scholarly journals Etching glass in the early Universe: Luminous HF and H2O emission in a QSO-SMG pair at z = 4.7

2020 ◽  
Vol 641 ◽  
pp. A124 ◽  
Author(s):  
M. D. Lehnert ◽  
C. Yang ◽  
B. H. C. Emonts ◽  
A. Omont ◽  
E. Falgarone ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Small Sample ◽  
Continuum Emission ◽  
Absorption Feature ◽  
Bootstrap Analysis ◽  
Molecular Outflows ◽  
Outflow Rate ◽  
Intense Star Formation

We present ALMA observations of hydrogen fluoride, HF J = 1–0, water, H2O (220–211), and the 1.2 THz rest-frame continuum emission from the z = 4.7 system BR 1202-0725. System BR 1202-0725 is a galaxy group consisting of a quasi-stellar object (QSO), a sub-millimeter galaxy (SMG), and a pair of Lyα emitters. We detected HF in emission in the QSO and possibly in absorption in the SMG, while water was detected in emission in both the QSO and the SMG. The QSO is the most luminous HF J = 1–0 emitter that has yet been found and has the same ratio of HF emission-line to infrared luminosity, LHF/LIR, as a small sample of local active galactic nuclei and the Orion Bar. This consistency covers about ten orders of magnitude in LIR. Based on the conclusions of a study of HF emission in the Orion Bar and simple radiative transfer modeling, the HF emission in the QSO is excited either by collisions with electrons (and H2) in molecular plasmas irradiated by the AGN and intense star formation, or predominately by collisions with H2, with a modest contribution from electrons, in a relatively high temperature (∼120 K), dense (∼105 cm−3) medium. The high density of electrons necessary to collisionally excite the HF J = 1–0 line can be supplied in sufficient quantities by the estimated column density of C+. Although HF should be an excellent tracer of molecular outflows, we found no strong kinematic evidence for outflows in HF in either the QSO or the SMG. From a putative absorption feature in HF observed against the continuum emission from the SMG, we conducted a bootstrap analysis to estimate an upper limit on the outflow rate, Ṁoutflow ≲ 45 M⊙ yr−1. This result implies that the ratio of the molecular outflow rate to the star formation rate is Ṁoutflow/SFR ≲ 5% for the SMG. Both the QSO and the SMG are among the most luminous H2O (220–211) emitters currently known and are found to lie along the same relationship between LH2O (220 − 211)/LIR and LIR as a large sample of local and high-redshift star-forming galaxies. The kinematics of the H2O (220–211) line in the SMG is consistent with a rotating disk as found previously but the line profile appears broader than other molecular lines, with a full width at half maximum of ∼1020 km s−1. The broadness of the line, which is similar to the width of a much lower resolution observation of CO(2-1), may suggest that either the gas on large scales (≳4 kpc) is significantly more disturbed and turbulent due either to interactions and mass exchange with the other members of the group, or to the dissipation of the energy of the intense star formation, or both. Overall however, the lack of significant molecular outflows in either source may imply that much of the energy from the intense star formation and active galactic nucleus in this pair is being dissipated in their interstellar media.

scholarly journals Detection of a high-redshift molecular outflow in a primeval hyperstarburst galaxy

2019 ◽  
Vol 632 ◽  
pp. L7 ◽  
Author(s):  
G. C. Jones ◽  
R. Maiolino ◽  
P. Caselli ◽  
S. Carniani
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Host Galaxy ◽  
Starburst Galaxy ◽  
High Excitation ◽  
Star Formation Region ◽  
Molecular Outflow ◽  
Outflow Rate ◽  
Major Merger

We report the discovery of a high-redshift, massive molecular outflow in the starburst galaxy SPT 0346-52 (z = 5.656) via the detected absorption of high-excitation water transitions (H2O 42,3 − 41,4 and H2O 33,0 − 32,1) with the Atacama Large Millimeter/submillimeter Array (ALMA). The host galaxy is one of the most powerful starburst galaxies at high redshift (star formation rate; SFR ∼3600 M⊙ year−1), with an extremely compact (∼320 pc) star formation region and a SFR surface density (ΣSFR ∼ 5500 M⊙ year−1 kpc−2) five times higher than “maximum” (i.e. Eddington-limited) starbursts, implying a highly transient phase. The estimated outflow rate is ∼500 M⊙ year−1, which is much lower than the SFR, implying that in this extreme starburst the outflow capabilities saturate and the outflow is no longer capable of regulating star formation, resulting in a runaway process in which star formation will use up all available gas in less than 30 Myr. Finally, while previous kinematic investigations of this source revealed possible evidence for an ongoing major merger, the coincidence of the hyper-compact starburst and high-excitation water absorption indicates that this is a single starburst galaxy surrounded by a disc.

