# What is the highest redshift a galaxy with a known stellar mass can be observed?

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As part of my research, I would need the following information which it seems I cannot find it in literature. I would like to know what are the highest redshifts at which $$10^{7}$$, $$10^{8}$$, and $$10^{9}$$ $$[Solar Unit]$$ galaxies can be observed let's say by current HST?

## What is the highest redshift a galaxy with a known stellar mass can be observed? - Astronomy

We present and analyze deep ROSAT observations of two fields containing the most distant (z > 0.7) optically selected clusters of galaxies currently known. We reliably detect X-ray emission from two clusters (including one at z

0.9) out of five with available redshifts, but we do not detect any emission from a further five candidates without spectroscopic data. Although our distant clusters are expected to be among the richest found optically, their X-ray luminosities (L_x_

10^44^ h_50_^-2^ ergs s^-1^) are much lower than those of present-day rich clusters. We argue that the clusters we have detected are the only X-ray-luminous examples in the fields surveyed. By considering the likely volume sampled we find evidence for a decline in the comoving number density of clusters to z

1. On the basis of our current small sample, our results are inconsistent with standard hierarchical clustering models in which the gas evolves in a self-similar fashion, indicating that radiative and hydrodynamic processes may be required to account for the low observed luminosities. For example, a cold dark matter model in which the entropy of the intracluster gas is assumed constant predicts a low abundance of luminous clusters at z

## What is the highest redshift a galaxy with a known stellar mass can be observed? - Astronomy

We present a semi-analytical model of high redshift galaxy formation. In our model the star formation inside a galaxy is regulated by the feedback from supernova (SNe) driven outflows. We derive a closed analytical form for star formation rate in a single galaxy taking account of the SNe feedback in a self-consistent manner. We show that our model can explain the observed correlation between the stellar mass and the circular velocity of galaxies from dwarf galaxies to massive galaxies of 10 12 M ☉ . For small mass dwarf galaxies additional feedback other than supernova feedback is needed to explain the spread in the observational data. Our models reproduce the observed 3-D fundamental correlation between the stellar mass, gas phase metallicity and star formation rate in galaxies establishing that the SNe feedback plays a major role in building this relation. Further, the observed UV luminosity functions of Lyman-Break Galaxies (LBGs) are well explained by our feedback induced star formation model for a vast redshift range of 1.5⩽z⩽8. In particular, the flattening of the luminosity functions at the low luminosity end naturally arises due to our explicit SNe feedback treatment.

## Title: HIGHEST REDSHIFT IMAGE OF NEUTRAL HYDROGEN IN EMISSION: A CHILES DETECTION OF A STARBURSTING GALAXY AT z = 0.376

Our current understanding of galaxy evolution still has many uncertainties associated with the details of the accretion, processing, and removal of gas across cosmic time. The next generation of radio telescopes will image the neutral hydrogen (H i) in galaxies over large volumes at high redshifts, which will provide key insights into these processes. We are conducting the COSMOS H i Large Extragalactic Survey (CHILES) with the Karl G. Jansky Very Large Array, which is the first survey to simultaneously observe H i from z = 0 to z ∼ 0.5. Here, we report the highest redshift H i 21 cm detection in emission to date of the luminous infrared galaxy COSMOS J100054.83+023126.2 at z = 0.376 with the first 178 hr of CHILES data. The total H i mass is (2.9 ± 1.0) × 10 M and the spatial distribution is asymmetric and extends beyond the galaxy. While optically the galaxy looks undisturbed, the H i distribution suggests an interaction with a candidate companion. In addition, we present follow-up Large Millimeter Telescope CO observations that show it is rich in molecular hydrogen, with a range of possible masses of (1.8–9.9) × 10 M .more » This is the first study of the H i and CO in emission for a single galaxy beyond z ∼ 0.2. « less

## Researchers investigate the brightest cluster galaxy in MACS 1931.8-2635

Credit: CC0 Public Domain

Using Very Large Telescope (VLT) and Atacama Large Millimeter/submillimeter Array (ALMA), researchers from the University of Vienna, Austria, and elsewhere have investigated the brightest cluster galaxy (BCG) in a massive galaxy cluster known as MACS 1931.8-2635. Results of the study, published January 28 on arXiv.org, deliver important information about the nature of this BCG.

Galaxy clusters consist of up to thousands of galaxies bound together by gravity. They are the largest gravitationally bound structures, and could therefore be crucial in improving the knowledge about large-scale structure formation and evolution of the universe.

BCGs are generally the brightest galaxies in clusters of galaxies. Observations show that they are mostly massive elliptical galaxies lying close to the geometric and kinematical center of their host galaxy cluster.

