Disk Galaxies at High Redshift?

AbstractThe successful implementation of integral field near-infrared spectrographs fed by adaptive optics is providing unprecedented views of gas motions within galaxies at redshifts z = 2 − 3, when the universe was forming stars at its peak rate. A complex picture of galaxy kinematics is emerging, with inflows, rotation within sometimes extended and nearly always thick disks, mergers, and galaxy-wide outflows all contributing to the variety of patterns seen. On the computational side, simulations of galaxy formation have reached a level of sophistication which can not only reproduce many of the properties of today's galaxies, but also throws new light on high redshift galaxies which are too faint to be detected directly, such as those giving rise to quasar absorption lines. In this brief review, I summarise recent progress in these areas.

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New methods for identifying Lyman continuum leakers and reionization-epoch analogues

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2355 ◽

2020 ◽

Vol 498 (1) ◽

pp. 164-180 ◽

Cited By ~ 2

Author(s):

Harley Katz ◽

Dominika Ďurovčíková ◽

Taysun Kimm ◽

Joki Rosdahl ◽

Jeremy Blaizot ◽

...

Keyword(s):

Emission Line ◽

Galaxy Formation ◽

Dwarf Galaxy ◽

High Redshift ◽

Indirect Methods ◽

High Redshift Galaxies ◽

Lyman Continuum ◽

The Universe ◽

Ionization Parameter ◽

Redshift Galaxies

ABSTRACT Identifying low-redshift galaxies that emit Lyman continuum radiation (LyC leakers) is one of the primary, indirect methods of studying galaxy formation in the epoch of reionization. However, not only has it proved challenging to identify such systems, it also remains uncertain whether the low-redshift LyC leakers are truly ‘analogues’ of the sources that reionized the Universe. Here, we use high-resolution cosmological radiation hydrodynamics simulations to examine whether simulated galaxies in the epoch of reionization share similar emission line properties to observed LyC leakers at z ∼ 3 and z ∼ 0. We find that the simulated galaxies with high LyC escape fractions (fesc) often exhibit high O32 and populate the same regions of the R23–O32 plane as z ∼ 3 LyC leakers. However, we show that viewing angle, metallicity, and ionization parameter can all impact where a galaxy resides on the O32–fesc plane. Based on emission line diagnostics and how they correlate with fesc, lower metallicity LyC leakers at z ∼ 3 appear to be good analogues of reionization-era galaxies. In contrast, local [S ii]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the S ii Baldwin–Phillips–Terlevich (BPT) diagram; however, this diagnostic may still be useful for identifying leakers. We use our simulated galaxies to develop multiple new diagnostics to identify LyC leakers using infrared and nebular emission lines. We show that our model using only [C ii]158 μm and [O iii]88 μm can identify potential leakers from non-leakers from the local Dwarf Galaxy Survey. Finally, we apply this diagnostic to known high-redshift galaxies and find that MACS 1149_JD1 at z = 9.1 is the most likely galaxy to be actively contributing to the reionization of the Universe.

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Diffraction Limited Imaging of High Redshift Galaxies with Adaptive Optics

Symposium - International Astronomical Union ◽

10.1017/s007418090022175x ◽

2001 ◽

Vol 205 ◽

pp. 455-456 ◽

Cited By ~ 1

Author(s):

R.I. Davies ◽

M. Lehnert ◽

A.J. Baker ◽

S. Rabien

Keyword(s):

Adaptive Optics ◽

Near Infrared ◽

High Redshift ◽

Diffraction Limit ◽

High Redshift Galaxies ◽

Distant Galaxies ◽

Imaging And Spectroscopy ◽

Intermediate Redshift ◽

Initial Results ◽

Redshift Galaxies

The major cornerstone of future ground-based astronomy is imaging and spectroscopy at the diffraction limit using adaptive optics. To exploit the potential of current AO systems, we have begun a survey around bright stars to study intermediate redshift galaxies at high resolution. Using ALFA to reach the diffraction limit of the 3.5-m telescope at Calar Alto allows us to study the structure of distant galaxies in the near-infrared at scales of 100-150 pc for z=0.05 and at scales 1.0-1.5 kpc at z=1. In this contribution we present the initial results of this project, which hint at the exciting prospects possible with the resolution and sensitivity available using an AO camera on the 8-m class VLT.

