Low-luminosity galaxies in the early universe have observed sizes similar to star cluster complexes

Abstract

We compare the sizes and luminosities of faint $z=6$-8 galaxies magnified by the Hubble Frontier Fields (HFF) clusters with star-forming regions, as well as more evolved objects, in the nearby universe. Our high-redshift comparison sample includes 333 z=6-8 galaxies, for which size measurements were made as part of a companion study where lensing magnifications were estimated from various public models. Accurate size measurements for these sources are complicated by the lens model uncertainties, but other results and arguments suggest that faint galaxies are small, as discussed in a companion study. The measured sizes for sources in our comparison sample range from <50 pc to ~500 pc. For many of the lowest luminosity sources, extremely small sizes are inferred, reaching individual sizes as small as 10-30 pc, with several sources in the 10-15 pc range with our conservative magnification limits. The sizes and luminosities are similar to those of single star cluster complexes like 30 Doradus in the lower-redshift universe and -- in a few cases -- super star clusters. The identification of these compact, faint star-forming sources in the z~6-8 universe also allows us to set upper limits on the proto-globular cluster LF at z~6. By comparisons of the counts and sizes with recent models, we rule out (with some caveats) proto-globular cluster formation scenarios favoring substantial (xi=10) post-formation mass loss and set useful upper limits on others. Our size results suggest we may be very close to discovering a bona-fide population of forming globular clusters at high redshift.

arXiv comment14 pages, 5 figures, AJ, in press. arXiv admin note: substantial text overlap with arXiv:1711.02090

References in corpus (107)