scholarly journals The importance of nebular emission for SED modeling of distant star-forming galaxies

2011 ◽  
Vol 7 (S284) ◽  
pp. 20-25 ◽  
Author(s):  
Daniel Schaerer ◽  
Stephane de Barros
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Broad Band ◽  
Continuum Emission ◽  
Physical Parameters ◽  
Mass Star ◽  
Star Forming ◽  
The Galaxy ◽  
Dust Attenuation

AbstractWe highlight and discuss the importance of accounting for nebular emission in the SEDs of high redshift galaxies, as lines and continuum emission can contribute significantly or subtly to broad-band photometry. Physical parameters such as the galaxy age, mass, star-formation rate, dust attenuation and others inferred from SED fits can be affected to different extent by the treatment of nebular emission.We analyse a large sample of Lyman break galaxies from z ~ 3–6, and show some main results illustrating e.g. the importance of nebular emission for determinations of the mass–SFR relation, attenuation and age. We suggest that a fairly large scatter in such relations could be intrinsic. We find that the majority of objects (~ 60–70%) is better fit with SEDs accounting for nebular emission; the remaining galaxies are found to show relatively weak or no emission lines. Our modeling, and supporting empirical evidence, suggests the existence of two categories of galaxies, “starbursts” and “post-starbursts” (lower SFR and older galaxies) among the LBG population, and relatively short star-formation timescales.

scholarly journals Quasi-equilibrium models of high-redshift disc galaxy evolution

2020 ◽  
Vol 500 (3) ◽  
pp. 3394-3412
Author(s):  
Steven R Furlanetto
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Formation Rate ◽  
New Physics ◽  
Small Scale ◽  
Quasi Equilibrium ◽  
Mass Relation ◽  
Disc Galaxy

ABSTRACT In recent years, simple models of galaxy formation have been shown to provide reasonably good matches to available data on high-redshift luminosity functions. However, these prescriptions are primarily phenomenological, with only crude connections to the physics of galaxy evolution. Here, we introduce a set of galaxy models that are based on a simple physical framework but incorporate more sophisticated models of feedback, star formation, and other processes. We apply these models to the high-redshift regime, showing that most of the generic predictions of the simplest models remain valid. In particular, the stellar mass–halo mass relation depends almost entirely on the physics of feedback (and is thus independent of the details of small-scale star formation) and the specific star formation rate is a simple multiple of the cosmological accretion rate. We also show that, in contrast, the galaxy’s gas mass is sensitive to the physics of star formation, although the inclusion of feedback-driven star formation laws significantly changes the naive expectations. While these models are far from detailed enough to describe every aspect of galaxy formation, they inform our understanding of galaxy formation by illustrating several generic aspects of that process, and they provide a physically grounded basis for extrapolating predictions to faint galaxies and high redshifts currently out of reach of observations. If observations show violations from these simple trends, they would indicate new physics occurring inside the earliest generations of galaxies.

scholarly journals Radio continuum size evolution of star-forming galaxies over 0.35 < z < 2.25

2019 ◽  
Vol 625 ◽  
pp. A114 ◽  
Author(s):  
E. F. Jiménez-Andrade ◽  
B. Magnelli ◽  
A. Karim ◽  
G. Zamorani ◽  
M. Bondi ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Gaussian Model ◽  
Cosmic Time ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Selection Function ◽  
Star Forming ◽  
Size Evolution ◽  
Galaxy Population

