scholarly journals Unveiling forming star clusters in the young Universe

2019 ◽  
Vol 14 (S351) ◽  
pp. 233-237
Author(s):  
E. Vanzella ◽  
F. Calura ◽  
M. Meneghetti ◽  
G. B. Caminha ◽  
A. Mercurio ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Gravitational Lensing ◽  
Massive Star ◽  
High Redshift ◽  
Star Clusters ◽  
Star Forming ◽  
Strong Gravitational Lensing ◽  
Deep Imaging ◽  
Look Back

AbstractThe identification of young massive star clusters (YMCs) at high redshift is becoming a real fact. We present recent results from Hubble deep imaging and VLT/ MUSE - X-Shooter observations boosted by strong gravitational lensing. We report on two parsec-scale star-forming systems at z = 6.145 and 2.37 (>10 Gyrs of look back time) currently representing the best candidate high-z YMCs. All of this also implies that the search for globular cluster precursors has already begun.

scholarly journals Massive star clusters in high-redshift star-forming galaxies seen at a 100 pc scale thanks to strong gravitational lensing

2015 ◽  
Vol 12 (S316) ◽  
pp. 111-116
Author(s):  
Miroslava Dessauges-Zavadsky ◽  
Antonio Cava ◽  
Valentina Tamburello ◽  
Daniel Schaerer ◽  
Lucio Mayer ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Gravitational Instability ◽  
High Redshift ◽  
Star Clusters ◽  
Resolving Power ◽  
Instability Criterion ◽  
Star Forming ◽  
Disk Rotation ◽  
Resolution Imaging ◽  
Stellar Masses

AbstractHigh-resolution imaging reveals clumpy morphologies among z = 1 – 3 galaxies. Most of these galaxies are dominated by disk rotation, which led to conclude that the observed clumps are generated from disk fragmentation due to gravitational instability. Despite the kpc-scale resolution attained by the most advanced facilities and numerical simulations, these clumps are barely resolved at z > 1. Thanks to the stretching and magnification power provided by gravitational lensing, we reach the sub-kpc resolving power to unveil their physics. From our literature compilation of data, we show that without lensing there is a bias toward clumps with high masses and sizes. The high-redshift clumps identified in lensed galaxies have stellar masses 2 orders of magnitude lower and a median size of 250 pc. They resemble local star clusters observed in the most intensively star-forming galaxies. The clump masses and sizes observed in lensed galaxies agree with new simulations, which show that the Toomre instability criterion overestimates the clump masses by a factor of 5 – 6.

scholarly journals From young massive star clusters to old globulars: long-term survival chances

2006 ◽  
Vol 2 (S237) ◽  
pp. 408-408
Author(s):  
Richard de Grijs
Keyword(s):  
Galaxy Formation ◽  
Massive Star ◽  
Cluster Formation ◽  
Star Clusters ◽  
Term Survival ◽  
Star Forming ◽  
Distant Galaxies ◽  
Wide Range ◽  
Galaxy Collisions

Young, massive star clusters (YMCs) are the most notable and significant end products of violent star-forming episodes triggered by galaxy collisions and close encounters. The question remains, however, whether or not at least a fraction of the compact YMCs seen in abundance in extragalactic starbursts, are potentially the progenitors of (≳10 Gyr) old globular cluster (GC)-type objects. If we could settle this issue convincingly, one way or the other, the implications of such a result would have far-reaching implications for a wide range of astrophysical questions, including our understanding of the process of galaxy formation and assembly, and the process and conditions required for star (cluster) formation. Because of the lack of a statistically significant sample of YMCs in the Local Group, however, we need to resort to either statistical arguments or to the painstaking approach of case-by-case studies of individual objects in more distant galaxies.

Evolution and Feedback Effects of High-z Star-Forming Galaxies

2015 ◽  
Vol 11 (A29B) ◽  
pp. 228-228
Author(s):  
Masami Ouchi
Keyword(s):  
Structure Formation ◽  
Gravitational Lensing ◽  
Formation Rate ◽  
Feedback Effect ◽  
Density Estimates ◽  
Feedback Effects ◽  
Planck Data ◽  
Star Forming ◽  
Deep Imaging ◽  
Open Question