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13C/18O ratio as a litmus test of stellar IMF variations in high-redshift starbursts

Proceedings of the International Astronomical Union ◽

10.1017/s174392131900886x ◽

2019 ◽

Vol 15 (S352) ◽

pp. 234-238

Author(s):

Donatella Romano ◽

Zhi-Yu Zhang ◽

Francesca Matteucci ◽

Rob J. Ivison ◽

Padelis P. Papadopoulos

Keyword(s):

Galaxy Formation ◽

High Redshift ◽

Indirect Evidence ◽

Direct Methods ◽

Mass Function ◽

Initial Mass Function ◽

High Mass ◽

Theoretical Ground ◽

Litmus Test ◽

The Universe

AbstractDetermining the shape of the stellar initial mass function (IMF) and whether it is constant or varies in space and time is the Holy Grail of modern astrophysics, with profound implications for all theories of star and galaxy formation. On a theoretical ground, the extreme conditions for star formation (SF) encountered in the most powerful starbursts in the Universe are expected to favour the formation of massive stars. Direct methods of IMF determination, however, cannot probe such systems, because of the severe dust obscuration affecting their starlight. The next best option is to observe CNO bearing molecules in the interstellar medium at millimetre/ submillimetre wavelengths, which, in principle, provides the best indirect evidence for IMF variations. In this contribution, we present our recent findings on this issue. First, we reassess the roles of different types of stars in the production of CNO isotopes. Then, we calibrate a proprietary chemical evolution code using Milky Way data from the literature, and extend it to discuss extragalactic data. We show that, though significant uncertainties still hamper our knowledge of the evolution of CNO isotopes in galaxies, compelling evidence for an IMF skewed towards high-mass stars can be found for galaxy-wide starbursts. In particular, we analyse a sample of submillimetre galaxies observed by us with the Atacama Large Millimetre Array at the peak of the SF activity of the Universe, for which we measure 13C/18O⋍1. This isotope ratio is especially sensitive to IMF variations, and is little affected by observational uncertainties. At the end, ongoing developments of our work are briefly outlined.

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Theoretically modelling photoionised regions with fractal geometry in three-dimension

Proceedings of the International Astronomical Union ◽

10.1017/s174392131900841x ◽

2019 ◽

Vol 15 (S352) ◽

pp. 71-72

Author(s):

Yifei Jin ◽

Lisa Kewley ◽

Ralph Sutherland

Keyword(s):

Monte Carlo ◽

Emission Line ◽

Galaxy Formation ◽

Fractal Geometry ◽

Complex Geometry ◽

High Redshift ◽

Three Dimension ◽

High Redshift Galaxies ◽

Monte Carlo Techniques ◽

Galaxy Formation And Evolution

AbstractAccurate predictions of the physics of interstellar medium (ISM) are vital for understanding galaxy formation and evolution. Modelling photoionized regions with complex geometry produces realistic ionization structures within the nebulae, providing the necessary physical predictions to interpret observational data. 3D photoionization codes built with Monte Carlo techniques provide powerful tools to produce the ionizing radiation field with fractal geometry. We present a high-resolution Monte Carlo modelling of a nebula with fractal geometry, and will further show how nebular geometry influences the emission-line behaviours. Our research has important implications for studies of emission-line ratios in high redshift galaxies.

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The potential of using KMOS for multi-object massive star spectroscopy

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317001326 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 454-454

Author(s):

Michael Wegner ◽

Ralf Bender ◽

Ray Sharples ◽

Keyword(s):

Galaxy Formation ◽

Near Infrared ◽

High Redshift ◽

High Mass ◽

Galactic Centre ◽

Star Forming ◽

Star Forming Regions ◽

Spectral Bands ◽

Galaxy Formation And Evolution ◽

Potential Applications

AbstractKMOS, the “K-Band Multi-Object Spectrometer”, was built by a British-German consortium as a second generation instrument for the ESO Paranal Observatory. It is available to the user community since its successful commissioning in 2013 (Sharples et al. 2013). As a multi-object integral field spectrometer for the near infrared, KMOS offers 24 deployable IFUs of 2.8x2.8 arcsec and 14x14 spatial pixels each, which can either be placed individually within a 7.2 arcmin field of view or combined in a Mosaic mode in order to map contiguous fields on sky. The instrument covers the whole range of NIR atmospheric windows (0.8. . .2.5μm) with 5 spectral bands and a resolution of R ≈ 3000. . .4000.Although the main science driver for KMOS was to enable the study of galaxy formation and evolution through multiplexed observations of high-redshift galaxies, KMOS also already exhibited its tremendous potential for the spectroscopy of massive stars: A quantitative study of 27 RSGs in NGC 300 (Gazak et al. 2015) proves its applicability for the spectroscopy of individual stars even beyond the Local Group. A Mosaic observation of the Galactic centre (Feldmeier-Krause et al. 2015) demonstrates how spectra of early-type stars can be extracted from a contiguous field. Other applications include (but need not be limited to) velocity determinations of globular cluster stars, observations of jets/outflows of high mass protostars, or contiguous mapping of star-forming regions.We therefore aim at presenting the excellent capabilities of KMOS to a wider community and indicate potential applications.

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Constraining Galaxy Formation Epoch

Symposium - International Astronomical Union ◽

10.1017/s0074180900217026 ◽

2005 ◽

Vol 201 ◽

pp. 536-537

Author(s):

Sukyoung. Yi ◽

T. Brown ◽

S. Heap ◽

I. Hubeny ◽

W. Landsman ◽

...

