Pearls on a string: Dark and bright galaxies on a strikingly straight and narrow filament

Abstract

We identify a chain of galaxies along an almost straight line in the nearby Universe with a projected length of ~5 Mpc. The galaxies are distributed within projected distances of only 7-105 kpc from the axis of the identified filament. They have redshifts in a very small range of z=0.0361-0.0370 so that their radial velocities are consistent with galaxy proper motions. The filament galaxies are mainly star-forming and have stellar masses in a range of $10^{9.1}-10^{10.7}{\mathrm{M}}_{\odot }$. We search for systems with similar geometrical properties in the full-sky mock galaxy catalogue of the MillenniumTNG simulations and find that although such straight filaments are unusual and rare, they are predicted by $\Lambda$CDM simulations (4% incidence). We study the cold HI gas in a 1.3 Mpc section of the filament through HI-21cm emission line observations and detect eleven HI sources, many more than expected from the HI mass function in a similar volume. They have HI masses $10^{8.5}-10^{9.5}{\mathrm{M}}_{\odot }$ and are mostly within ~120 kpc projected distance from the filament axis. None of these HI sources has a confirmed optical counterpart. Their darkness together with their large HI-21cm line-widths indicate that they contain gas that might not yet be virialized. These clouds must be marking the peaks of the dark matter and HI distributions over large scales within the filament. The presence of such gas clouds around the filament spines is predicted by simulations, but this is the first time that the existence of such clouds in a filament is observationally confirmed.

Published in ApJL. Main figures: Fig. 1 and Fig. 3

References in corpus (29)

• Cold streams in early massive hot haloes as the main mode of galaxy formation
• The Atlas3D project -- XXIX. The new look of early-type galaxies and surrounding fields disclosed by extremely deep optical images
• SoFiA: a flexible source finder for 3D spectral line data
• Gas filaments of the cosmic web located around active galaxies in a proto-cluster
• SoFiA 2 -- An automated, parallel HI source finding pipeline for the WALLABY survey
• The VIMOS Public Extragalactic Redshift Survey (VIPERS): Galaxy segregation inside filaments at $z\simeq 0.7$
• A filament of dark matter between two clusters of galaxies
• From voids to filaments: environmental transformations of galaxies in the SDSS
• The alignment of satellite galaxies and cosmic filaments: observations and simulations
• New HI scaling relations to probe the HI content of galaxies via global HI-deficiency maps
• The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems
• Properties of gas phases around cosmic filaments at z=0 in the Illustris-TNG simulation
• The MillenniumTNG Project: High-precision predictions for matter clustering and halo statistics
• (Almost) Dark HI Sources in the ALFALFA Survey: The Intriguing Case of HI1232+20
• First detection of stacked X-ray emission from cosmic web filaments
• Redshift-Independent Distances in the NASA/IPAC Extragalactic Database: Methodology, Content and Use of NED-D
• Virgo Filaments I: Processing of gas in cosmological filaments around the Virgo cluster
• Large-scale filamentary structures around the Virgo cluster revisited
• Stacking the Cosmic Web in Fluorescent Lyman alpha Emission with MUSE
• The role of the cosmic web in the scatter of the galaxy stellar mass - gas metallicity relation
• A diffuse tidal dwarf galaxy destined to fade out as a "dark galaxy"
• Galaxy And Mass Assembly (GAMA): Blue spheroids within 87 Mpc
• The MillenniumTNG Project: Semi-analytic galaxy formation models on the past lightcone
• An extremely optically dim tidal feature in the gas-rich interacting galaxy group NGC 871/NGC 876/NGC 877
• The ALFALFA Almost-Dark Galaxy AGC~229101: A Two Billion Solar Mass HI Cloud with a Very Low Surface Brightness Optical Counterpart
• WALLABY pre-pilot survey: Two dark clouds in the vicinity of NGC 1395
• Deep optical imaging of the dark galaxy candidate AGESVC1 282
• The detection of a massive chain of dark HI clouds in the GAMA G23 Field
• Unusual gas structure in an otherwise normal spiral galaxy hosting GRB 171205A / SN 2017iuk

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