To better constrain the physical mechanisms driving star formation, we present the first systematic study of the radio continuum size evolution of star-forming galaxies (SFGs) over the redshift range 0.35 <  z <  2.25. We use the VLA COSMOS 3 GHz map (noise rms = 2.3 μJy beam−1, θbeam = 0.75 arcsec) to construct a mass-complete sample of 3184 radio-selected SFGs that reside on and above the main sequence (MS) of SFGs. We constrain the overall extent of star formation activity in galaxies by applying a 2D Gaussian model to their radio continuum emission. Extensive Monte Carlo simulations are used to validate the robustness of our measurements and characterize the selection function. We find no clear dependence between the radio size and stellar mass, M⋆, of SFGs with 10.5 ≲ log(M⋆/M⊙) ≲ 11.5. Our analysis suggests that MS galaxies are preferentially extended, while SFGs above the MS are always compact. The median effective radius of SFGs on (above) the MS of Reff = 1.5 ± 0.2 (1.0 ± 0.2) kpc remains nearly constant with cosmic time; a parametrization of the form Reff ∝ (1 + z)α yields a shallow slope of only α = −0.26 ± 0.08 (0.12 ± 0.14) for SFGs on (above) the MS. The size of the stellar component of galaxies is larger than the extent of the radio continuum emission by a factor ∼2 (1.3) at z = 0.5 (2), indicating star formation is enhanced at small radii. The galactic-averaged star formation rate surface density (ΣSFR) scales with the distance to the MS, except for a fraction of MS galaxies (≲10%) that harbor starburst-like ΣSFR. These “hidden” starbursts might have experienced a compaction phase due to disk instability and/or a merger-driven burst of star formation, which may or may not significantly offset a galaxy from the MS. We thus propose to use ΣSFR and distance to the MS in conjunction to better identify the galaxy population undergoing a starbursting phase.

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 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.

Extreme variations in star formation activity in the first galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 226-230
Author(s):  
Christian Binggeli ◽  
Erik Zackrisson ◽  
Xiangcheng Ma ◽  
Akio K. Inoue ◽  
Anton Vikaeus ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
High Redshift ◽  
Formation Rate ◽  
High Redshift Galaxies ◽  
James Webb Space Telescope ◽  
Star Formation Activity ◽  
The Galaxy ◽  
First Galaxies ◽  
Star Formation Histories

AbstractRecently, spectroscopic detections of O[III] 88 μm and Ly-α emission lines from the z ≍ 9.1 galaxy MACS1149-JD1 have been presented, and with these, some interesting properties of this galaxy were uncovered. One such property is that MACS1149-JD1 exhibits a significant Balmer break at around rest-frame 4000 Å, which may indicate that the galaxy has experienced large variations in star formation rate prior to z ∼ 9, with a rather long period of low star formation activity. While some simulations predict large variations in star formation activity in high-redshift galaxies, it is unclear whether the simulations can reproduce the kind of variations seen in MACS1149-JD1. Here, we utilize synthetic spectra of simulated galaxies from two simulation suites in order to study to what extent these can accurately reproduce the spectral features (specifically the Balmer break) observed in MACS1149-JD1. We show that while the simulations used in this study produce galaxies with varying star formation histories, galaxies such as MACS1149-JD1 would be very rare in the simulations. In principle, future observations with the James Webb Space Telescope may tell us if MACS1149-JD1 represents something rare, or if such galaxies are more common than predicted by current simulations.

The impact of star formation sampling effects on the spectra of lensed z > 6 galaxies detectable with JWST

2019 ◽  
Vol 492 (2) ◽  
pp. 1706-1712
Author(s):  
Anton Vikaeus ◽  
Erik Zackrisson ◽  
Christian Binggeli
Keyword(s):  
Star Formation ◽  
Spectral Synthesis ◽  
High Redshift ◽  
Formation Rate ◽  
Mass Function ◽  
Spectroscopic Studies ◽  
Initial Mass Function ◽  
James Webb Space Telescope ◽  
Population Iii Stars ◽  
The Impact

