High Redshift Radio Galaxies: Laboratories for Massive Galaxy and Cluster Formation in the Early Universe

ABSTRACT We report the formation of bound star clusters in a sample of high-resolution cosmological zoom-in simulations of z ≥ 5 galaxies from the Feedback In Realistic Environments project. We find that bound clusters preferentially form in high-pressure clouds with gas surface densities over $10^4\, \mathrm{ M}_{\odot }\, {\rm pc}^{-2}$, where the cloud-scale star formation efficiency is near unity and young stars born in these regions are gravitationally bound at birth. These high-pressure clouds are compressed by feedback-driven winds and/or collisions of smaller clouds/gas streams in highly gas-rich, turbulent environments. The newly formed clusters follow a power-law mass function of dN/dM ∼ M−2. The cluster formation efficiency is similar across galaxies with stellar masses of ∼107–$10^{10}\, \mathrm{ M}_{\odot }$ at z ≥ 5. The age spread of cluster stars is typically a few Myr and increases with cluster mass. The metallicity dispersion of cluster members is ∼0.08 dex in $\rm [Z/H]$ and does not depend on cluster mass significantly. Our findings support the scenario that present-day old globular clusters (GCs) were formed during relatively normal star formation in high-redshift galaxies. Simulations with a stricter/looser star formation model form a factor of a few more/fewer bound clusters per stellar mass formed, while the shape of the mass function is unchanged. Simulations with a lower local star formation efficiency form more stars in bound clusters. The simulated clusters are larger than observed GCs due to finite resolution. Our simulations are among the first cosmological simulations that form bound clusters self-consistently in a wide range of high-redshift galaxies.

Download Full-text

Lyα excess in high-redshift radio galaxies: a signature of star formation★

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2006.11371.x ◽

2007 ◽

Vol 375 (4) ◽

pp. 1299-1310 ◽

Cited By ~ 46

Author(s):

M. Villar-Martín ◽

A. Humphrey ◽

C. De Breuck ◽

R. Fosbury ◽

L. Binette ◽

...

Keyword(s):

Star Formation ◽

High Redshift ◽

Radio Galaxies

Download Full-text

Spatially resolved studies of extragalactic jets in high redshift radio galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315002239 ◽

2014 ◽

Vol 10 (S313) ◽

pp. 231-235

Author(s):

Leah K. Morabito ◽

Adam Deller ◽

J. B. R. Oonk ◽

Huub Röttgering ◽

George Miley

Keyword(s):

High Redshift ◽

Low Frequency ◽

Radio Galaxies ◽

Radio Sources ◽

Spatially Resolved ◽

Long Baseline ◽

Early Results ◽

Spectrum Radio ◽

Extragalactic Jets ◽

Frequency Survey

AbstractThe correlation between radio spectral steepness and redshift has been successfully used to find high redshift (z ⩾ 2) radio galaxies, but the origin of this relation is unknown. The ultra-steep spectra of high-z radio sources make them ideally suited for studies with the Low Band Antenna of the new Low Frequency Array, which covers 10–80 MHz and has baselines up to about 1300 km. As part of an ongoing survey, we use the longest baselines to map the low-frequency (< 70 MHz) spatial distributions along the jets of 5 bright extended steep spectrum high-z radio sources. From this, we will determine whether the spectra change over these spatially resolved sources, thereby constraining particle acceleration processes. We present early results from our low-frequency survey of ultra-steep spectrum radio galaxies. The first low frequency long baseline images of these objects are presented.

Download Full-text

High-redshift radio galaxies

The Universe at High-z, Large-Scale Structure and the Cosmic Microwave Background - Lecture Notes in Physics ◽

10.1007/bfb0102579 ◽

2007 ◽

pp. 42-52

Author(s):

George Miley

Keyword(s):

High Redshift ◽

Radio Galaxies

Download Full-text

High-redshift radio galaxies and divergence from the CMB dipole

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stx1631 ◽

2017 ◽

Vol 471 (1) ◽

pp. 1045-1055 ◽

Cited By ~ 22

Author(s):

Jacques Colin ◽

Roya Mohayaee ◽

Mohamed Rameez ◽

Subir Sarkar

Keyword(s):

High Redshift ◽

Radio Galaxies

Download Full-text

Giant quiescent haloes associated with high redshift radio galaxies

New Astronomy Reviews ◽

10.1016/s1387-6473(03)00041-1 ◽

2003 ◽

Vol 47 (4-5) ◽

pp. 291-297 ◽

Cited By ~ 7

Author(s):

M Villar-Martín

Keyword(s):

High Redshift ◽

Radio Galaxies

Download Full-text

Accurately predicting the escape fraction of ionizing photons using rest-frame ultraviolet absorption lines

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832758 ◽

2018 ◽

Vol 616 ◽

pp. A30 ◽

Cited By ~ 35

Author(s):

J. Chisholm ◽

S. Gazagnes ◽

D. Schaerer ◽

A. Verhamme ◽

J. R. Rigby ◽

...

