scholarly journals Complete Ionisation of the Neutral Gas in High Redshift Radio Galaxies and Quasars

2012 ◽  
Vol 8 (S292) ◽  
pp. 243-243
Author(s):  
S. J. Curran ◽  
M. T. Whiting
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Ultra Violet ◽  
Radio Galaxies ◽  
Raw Material ◽  
Optical Photometry ◽  
Star Forming ◽  
Neutral Gas ◽  
Luminous Objects ◽  
Selection Of

AbstractCool neutral gas provides the raw material for all star formation in the Universe, and yet, from a survey of the hosts of high redshift radio galaxies and quasars, we find a complete dearth of atomic (Hi 21-cm) and molecular (OH, CO, HCO+ & HCN) absorption at redshifts z ≳ 3 (Curran et al. 2008). Upon a thorough analysis of the optical photometry, we find that all of our targets have ionising (λ ≤ 912 Å) ultra-violet continuum luminosities of LUV ≳ 1023 W Hz−1. We therefore attribute this deficit to the traditional optical selection of targets biasing surveys towards the most ultra-violet luminous objects, where the intense radiation excites the neutral gas to the point where it cannot engage in star formation (Curran & Whiting 2010). However, this hypothesis does not explain why there is a critical luminosity, rather than a continuum where the detections gradually become fewer and fewer as the harshness of the radiation increases. We show that by placing a quasar within a galaxy of gas there is always a finite ultra-violet luminosity above which all of the gas is ionised. This demonstrates that these galaxies are probably devoid of star-forming material rather than this being at abundances below the sensitivity limits of current radio telescopes.

scholarly journals Neutral Gas and Metals From z = 4 to z = 0.5

2006 ◽  
Vol 2 (S235) ◽  
pp. 273-274
Author(s):  
Céline Péroux
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
High Redshift ◽  
Formation Rate ◽  
High Redshift Galaxies ◽  
Complementary Method ◽  
Neutral Gas ◽  
History Of ◽  
The Universe ◽  
Selection Of

AbstractA complementary method to the emission selection of high-redshift galaxies consists in the observation of absorbers along the line of sight toward a background quasar. This selection technique has a constant sensitivity at all redshifts up to z = 6 (i.e. no redshift desert) and allow to select all types of galaxies regardless of their luminosity or star formation rate. The highest column density absorbers, the Damped Lyman-α (DLAs) systems, in particular, can be used to determine the cosmic evolution of HI gas in the Universe, ΩHI, and the global metallicity in the gas phase. Since stars are known to form from HI gas, ΩHI provides an indirect tracer of the history of star formation. Recent results from several parallel VLT programmes aiming at determining the cosmological evolution of the metallicity in the neutral gas phase are presented.

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

2007 ◽  
Vol 375 (4) ◽  
pp. 1299-1310 ◽  
Author(s):  
M. Villar-Martín ◽  
A. Humphrey ◽  
C. De Breuck ◽  
R. Fosbury ◽  
L. Binette ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Radio Galaxies

scholarly journals Exploration of the high-redshift universe enabled by THESEUS

2021 ◽  
Author(s):  
N. R. Tanvir ◽  
E. Le Floc’h ◽  
L. Christensen ◽  
J. Caruana ◽  
R. Salvaterra ◽  
...  
Keyword(s):  
Star Formation ◽  
Gamma Ray ◽  
High Redshift ◽  
Formation Rate ◽  
Star Forming ◽  
Chemical Enrichment ◽  
Long Duration ◽  
Absorption Studies ◽  
Population Iii Stars ◽  
High Redshift Universe

AbstractAt peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer of star formation and star-forming galaxies over the whole of cosmic history. Their bright power-law afterglows provide ideal backlights for absorption studies of the interstellar and intergalactic medium back to the reionization era. The proposed THESEUS mission is designed to detect large samples of GRBs at z > 6 in the 2030s, at a time when supporting observations with major next generation facilities will be possible, thus enabling a range of transformative science. THESEUS will allow us to explore the faint end of the luminosity function of galaxies and the star formation rate density to high redshifts; constrain the progress of re-ionisation beyond $z\gtrsim 6$ z ≳ 6 ; study in detail early chemical enrichment from stellar explosions, including signatures of Population III stars; and potentially characterize the dark energy equation of state at the highest redshifts.

scholarly journals Planck’s dusty GEMS

2018 ◽  
Vol 620 ◽  
pp. A60 ◽  
Author(s):  
R. Cañameras ◽  
N. P. H. Nesvadba ◽  
M. Limousin ◽  
H. Dole ◽  
R. Kneissl ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Infrared Imaging ◽  
High Redshift ◽  
Dust Emission ◽  
Galaxy Cluster ◽  
Star Forming ◽  
The Galaxy ◽  
Mass Outflow ◽  
Gas Accretion

