 km/s. Embedded in this Ly$α$ structure, we find that the associated main galaxy dominates the stellar mass budget, while the two compact ultra-low-mass systems ($\log(M_\star/M_\odot) = 6.3\text{-}6.9$) have formed the bulk of their stellar mass in less than 7 Myr. These two components also have high specific star-formation rates, and elevated ionisation parameters, consistent with recent bursty star formation. This system provides direct observational evidence that how gas accretion, most likely from cosmic web, can induce starburst in ultra-low-mass galaxies.

BLUEPRINT: Blue-dominant Lyman-alpha (Ly$α$) emission as an evidence of gas inflow in ultra-low-mass galaxies at z = 3

Abstract

We report the detection of a clumpy, blue-dominated Ly emission at z = 3.066 located in the heart of a cosmic web filament in the MUSE eXtremely Deep Field (MXDF), spatially associated with the formation of two compact star-forming regions revealed by deep JWST/NIRCam imaging. Gas accretion in these regions is indicated by the blue-dominated Ly profiles, spectral signatures that are rarely observed. Radiative transfer simulation of the Ly profile using a clumpy multiphase model suggests a radial inflow of gas clumps with a velocity of 100 km/s. Embedded in this Ly structure, we find that the associated main galaxy dominates the stellar mass budget, while the two compact ultra-low-mass systems () have formed the bulk of their stellar mass in less than 7 Myr. These two components also have high specific star-formation rates, and elevated ionisation parameters, consistent with recent bursty star formation. This system provides direct observational evidence that how gas accretion, most likely from cosmic web, can induce starburst in ultra-low-mass galaxies.
Paper Structure (19 sections, 6 figures, 2 tables)

This paper contains 19 sections, 6 figures, 2 tables.

Table of Contents

  1. INTRODUCTION
  2. Data
  3. MUSE IFU
  4. HST Imaging
  5. JWST NIRCam and MIRI Imaging
  6. JWST NIRSpec spectroscopy
  7. Methods and analysis
  8. Spatially-resolved Ly$\alpha$
  9. Radiative transfer modeling using a multiphase clumpy model
  10. Spectral energy distribution modeling using Bagpipes
  11. Emission line diagnostics
  12. Results and discussions
  13. Ly$\alpha$ as an evidence of clump radial inflow
  14. Stellar populations and star-formation activities
  15. NFW density profile modeling
  16. ...and 4 more sections

Figures (6)

  • Figure 1: Continuum-subtracted Ly$\alpha$ narrow-band image (left) obtained by collapsing the MUSE datacube over 4925–4960 Å, HST/ACS F775W image (middle) and JWST/NIRCam F200W image (right). The white contour in the left panel shows 1.5 $\sigma$ significance level. The yellow circle shows the location of the primary galaxy and white circle represents the same for the companion galaxy. The inset in the top-right corner of the right panel presents a zoomed-in RGB composite of the region containing the three galaxies, constructed using JWST/NIRCam F115W, F200W, and F336W filters.
  • Figure 2: Radiative transfer modeling of spatially-resolved Ly$\alpha$ profiles (left and right panel) extracted from Voronoi-binned regions (middle panel), along the direction 1 $\rightarrow$ 2. The observed line profiles are shown in black (with uncertainties shown in gray) and the best-fit models are shown in red. The vertical dashed line represents line centre velocity corresponding to a systemic redshift of $z = 3.066$, obtained from JWST/NIRSpec spectra. Middle panel shows two Voronoi-binned regions displayed on the Ly$\alpha$ narrowband (NB) image within 1.5 $\sigma$ significance, centred on the pixel with maximum Ly$\alpha$ surface-brightness.
  • Figure 3: Deblended segmentation map of the NIRCam F200W and F210M filter showing segmented region for primary-1 along with the primary galaxy
  • Figure 4: NFW dark matter density profiles for the system at $z= 3.066$. The red dashed curve shows the NFW profile of the Primary galaxy halo (including the compact Primary–1 component), the blue dashed curve shows the Companion modeled as a sub-halo placed at a projected offset of 6.5 kpc, and the solid green curve shows the combined density profile.
  • Figure 5: Top panle: JWST/NIRSpec medium resolution G235M F170LP spectrum obtained from the location of the primary galaxy (NIRSpec ID = 118073). Bottom Panel: Low resolution PRISM spectrum of companion galaxy.
  • ...and 1 more figures