AbstractI review the recent observational progresses of star-forming galaxies at a redshift up to z~10. Inconjunction with gravitational lensing magnifications, deep HST observations obtain first density estimates of UV continuum radiation given by young massive stars, and reveal that the star-formation rate density (SFRD)continuously decreases from z~2-3 to z~10. This SFRD decrease towards high-z should be explained by thecombination of the cosmic structure formation and radiative cooling+feedback effects in a halo. To decouple thecontribution of the cosmic structure formation from the SFRD decrease, the stellar-to-halo mass ratios (SHMR) ofhigh-z galaxies are derived by intensive clustering analyses with HST and Subaru survey data. The SHMR-halo massrelation shows a clear evolution from z~0 to 6, suggesting that the cooling and feedback effects are different betweenthe present and early epochs of the cosmic history. By deep imaging and spectroscopic observations, feedbacksignatures are found in 10-100 kpc-scale outflow of ionized oxgen gas identified around star-forming galaxies with andwithout an AGN heating. There are similarly-large hydrogen Lyα halos and blobs associated with high-z star-forminggalaxies, but the physical origin of these Lyα halos and blobs is an open question. At z≳6, UV radiation of ionizingphotons produced by star-forming galaxies contribute to the cosmic reionization, while it is thought that the UVradiation prevent formation of next generation stars in dwarf galaxies at the early cosmic epoch, which works as acosmological feedback effect. I discuss this reionizations cosmological feedback effect with the up-to-date resultsfrom the HST and Planck data.

scholarly journals Using young massive star clusters to understand star formation and feedback in high-redshift-like environments

2015 ◽  
Vol 75-76 ◽  
pp. 43-48
Author(s):  
S. Longmore ◽  
A. Barnes ◽  
C. Battersby ◽  
J. Bally ◽  
J.M. Diederik Kruijssen ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Redshift ◽  
Star Clusters

scholarly journals Molecular gas, stars, and dust in sub-L⋆ star-forming galaxies at z ~ 2: Evidence for universal star formation and non-universal dust-to-gas ratio

2015 ◽  
Vol 11 (S315) ◽  
pp. 254-257
Author(s):  
Miroslava Dessauges-Zavadsky ◽  
Michel Zamojski ◽  
Daniel Schaerer ◽  
Françoise Combes ◽  
Eiichi Egami ◽  
...  
Keyword(s):  
Star Formation ◽  
Gravitational Lensing ◽  
High Redshift ◽  
Clear Trend ◽  
Star Forming ◽  
Solar Metallicity ◽  
Stellar Masses ◽  
Formation Efficiency ◽  
Gas Ratio ◽  
Single Relation

AbstractCurrent star-forming galaxies (SFGs) with CO measurements at z ~ 2 suffer from a bias toward high star formation rates (SFR) and high stellar masses (M*). It is yet essential to extend the CO measurements to the more numerous z ~ 2 SFGs with LIR < L⋆ = 4× 1011 L⊙ and M* < 2.5× 1010 M⊙. We have achieved CO, stars, and dust measurements in 8 such sub-L⋆ SFGs with the help of gravitational lensing. Combined with CO-detected galaxies from the literature, we find that the LIR, L′CO(1−0) data are best-fitted with a single relation that favours a universal star formation. This picture emerges because of the enlarged star formation efficiency spread of the current z>1 SFGs sample. We show that this spread is mostly triggered by the combination of redshift, specific SFR, and M*. Finally, we find evidence for a non-universal dust-to-gas ratio (DGR) with a clear trend for a lower DGR mean in z>1 SFGs by a factor of 2 with respect to local galaxies and high-redshift sub-mm galaxies at fixed about solar metallicity.

scholarly journals Spatial Variation of CO Excitation in High-z Galaxies

2012 ◽  
Vol 8 (S292) ◽  
pp. 253-253
Author(s):  
Chelsea E. Sharon ◽  
Andrew J. Baker ◽  
Andrew I. Harris ◽  
Dieter Lutz ◽  
Linda J. Tacconi
Keyword(s):  
Spatial Variation ◽  
Gravitational Lensing ◽  
Early Stage ◽  
High Redshift ◽  
Molecular Gas ◽  
Very Large Array ◽  
Star Forming ◽  
Spatially Extended ◽  
Frequency Coverage ◽  
Extended Sources

AbstractPrevious studies of the molecular gas excitation in high-redshift galaxies have focused on galaxy-wide averages of CO line ratios. However, it is possible that these averages hide spatial variation on sub-galactic scales, disguising the true distribution and conditions of the molecular gas within star-forming galaxies. Even in the pre-ALMA era we have begun to see evidence for spatial variation of CO excitation in both rest-UV selected and submillimeter-selected galaxies at z > 2, aided both by the increased frequency coverage of the Jansky Very Large Array (allowing high-resolution observations of the CO(1–0) line, the best tracer for the coldest molecular gas) and by the benefits of gravitational lensing for spatially extended sources. We show new results for multiple high-redshift systems that reveal spatial and/or spectral variations in CO excitation, including an early-stage merger that has different conditions in its two components, thereby illustrating the need for high spatial and spectral resolution mapping in order to accurately characterize the molecular ISM in high-z galaxies.

scholarly journals A near-infrared morphological comparison of high-redshift submillimetre and radio galaxies: massive star-forming discs versus relaxed spheroids