At a redshift of approximately 0.35, MACS 1931.8-2635 (M1931 for short) is a massive, X-ray luminous, cool-core galaxy cluster. Its BCG has a stellar mass of about 590 billion solar masses and its star formation rate (SFR) is estimated to be relatively high—some studies point out to a level of some 250 solar masses per year.

Previous studies have found that M1931 BCG harbors one of the most X-ray luminous cool cores yet discovered, with an equivalent mass cooling rate of about 165 solar masses per year. It has also one of the largest known reservoirs of cold gas in a cluster core, with a mass of around 19 billion solar masses, as well as large amounts of dust, with several dust clumps having temperatures less than 10 K.

All in all, M1931 BCG is an example of a cluster with a rapidly cooling core and powerful active galactic nucleus (AGN) feedback and is probably transitioning between two dominant modes of fueling for star formation and feedback. In order to get more insights into the nature and evolution of this BCG, a team of astronomers led by Bianca-Iulia Ciocan of the University of Vienna conducted multiwavelength observations of this galaxy using VLT's Multi Unit Spectroscopic Explorer (MUSE) and ALMA.

"Based on VLT-MUSE optical integral field spectroscopy, we investigated the BCG of the massive cool-core CLASH cluster MACS 1931.8-2635 at a redshift of z=0.35, concerning its spatially resolved star formation activity, ionisation sources, chemical abundances, gas and stellar kinematics. The optical MUSE IFS data is supplemented by sub-mm ALMA observations, allowing us to link the properties of the warm ionised gas to those of the cold molecular gas component," the researchers wrote in the paper.

The study identified ionizing sources in different regions of M1931 BCG, finding that the ionized and molecular gas components are co-spatial and co-moving. The diffuse gas confined into the galaxy's tail is likely falling inward, providing additional fuel for star formation and AGN feedback, which is in accordance with models of chaotic cold accretion. The main source of ionization in the galaxy appears to be a mix between star formation and other energetic processes.

The star formation rate for M1931 BCG was calculated to be about 97 solar masses per year, with highest values in the galaxy's core. About 80% of the cluster's stellar mass is estimated to have formed more than 6 billion years ago. The intracluster medium (ICM) metallicity of M1931 was found to be consistent with the gas-phase metallicity measured in the BCG's interstellar medium (ISM). This finding suggests that the warm gas observed in the ISM of the galaxy has condensed from the ICM.

"The galaxy is a dispersion-dominated system, typical for massive, elliptical galaxies. The gas and stellar kinematics are decoupled, with the gaseous velocity fields being more closely related to the bulk motions of the intracluster medium," the authors of the paper concluded.

## The most distant radio galaxy discovered

Stacked y, J, H and K band image from the UKIDSS Large Area Survey, with contours from the 1.4 GHz VLA map (Saxena et al., 2018) overplotted for TGSS1530. Credit: Saxena et al., 2018.

An international team of astronomers has detected a new high-redshift radio galaxy (HzRG). The newly identified HzRG, designated TGSS1530, was found at a redshift of 5.72, meaning that it is the most distant radio galaxy known to date. The finding is reported in a paper published June 4 on arXiv.org.

High-redshift radio galaxies, which are among the most massive galaxies at their redshift, are known to contain large amounts of dust and gas. HzRGs are often located at the center of clusters and proto-clusters of galaxies. They could provide insights into the assembly and evolution of large scale structures in the universe.

Astronomers are particularly interested in finding new HzRGs at redshifts higher than 6.0, which are therefore from the so-called epoch of reionization – an early stage of the evolution of the universe, during which the cosmic gas went from neutral to ionized. Such radio galaxies could be used as unique tools to study the process of reionization in detail.

Recently, a group of researchers led by Aayush Saxena of the Leiden Observatory in the Netherlands, has found a new HzRG in the TIFR GMRT Sky Survey (TGSS) Alternative Data Release 1 (ADR1). In order to confirm the discovery, they conducted follow-up observations of this galaxy in April 2017 using the Gemini Multi-Object Spectrographs (GMOS) on the Gemini North telescope in Hawaii. Afterward, in February and May 2018, they carried out observations by employing the LBT Utility Camera in the Infrared (LUCI) on the Large Binocular Telescope (LBT) in Arizona.

What they found is a new radio galaxy at a redshift of 5.72, hence close to the end of the epoch of reionization.

"In this paper, we report the discovery a radio galaxy at a redshift of z = 5.72, TGSS1530, which was pre-selected as part of our sample of high-redshift radio galaxy candidates," the researchers wrote in the paper.