• Planck 2015 results. XIII. Cosmological parameters
• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Embedded Clusters in Molecular Clouds
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• SINGS: The SIRTF Nearby Galaxies Survey
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• The Atlas3D project -- I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Extragalactic Globular Clusters and Galaxy Formation
• Dynamical evolution of star clusters in tidal fields
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The Frontier Fields: Survey Design
• A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters
• UV Luminosity Functions from 132 z~7 and z~8 Lyman-Break Galaxies in the ultra-deep HUDF09 and wide-area ERS WFC3/IR Observations
• Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster
• Starbursts and Star Clusters in the Ultraviolet
• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• New Determinations of the UV Luminosity Functions from z~9 to z~2 show a remarkable consistency with halo growth and a constant star formation efficiency
• Directly Observing the Galaxies Likely Responsible for Reionization
• The size - virial radius relation of galaxies
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. V. Constraints on Formation Scenarios
• Globular clusters as the relics of regular star formation in 'normal' high-redshift galaxies
• A Catalog of Globular Cluster Systems: What Determines the Size of a Galaxy's Globular Cluster Population?
• Full-Data Results of Hubble Frontier Fields: UV Luminosity Functions at $z\sim 6-10$ and a Consistent Picture of Cosmic Reionization
• The ACS Virgo Cluster Survey. VII. Resolving the Connection Between Globular Clusters and Ultra-Compact Dwarf Galaxies
• The z~6 Luminosity Function Fainter than -15 mag from the Hubble Frontier Fields: The Impact of Magnification Uncertainties
• z~7 Galaxies in the HUDF: First Epoch WFC3/IR Results
• The E-MOSAICS Project: simulating the formation and co-evolution of galaxies and their star cluster populations
• Galaxy Size Evolution at High Redshift and Surface Brightness Selection Effects: Constraints from the Hubble Ultra Deep Field
• The Frontier Fields Lens Modeling Comparison Project
• A Pair of Lensed Galaxies at z=4.92 in the Field of CL1358+62
• On the Star Formation Rate - Brightest Cluster Relation: Estimating the peak SFR in post-merger galaxies
• Lens models and magnification maps of the six Hubble Frontier Fields clusters
• The Relationships Among Compact Stellar Systems: A Fresh View of Ultra Compact Dwarfs
• The AIMSS Project I: Bridging the Star Cluster - Galaxy Divide
• Paving the way for the JWST: witnessing globular cluster formation at z>3
• A New Method for Estimating Dark Matter Halo Masses using Globular Cluster Systems
• Globular cluster formation in the context of galaxy formation and evolution
• Size--luminosity relations and UV luminosity functions at $z=6-9$ simultaneously derived from the complete Hubble Frontier Fields data
• Resolved spectroscopy of gravitationally lensed galaxies: global dynamics and star-forming clumps on ~100pc scales
• The local space density of Sb-Sdm galaxies as function of their scalesize, surface brightness and luminosity
• The dynamical mass of the young cluster W3 in NGC 7252: Heavy-Weight globular cluster or ultra compact dwarf galaxy ?
• Hierarchical Star Formation in M51: Star/Cluster Complexes
• Evolution of the Sizes of Galaxies over 7<z<12 Revealed by the 2012 Hubble Ultra Deep Field Campaign
• The E-MOSAICS project: tracing galaxy formation and assembly with the age-metallicity distribution of globular clusters
• HST morphologies of local Lyman break galaxy analogs I: Evidence for starbursts triggered by merging
• Frontier Fields: High-Redshift Predictions and Early Results
• Hubble Space Telescope H-alpha imaging of star-forming galaxies at z = 1-1.5: evolution in the size and luminosity of giant HII regions
• A new perspective on globular clusters, their initial mass function, and their contribution to the stellar halo and to cosmic reionisation
• Scaling Relations of Star-Forming Regions: from kpc-size clumps to HII regions
• Massive Star cluster formation under the microscope at z=6
• Ionising the Intergalactic Medium by Star Clusters: The first empirical evidence
• The ASTRODEEP Frontier Fields Catalogues: I - Multiwavelength photometry of Abell-2744 and MACS-J0416
• The Sizes and Luminosities of Massive Star Clusters
• Extremely metal-poor star-forming galaxies. New detections and general morphological and photometric properties
• The sizes of $z\sim 6-8$ lensed galaxies from the Hubble Frontier Fields Abell 2744 data
• A Population of Compact Elliptical Galaxies Detected with the Virtual Observatory
• Probing cluster formation under extreme conditions: massive star clusters in blue compact galaxies
• A Spatially Resolved Map of the Kinematics, Star-Formation and Stellar Mass Assembly in a Star-Forming Galaxy at z=4.9
• Self-consistent proto-globular cluster formation in cosmological simulations of high-redshift galaxies
• DYNAMO-HST Survey: Clumps in Nearby Massive Turbulent Disks and the Effects of Clump Clustering on Kiloparsec Scale Measurements of Clumps
• The star cluster - field star connection in nearby spiral galaxies. II. Field star and cluster formation histories and their relation
• Globular Cluster Mass Loss in the Context of Multiple Populations
• Bright globular clusters in NGC 5128: the missing link between young massive clusters and evolved massive objects
• Young Star Cluster Complexes in NGC 4038/39: Integral field spectroscopy using VIMOS-VLT
• Magnifying the early episodes of star formation: super star clusters at cosmological distances
• The early-type dwarf galaxy population of the Hydra I cluster
• Back to the Future: Estimating Initial Globular Cluster Masses from their Present Day Stellar Mass Functions
• The Sizes of Candidate $z\sim 9-10$ Galaxies: confirmation of the bright CANDELS sample and relation with luminosity and mass
• Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459: Star Formation down to 30 parsec scales
• Simulating galaxies in the reionization era with FIRE-2: morphologies and sizes
• Extremely Metal-Poor Representatives Explored by the Subaru Survey (EMPRESS). I. A Successful Machine Learning Selection of Metal-Poor Galaxies and the Discovery of a Galaxy with M*<10^6 M_sun and 0.016 Z_sun
• Extremely Small Sizes for Faint z~2-8 Galaxies in the Hubble Frontier Fields: A Key Input For Establishing their Volume Density and UV Emissivity
• The Globular Cluster - Dark Matter Halo Connection
• Finding Forming Globular Clusters at High Redshifts
• Early Low-Mass Galaxies and Star-Cluster Candidates at z~6-9 Identified by the Gravitational Lensing Technique and Deep Optical/Near-Infrared Imaging
• Constraining globular cluster formation through studies of young massive clusters - II. A Single Stellar Population Young Massive Cluster in NGC 34
• On the stellar masses of giant clumps in distant star-forming galaxies
• The Search for Multiple Populations in Magellanic Cloud Clusters III: No evidence for Multiple Populations in the SMC cluster NGC 419
• A Magnified View of the Kinematics and Morphology of RCSGA 032727-132609: Zooming in on a Merger at z=1.7
• A large population of ultra-compact dwarf galaxies in the Hydra I cluster
• The Little Engines That Could? Globular Clusters Contribute Significantly to Reionization-era Star Formation
• A search for ultra-compact dwarf galaxies in the Centaurus galaxy cluster
• High resolution study of the cluster complexes in a lensed spiral at redshift ~1.5; constraints on the bulge formation and disk evolution
• In-spiraling Clumps in Blue Compact Dwarf Galaxies
• Formation of Metal-Poor Globular Clusters in Lyman alpha Emitting Galaxies in the Early Universe
• Integral field near-infrared spectroscopy of II Zw 40
• Globular Cluster Formation at High Density: A model for Elemental Enrichment with Fast Recycling of Massive-Star Debris
• Luminosity profiles and sizes of massive star clusters in NGC 7252
• The chemical composition of Ultracompact Dwarf Galaxies in the Virgo and Fornax Clusters
• Compact Stellar Systems around NGC 1399
• Searches for Ultra-Compact Dwarf Galaxies in Galaxy Groups
• The VIMOS Ultra-Deep Survey: A major merger origin for the high fraction of galaxies at $2<z<6$ with two bright clump
• Is the Escape Velocity in Star Clusters Linked to Extended Star Formation Histories? Using NGC 7252: W3 as a Test Case
• Very low-luminosity galaxies in the early universe have observed sizes similar to single star cluster complexes
• Strong-Lensing Analysis of MS 1358.4+6245: New Multiple Images and Implications for the Well-Resolved z=4.92 Galaxy
• Search Instructions for Globular Clusters in Formation at High Redshifts
• Origin of Giant Stellar Clumps in High-Redshift Galaxies
• Globular Clusters in High-Redshift Dwarf Galaxies: A Case Study from the Local Group
• The evolution of the UV luminosity function of globular clusters in the E-MOSAICS simulations
• EMPRESS. III. Morphology, Stellar Population, and Dynamics of Extremely Metal Poor Galaxies (EMPGs): Are EMPGs Local Analogs of High-$z$ Young Galaxies?
• Push it to the limit: Local Group constraints on high-redshift stellar mass functions for Mstar > 10^5 Msun
• Hubble Space Telescope Observations of Accretion-Induced Star Formation in the Tadpole Galaxy Kiso 5639
• Giant H II regions in the merging system NGC 3256: Are they the birthplaces of globular clusters?
• Initial Size Distribution of the Galactic Globular Cluster System
• Towards Studying Hierarchical Assembly in Real Time: A Milky Way Progenitor Galaxy at z = 2.36 under the Microscope
• Does radiative feedback make faint z>6 galaxies look small?

Cited by in corpus (1)

• Globular Clusters and Streaming Velocities: Testing the new formation channel in high-resolution cosmological simulations