We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few 109 M⊙, in the strongly gravitationally lensed submillimeter galaxy “the Emerald” (PLCK_G165.7+49.0) at z = 2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5″ and 21″ formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z = 0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4–3) line and 850 μm dust emission to characterize the foreground lensing mass distribution, construct a lens model with LENSTOOL, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a 9 × 1010 M⊙, fragmented disk with 20% gas fraction. The stellar continuum morphology is much smoother and also well resolved perpendicular to the magnification axis. One of the clumps shows a pronounced blue wing in the CO(4–3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of –200 km s−1 is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.

scholarly journals The influence of a top-heavy integrated galactic IMF and dust on the chemical evolution of high-redshift starbursts

2020 ◽  
Vol 494 (2) ◽  
pp. 2355-2373 ◽  
Author(s):  
M Palla ◽  
F Calura ◽  
F Matteucci ◽  
X L Fan ◽  
F Vincenzo ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Chemical Elements ◽  
High Redshift ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Strong Impact ◽  
Star Forming ◽  
Abundance Patterns

ABSTRACT We study the effects of the integrated galactic initial mass function (IGIMF) and dust evolution on the abundance patterns of high redshift starburst galaxies. In our chemical models, the rapid collapse of gas clouds triggers an intense and rapid star formation episode, which lasts until the onset of a galactic wind, powered by the thermal energy injected by stellar winds and supernova explosions. Our models follow the evolution of several chemical elements (C, N, α-elements, and Fe) both in the gas and dust phases. We test different values of β, the slope of the embedded cluster mass function for the IGIMF, where lower β values imply a more top-heavy initial mass function (IMF). The computed abundances are compared to high-quality abundance measurements obtained in lensed galaxies and from composite spectra in large samples of star-forming galaxies in the redshift range 2 ≲ z ≲ 3. The adoption of the IGIMF causes a sensible increase of the rate of star formation with respect to a standard Salpeter IMF, with a strong impact on chemical evolution. We find that in order to reproduce the observed abundance patterns in these galaxies, either we need a very top-heavy IGIMF (β < 2) or large amounts of dust. In particular, if dust is important, the IGIMF should have β ≥ 2, which means an IMF slightly more top-heavy than the Salpeter one. The evolution of the dust mass with time for galaxies of different mass and IMF is also computed, highlighting that the dust amount increases with a top-heavier IGIMF.

scholarly journals Observations of the Lyman-α Universe

2020 ◽  
Vol 58 (1) ◽  
pp. 617-659
Author(s):  
Masami Ouchi ◽  
Yoshiaki Ono ◽  
Takatoshi Shibuya
Keyword(s):  
Star Formation ◽  
Dwarf Galaxy ◽  
High Redshift ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Resonant Scattering ◽  
Dark Matter Halo ◽  
Emission Data ◽  
Star Forming ◽  
High Redshift Universe

Hydrogen Lyman-α (Lyα) emission has been one of the major observational probes for the high-redshift Universe since the first discoveries of high- z Lyα-emitting galaxies in the late 1990s. Due to the strong Lyα emission originated by resonant scattering and recombination of the most abundant element, Lyα observations witness not only Hii regions of star formation and active galactic nuclei (AGNs) but also diffuse Hi gas in the circumgalactic medium (CGM) and the intergalactic medium (IGM). Here, we review Lyα sources and present theoretical interpretations reached to date. We conclude the following: ▪  A typical Lyα emitter (LAE) at z ≳ 2 with a L* Lyα luminosity is a high- z counterpart of a local dwarf galaxy, a compact metal-poor star-forming galaxy (SFG) with an approximate stellar (dark matter halo) mass and star-formation rate of 108−9M⊙ (1010−11M⊙) and 1–10 M⊙ year−1, respectively. ▪  High- z SFGs ubiquitously have a diffuse Lyα-emitting halo in the CGM extending to the halo virial radius and beyond. ▪  Remaining neutral hydrogen at the epoch of cosmic reionization makes a strong dimming of Lyα emission for galaxies at z > 6 that suggests the late reionization history. The next-generation large-telescope projects will combine Lyα emission data with Hi Lyα absorptions and 21-cm radio data that map out the majority of hydrogen (Hi+Hii) gas, uncovering the exchanges of ( a) matter by outflow and inflow and ( b) radiation, relevant to cosmic reionization, between galaxies and the CGM/IGM.

scholarly journals LoTSS/HETDEX: Disentangling star formation and AGN activity in gravitationally lensed radio-quiet quasars

2019 ◽  
Vol 622 ◽  
pp. A18
Author(s):  
H. R. Stacey ◽  
J. P. McKean ◽  
N. J. Jackson ◽  
P. N. Best ◽  
G. Calistro Rivera ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Far Infrared ◽  
Full Data ◽  
Star Forming ◽  
Black Hole Accretion ◽  
Sky Survey ◽  
Future Data ◽  
Frequency Window ◽  
Hole Accretion