Keyword(s):

Early Universe ◽

Rest Frame ◽

High Redshift ◽

Flux Ratio ◽

Companion Paper ◽

Absorption Lines ◽

Indirect Methods ◽

High Redshift Galaxies ◽

Lyman Continuum ◽

Redshift Galaxies

The fraction of ionizing photons that escape high-redshift galaxies sensitively determines whether galaxies reionized the early Universe. However, this escape fraction cannot be measured from high-redshift galaxies because the opacity of the intergalactic medium is large at high redshifts. Without methods to measure the escape fraction of high-redshift galaxies indirectly, it is unlikely that we will know what reionized the Universe. Here, we analyze the far-ultraviolet (UV) H I (Lyman series) and low-ionization metal absorption lines of nine low-redshift, confirmed Lyman continuum emitting galaxies. We use the H I covering fractions, column densities, and dust attenuations measured in a companion paper to predict the escape fraction of ionizing photons. We find good agreement between the predicted and observed Lyman continuum escape fractions (within 1.4σ) using both the H I and ISM absorption lines. The ionizing photons escape through holes in the H I, but we show that dust attenuation reduces the fraction of photons that escape galaxies. This means that the average high-redshift galaxy likely emits more ionizing photons than low-redshift galaxies. Two other indirect methods accurately predict the escape fractions: the Lyα escape fraction and the optical [O III]/[O II] flux ratio. We use these indirect methods to predict the escape fraction of a sample of 21 galaxies with rest-frame UV spectra but without Lyman continuum observations. Many of these galaxies have low escape fractions (fesc ≤ 1%), but 11 have escape fractions >1%. Future studies will use these methods to measure the escape fractions of high-redshift galaxies, enabling upcoming telescopes to determine whether star-forming galaxies reionized the early Universe.

Download Full-text

The SINFONI survey of powerful radio galaxies at z ~ 2: Jet-driven AGN feedback during the Quasar Era

Astronomy and Astrophysics ◽

10.1051/0004-6361/201528040 ◽

2017 ◽

Vol 599 ◽

pp. A123 ◽

Cited By ~ 27

Author(s):

N. P. H. Nesvadba ◽

C. De Breuck ◽

M. D. Lehnert ◽

P. N. Best ◽

C. Collet

Keyword(s):

Kinetic Energy ◽

Interstellar Medium ◽

Large Scale ◽

High Redshift ◽

Radio Galaxies ◽

Energy Output ◽

Host Galaxy ◽

Powerful Radio ◽

Massive Galaxies ◽

Gas Kinematics

We present VLT/SINFONI imaging spectroscopy of the rest-frame optical emission lines of warm ionized gas in 33 powerful radio galaxies at redshifts z ≳ 2, which are excellent sites to study the interplay of rapidly accreting active galactic nuclei and the interstellar medium of the host galaxy in the very late formation stages of massive galaxies. Our targets span two orders of magnitude in radio size (2−400 kpc) and kinetic jet energy (a few 1046– almost 1048 erg s-1). All sources have complex gas kinematics with broad line widths up to ~1300 km s-1. About half have bipolar velocity fields with offsets up to 1500 km s-1 and are consistent with global back-to-back outflows. The others have complex velocity distributions, often with multiple abrupt velocity jumps far from the nucleus of the galaxy, and are not associated with a major merger in any obvious way. We present several empirical constraints that show why gas kinematics and radio jets seem to be physically related in all galaxies of the sample. The kinetic energy in the gas from large scale bulk and local outflow or turbulent motion corresponds to a few 10-3 to 10-2 of the kinetic energy output of the radio jet. In galaxies with radio jet power ≳ 1047 erg s-1, the kinetic energy in global back-to-back outflows dominates the total energy budget of the gas, suggesting that bulk motion of outflowing gas encompasses the global interstellar medium. This might be facilitated by the strong gas turbulence, as suggested by recent analytical work. We compare our findings with recent hydrodynamic simulations, and discuss the potential consequences for the subsequent evolution of massive galaxies at high redshift. Compared with recent models of metal enrichment in high-z AGN hosts, we find that the gas-phase metallicities in our galaxies are lower than in most low-z AGN, but nonetheless solar or even super-solar, suggesting that the ISM we see in these galaxies is very similar to the gas from which massive low-redshift galaxies formed most of their stars. This further highlights that we are seeing these galaxies near the end of their active formation phase.

Download Full-text