ABSTRACT The upcoming James Webb Space Telescope (JWST) will allow observations of high-redshift galaxies at fainter detection levels than ever before, and JWST surveys targeting gravitationally lensed fields are expected to bring z ≳ 6 objects with very low star formation rate (SFR) within reach of spectroscopic studies. As galaxies at lower and lower star formation activity are brought into view, many of the standard methods used in the analysis of integrated galaxy spectra are at some point bound to break down, due to violation of the assumptions of a well-sampled stellar initial mass function (IMF) and a slowly varying SFR. We argue that galaxies with SFR ∼ 0.1 M⊙ yr−1 are likely to turn up at the spectroscopic detection limit of JWST in lensed fields, and investigate to what extent star formation sampling may affect the spectral analysis of such objects. We use the slug spectral synthesis code to demonstrate that such effects are likely to have significant impacts on spectral diagnostics of, for example, the Balmer emission lines. These effects are found to stem primarily from SFRs varying rapidly on short (∼Myr) time-scales due to star formation in finite units (star clusters), whereas the effects of an undersampled IMF is deemed insignificant in comparison. In contrast, the ratio between the He ii- and H i-ionizing flux is found to be sensitive to IMF-sampling as well as ICMF-sampling (sampling of the initial cluster mass function), which may affect interpretations of galaxies containing Population III stars or other sources of hard ionizing radiation.

scholarly journals Semi-analytic forecasts for JWST – II. Physical properties and scaling relations for galaxies at z = 4–10

2019 ◽  
Vol 490 (2) ◽  
pp. 2855-2879 ◽  
Author(s):  
L Y Aaron Yung ◽  
Rachel S Somerville ◽  
Gergö Popping ◽  
Steven L Finkelstein ◽  
Harry C Ferguson ◽  
...  
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
High Redshift ◽  
Formation Rate ◽  
Distribution Functions ◽  
Scaling Relations ◽  
Physical Parameters ◽  
Model Parameters ◽  
Galaxy Populations ◽  
The Impact

ABSTRACT The long anticipated James Webb Space Telescope (JWST) will be able to directly detect large samples of galaxies at very high redshift. Using the well-established, computationally efficient Santa Cruz semi-analytic model, with recently implemented multiphase gas partitioning, and H2-based star formation recipes, we make predictions for a wide variety of galaxy properties for galaxy populations at z = 4–10. In this work, we provide forecasts for the physical properties of high-redshift galaxies and links to their photometric properties. With physical parameters calibrated only to z ∼ 0 observations, our model predictions are in good agreement with current observational constraints on stellar mass and star formation rate distribution functions up to z ∼ 8. We also provide predictions representing wide, deep, and lensed JWST survey configurations. We study the redshift evolution of key galaxy properties and the scaling relations among them. Taking advantage of our models’ high computational efficiency, we study the impact of systematically varying the model parameters. All distribution functions and scaling relations presented in this work are available at https://www.simonsfoundation.org/semi-analytic-forecasts-for-jwst/.

scholarly journals The effects of population III radiation backgrounds on the cosmological 21-cm signal

2020 ◽  
Vol 493 (1) ◽  
pp. 1217-1226 ◽  
Author(s):  
Richard H Mebane ◽  
Jordan Mirocha ◽  
Steven R Furlanetto
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
Radio Emission ◽  
Formation Rate ◽  
Fine Tuning ◽  
Absorption Feature ◽  
Simulation Code ◽  
X Ray ◽  
Neutral Gas ◽  
Population Iii

ABSTRACT We investigate the effects of Population III (Pop III) stars and their remnants on the cosmological 21-cm global signal. By combining a semi-analytic model of Pop III star formation with a global 21-cm simulation code, we investigate how X-ray and radio emission from accreting Pop III black holes may affect both the timing and depth of the 21-cm absorption feature that follows the initial onset of star formation during the Cosmic Dawn. We compare our results to the findings of the EDGES experiment, which has reported the first detection of a cosmic 21-cm signal. In general, we find that our fiducial Pop III models, which have peak star formation rate densities of ∼10−4 M⊙ yr−1 Mpc−3 between z ∼ 10 and z ∼ 15, are able to match the timing of the EDGES signal quite well, in contrast to models that ignore Pop III stars. To match the unexpectedly large depth of the EDGES signal without recourse to exotic physics, we vary the parameters of emission from accreting black holes (formed as Pop III remnants) including the intrinsic strength of X-ray and radio emission as well as the local column density of neutral gas. We find that models with strong radio emission and relatively weak X-ray emission can self-consistently match the EDGES signal, though this solution requires fine-tuning. We are only able to produce signals with sharp features similar to the EDGES signal if the Pop III IMF is peaked narrowly around $140 \, \mathrm{M}_\odot$.

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