Determining the star-forming properties of radio-quiet quasars is important for understanding the co-evolution of star formation and black hole accretion. We present the detection of the gravitationally lensed radio-quiet quasars SDSS J1055+4628, SDSS J1313+5151, and SBS 1520+530 at 144 MHz, which fall in the HETDEX Spring Field targeted in the LOFAR Two-metre Sky Survey (LoTSS) first full data release. We compare their radio and far-infrared luminosities relative to the radio–infrared correlation and find that their radio luminosities can be explained by star formation. The implied star formation rates derived from their radio and infrared luminosities are between 20 and 300 M ⊙ yr−1. These detections represent the first study of gravitationally lensed sources with LOFAR, opening a new frequency window for investigating the star-forming properties of high-redshift quasars at radio wavelengths. We consider the implications for future data releases and estimate that many of the objects in our parent sample will be detected during LoTSS, significantly increasing the fraction of gravitationally lensed radio-quiet quasars with radio detections.

scholarly journals Dusty magnetohydrodynamics in star-forming regions

2010 ◽  
Vol 76 (3-4) ◽  
pp. 569-578
Author(s):  
S. VAN LOO ◽  
S. A. E. G. FALLE ◽  
T. W. HARTQUIST ◽  
O. HAVNES ◽  
G. E. MORFILL
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Number Density ◽  
Star Forming ◽  
Star Forming Regions ◽  
Neutral Gas ◽  
Gas Phase Ions ◽  
Fractional Ionization ◽  
Magnetohydrodynamic Models ◽  
The Magnetic Field

AbstractStar formation occurs in dark molecular regions where the number density of hydrogen nuclei nH exceeds 104 cm−3 and the fractional ionization is 10−7 or less. Dust grains with sizes ranging up to tenths of microns and perhaps down to tens of nanometers contain just less than 1% of the mass. Recombination on grains is important for the removal of gas-phase ions, which are produced by cosmic rays penetrating the dark regions. Collisions of neutrals with charged grains contribute significantly to the coupling of the magnetic field to the neutral gas. Consequently, the dynamics of the grains must be included in the magnetohydrodynamic models of large-scale collapse, the evolution of waves and the structures of shocks important in star formation.

scholarly journals The star formation process in the Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 191-202
Author(s):  
J. M. Oliveira
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Critical Density ◽  
Mass Function ◽  
Magellanic Clouds ◽  
Initial Mass Function ◽  
Star Forming ◽  
Bridge Span ◽  
Individual Star ◽  
Low Metallicity

AbstractThe Magellanic Clouds offer unique opportunities to study star formation both on the global scales of an interacting system of gas-rich galaxies, as well as on the scales of individual star-forming clouds. The interstellar media of the Small and Large Magellanic Clouds and their connecting bridge, span a range in (low) metallicities and gas density. This allows us to study star formation near the critical density and gain an understanding of how tidal dwarfs might form; the low metallicity of the SMC in particular is typical of galaxies during the early phases of their assembly, and studies of star formation in the SMC provide a stepping stone to understand star formation at high redshift where these processes can not be directly observed. In this review, I introduce the different environments encountered in the Magellanic System and compare these with the Schmidt-Kennicutt law and the predicted efficiencies of various chemo-physical processes. I then concentrate on three aspects that are of particular importance: the chemistry of the embedded stages of star formation, the Initial Mass Function, and feedback effects from massive stars and its ability to trigger further star formation.

scholarly journals The Evolution of Luminous Compact Blue Galaxies: Disks or Spheroids?

2010 ◽  
Vol 6 (S277) ◽  
pp. 291-295
Author(s):  
D. J. Pisano ◽  
K. Rabidoux ◽  
C. A. Garland ◽  
R. Guzmán ◽  
F. J. Castander ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
High Surface ◽  
Blue Color ◽  
Dynamical Mass ◽  
Star Forming ◽  
Blue Galaxies ◽  
Multi Wavelength ◽  
Fisher Relation ◽  
Combined Data

AbstractLuminous compact blue galaxies (LCBGs) are a diverse class of galaxies characterized by high luminosity, blue color, and high surface brightness that sit at the critical juncture of galaxies evolving from the blue to the red sequence. As part of our multi-wavelength survey of local LCBGs, we have been studying the HI content of these galaxies using both single-dish telescopes and interferometers. Our goals are to determine if single-dish HI observations represent a true measure of the dynamical mass of LCBGs and to look for signatures of recent interactions that may be triggering star formation in LCBGs. Our data show that while some LCBGs are undergoing interactions, many appear isolated. While all LCBGs contain HI and show signatures of rotation, the population does not lie on the Tully-Fisher relation nor can it evolve onto it. Furthermore, the HI maps of many LCBGs show signatures of dynamically hot components, suggesting that we are seeing the formation of a thick disk or spheroid in at least some LCBGs. There is good agreement between the HI and Hα kinematics for LCBGs, and both are similar in appearance to the Hα kinematics of high redshift star-forming galaxies. Our combined data suggest that star formation in LCBGs is primarily quenched by virial heating, consistent with model predictions.

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