2011 ◽  
Vol 412 (1) ◽  
pp. 295-317 ◽  
Author(s):  
Thomas A. Targett ◽  
James S. Dunlop ◽  
Ross J. McLure ◽  
Philip N. Best ◽  
Michele Cirasuolo ◽  
...  
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
High Redshift ◽  
Radio Galaxies ◽  
Morphological Comparison ◽  
Star Forming

scholarly journals Physics of a clumpy lensed galaxy at z = 1.6

2018 ◽  
Vol 619 ◽  
pp. A15 ◽  
Author(s):  
M. Girard ◽  
M. Dessauges-Zavadsky ◽  
D. Schaerer ◽  
J. Richard ◽  
K. Nakajima ◽  
...  
Keyword(s):  
Star Formation ◽  
Gravitational Lensing ◽  
Near Infrared ◽  
High Redshift ◽  
Formation Rate ◽  
Far Infrared ◽  
Rotating Disk ◽  
Cluster Galaxy ◽  
Star Forming ◽  
The Galaxy

Observations have shown that massive star-forming clumps are present in the internal structure of high-redshift galaxies. One way to study these clumps in detail with a higher spatial resolution is by exploiting the power of strong gravitational lensing which stretches images on the sky. In this work, we present an analysis of the clumpy galaxy A68-HLS115 at z = 1.5858, located behind the cluster Abell 68, but strongly lensed by a cluster galaxy member. Resolved observations with SINFONI/VLT in the near-infrared (NIR) show Hα, Hβ, [NII], and [OIII] emission lines. Combined with images covering the B band to the far-infrared (FIR) and CO(2–1) observations, this makes this galaxy one of the only sources for which such multi-band observations are available and for which it is possible to study the properties of resolved star-forming clumps and to perform a detailed analysis of the integrated properties, kinematics, and metallicity. We obtain a stability of υrot/σ0 = 2.73 by modeling the kinematics, which means that the galaxy is dominated by rotation, but this ratio also indicates that the disk is marginally stable. We find a high intrinsic velocity dispersion of 80 ± 10 km s−1 that could be explained by the high gas fraction of fgas = 0.75 ± 0.15 observed in this galaxy. This high fgas and the observed sSFR of 3.12 Gyr−1 suggest that the disk turbulence and instabilities are mostly regulated by incoming gas (available gas reservoir for star formation). The direct measure of the Toomre stability criterion of Qcrit = 0.70 could also indicate the presence of a quasi-stable thick disk. Finally, we identify three clumps in the Hα map which have similar velocity dispersions, metallicities, and seem to be embedded in the rotating disk. These three clumps contribute together to ∼40% on the SFRHα of the galaxy and show a star formation rate density about ∼100 times higher than HII regions in the local Universe.

scholarly journals The [O iii]+H β equivalent width distribution at z ≃ 7: implications for the contribution of galaxies to reionization

2020 ◽  
Vol 500 (4) ◽  
pp. 5229-5248
Author(s):  
Ryan Endsley ◽  
Daniel P Stark ◽  
Jacopo Chevallard ◽  
Stéphane Charlot
Keyword(s):  
Star Formation ◽  
Standard Deviation ◽  
Equivalent Width ◽  
Production Efficiency ◽  
Massive Star ◽  
Star Clusters ◽  
Strong Variation ◽  
Star Forming ◽  
Width Distribution ◽  
Intense Star Formation

ABSTRACT We quantify the distribution of [O iii]+H β line strengths at z ≃ 7 using a sample of 20 bright ($\mathrm{M}_{\mathrm{UV}}^{}$ ≲ –21) galaxies. We select these systems over wide-area fields (2.3 deg2 total) using a new colour-selection that precisely selects galaxies at z ≃ 6.63–6.83, a redshift range where blue Spitzer/IRAC [3.6]−[4.5] colours unambiguously indicate strong [O iii]+H β emission. These 20 galaxies suggest a lognormal [O iii]+H β EW distribution with median EW = 759$^{+112}_{-113}$ Å and standard deviation = 0.26$^{+0.06}_{-0.05}$ dex. We find no evidence for strong variation in this EW distribution with UV luminosity. The typical [O iii]+H β EW at z ≃ 7 implied by our sample is considerably larger than that in massive star-forming galaxies at z ≃ 2, consistent with a shift towards larger average sSFR (4.4 Gyr−1) and lower metallicities (0.16 Z⊙). We also find evidence for the emergence of a population with yet more extreme nebular emission ([O iii]+H β EW &gt; 1200 Å) that is rarely seen at lower redshifts. These objects have extremely large sSFR (&gt;30 Gyr−1), as would be expected for systems undergoing a burst or upturn in star formation. While this may be a short-lived phase, our results suggest that 20 per cent of the z ≃ 7 population has such extreme nebular emission, implying that galaxies likely undergo intense star formation episodes regularly at z &gt; 6. We argue that this population may be among the most effective ionizing agents in the reionization era, both in terms of photon production efficiency and escape fraction. We furthermore suggest that galaxies passing through this large sSFR phase are likely to be very efficient in forming bound star clusters.

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