Keyword(s):

Galaxy Formation ◽

High Redshift ◽

Population Synthesis ◽

High Redshift Galaxies ◽

The Galaxy ◽

The Difference ◽

Age Estimates ◽

Good Agreement ◽

Redshift Galaxies

Pinning down the ages of high redshift galaxies is the most direct way of constraining the galaxy formation epoch. There has been a debate on the age of LBDS 53W091, a red galaxy at z=1.5. The discrepancy in the age estimates of various groups is due to the difference in the population synthesis model. However, there is generally a good agreement among popular models. Polishing the models and assessing their internal uncertainties are crucial in the analysis of high redshift galaxies.

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Near‐Infrared Adaptive Optics Imaging of High‐Redshift Quasars

The Astrophysical Journal ◽

10.1086/524839 ◽

2008 ◽

Vol 673 (2) ◽

pp. 694-702 ◽

Cited By ~ 24

Author(s):

Renato Falomo ◽

Aldo Treves ◽

Jari K. Kotilainen ◽

Riccardo Scarpa ◽

Michela Uslenghi

Keyword(s):

Adaptive Optics ◽

Near Infrared ◽

High Redshift ◽

Adaptive Optics Imaging

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Dark-ages reionization and galaxy formation simulation – XVII. Sizes, angular momenta, and morphologies of high-redshift galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1810 ◽

2019 ◽

Vol 488 (2) ◽

pp. 1941-1959 ◽

Cited By ~ 2

Author(s):

Madeline A Marshall ◽

Simon J Mutch ◽

Yuxiang Qin ◽

Gregory B Poole ◽

J Stuart B Wyithe

Keyword(s):

Angular Momentum ◽

Galaxy Evolution ◽

Galaxy Formation ◽

High Redshift ◽

Stellar Mass ◽

Galaxy Mergers ◽

High Redshift Galaxies ◽

Massive Galaxies ◽

Angular Momenta ◽

Redshift Galaxies

Abstract We study the sizes, angular momenta, and morphologies of high-redshift galaxies, using an update of the meraxes semi-analytic galaxy evolution model. Our model successfully reproduces a range of observations from redshifts z = 0–10. We find that the effective radius of a galaxy disc scales with ultraviolet (UV) luminosity as $R_\mathrm{ e}\propto L_{\textrm{UV}}^{0.33}$ at z = 5–10, and with stellar mass as $R_e\propto M_\ast ^{0.24}$ at z = 5 but with a slope that increases at higher redshifts. Our model predicts that the median galaxy size scales with redshift as Re ∝ (1 + z)−m, where m = 1.98 ± 0.07 for galaxies with (0.3–1)$L^\ast _{z=3}$ and m = 2.15 ± 0.05 for galaxies with (0.12–0.3)$L^\ast _{z=3}$. We find that the ratio between stellar and halo specific angular momentum is typically less than 1 and decreases with halo and stellar mass. This relation shows no redshift dependence, while the relation between specific angular momentum and stellar mass decreases by ∼0.5 dex from z = 7 to z = 2. Our model reproduces the distribution of local galaxy morphologies, with bulges formed predominantly through galaxy mergers for low-mass galaxies, disc-instabilities for galaxies with M* ≃ 1010–$10^{11.5}\, \mathrm{M}_\odot$, and major mergers for the most massive galaxies. At high redshifts, we find galaxy morphologies that are predominantly bulge-dominated.

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Metallicity Evolution of Damped Lyman-α Systems

Symposium - International Astronomical Union ◽

10.1017/s0074180900226223 ◽

2001 ◽

Vol 204 ◽

pp. 307-321

Author(s):

Sandra Savaglio

Keyword(s):

Metal Content ◽

Column Density ◽

High Redshift ◽

Heavy Elements ◽

Gas Content ◽

High Redshift Galaxies ◽

The Galaxy ◽

The Universe ◽

Ism Dust ◽

General Method

According to Pei, Fall, & Hauser (1999), the global metallicity evolution of the Universe can be represented by the ratio of the total metal content to the total gas content measured in damped Lyman–α (DLA) systems (the “column density weighted metallicity” à la Pettini). To minimize dust obscuration effects, a DLA sample with negligible dust content is considered, namely, 50 DLAs with log NHI < 20.8. The global metallicity found shows clear evidence of redshift evolution that goes from ~ 1/30 solar at z ~ 4.1 to solar at z ~ 0.4. More generally, DLAs with measured heavy elements probe the ISM of high redshift galaxies. The whole sample collected from the literature contains 75 DLAs. The metallicity is calculated adopting for the dust correction the most general method used so far, based on models of the ISM dust depletions in the Galaxy. The intrinsic metallicity evolution of DLA galaxies is d log ZDLA/dz = −0.33 ± 0.06.

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