According to the study, TGSS1530 has an estimated size of approximately 11,400 light years – a value typical for radio galaxies at high redshifts. When it comes to its radio properties, they are comparable to other known radio galaxies at redshifts over 4.0. The researchers suggest that the high redshift of TGSS1530 together with relatively small radio and Lyman-alpha sizes may indicate that it may be a radio galaxy in an early phase of its evolution. Additionally, the astronomers found that the radio luminosity of TGSS1530 calculated at 150 MHz is 29.1 W/Hz, which places it at the most luminous end of the radio luminosity function at this epoch.

In concluding remarks, the authors of the paper noted that although TGSS1530 is a radio galaxy with the highest observed redshift, this could soon change with more sensitive, large-area surveys currently underway, such as the LOFAR Two-metre Sky Survey (LoTSS). Such surveys could be capable of detecting the first radio galaxy at a redshift higher than 6.0.

"Discovery of even a single bright radio galaxy at z > 6 would open up new ways to study the epoch of reionization in unparalleled detail, through searches for the 21cm absorption features left behind by the neutral hydrogen that pervaded the Universe at high redshifts," the astronomers concluded.

Abstract

## Discovery [ edit | edit source ]

Research published in the 24 October 2013 issue of the journal Nature by a team of astronomers from the University of Texas at Austin led by Steven Finkelstein, in collaboration with astronomers at the Texas A&M University, the National Optical Astronomy Observatory and University of California, Riverside, describes the discovery of the most distant galaxy known using deep optical and infrared images taken by the Hubble Space Telescope. Their discovery was confirmed by the W. M. Keck Observatory in Hawaii. MOSFIRE, a new instrument at the Keck Observatory that is extremely sensitive to infrared light, proved instrumental to this finding.

To measure galaxies at such large distances with definitive evidence, astronomers use spectroscopy and the phenomenon of redshift. Redshift occurs whenever a light source moves away from an observer. Astronomical redshift is seen due to the expansion of the universe, and sufficiently distant light sources (generally more than a few million light-years away) show redshift corresponding to the rate of increase in their distance from Earth. The redshift observed in astronomy can be measured because the emission and absorption spectra for atoms are distinctive and well known, calibrated from spectroscopic experiments in laboratories on Earth.

## A Stellar M-SFR-Z Relation MOSt DEFinitely Exists at z

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Title: The MOSDEF survey: a stellar mass-SFR-metallicity relation exists at z∼2.3
Authors: Ryan L. Sanders et al.
First Author’s Institution: University of California, Davis
Status: Published in ApJ

Galaxy evolution is a complicated thing! Our current theory is that gas comes in, stars get made & explode, the surrounding interstellar medium (ISM) heats up and gets enriched with metals, and then gas goes out. These processes are happening in different stages all across the galaxy and can make simulating and observing galaxy evolution very difficult. Thankfully, through years of observation of local galaxies, we know that some galactic properties are correlated! For example, Tremonti et al. (2004) showed that there is a relation between stellar mass (M) and gas-phase oxygen abundance (12 + log(O/H) or Z) in the local universe (redshift z

0). In 2008, Ellison et al. discovered that this M–Z relation also has a dependence on the star-formation rate (SFR), in the local universe. This local M–SFR–Z relation was shown later to be more correlated than the M–Z relation on its own!

The questions that then arise are: is there also evidence for a M–SFR–Z relation at high redshift? And if so, does it agree with the one at z

0? Or does it evolve with redshift? Many studies have tried to answer these questions, but most were based on large samples with low signal-to-noise (S/N) or small samples with intermediate S/N and have relied on a single metallicity indicator. But a 2018 study using a new, deep survey has changed that.

#### What Did They Do?

Completed in May 2016, the MOSFIRE Deep Evolution Field (MOSDEF) survey was a 4-year program in which the MOSFIRE instrument on the 10-m Keck 1 telescope was used to get near-IR spectra of

1,500 galaxies spanning redshifts 1.4 < z < 3.8. The authors of today’s article elected to use the

700 galaxies observed in the 2.01–2.61 redshift range. After S/N cuts, the authors were left with a 260-galaxy sample with an average redshift of z

2.3 (see Figure 1, left). To make a conclusion about the (possible) redshift evolution of the M–SFR–Z relation, the authors used a comparison sample of 208,529 star-forming galaxies at z

Figure 1: Left: The redshift distribution of their sample. The median redshift is z = 2.29. Middle: The SFR–M relation of the sample. Right: The sSFR–M relation of the sample. Here sSFR is the “specific star-formation rate,” which is just SFR/M. In the right two sections, the red-dashed line shows the best fit to the z

2.3 data. This best-fit relation will be used when calculating the M–SFR–Z relation. [Sanders et al. 2018]

#### What Did They Find?

The authors did detect a M–SFR–Z relation at z

2.3! This is best shown in Figure 2. This relation was found using the metallicity estimates from O3N2, N2, and N2O2. The ratios for R32 and O3 are double-valued with metallicity (think of these like a parabola) and can’t be used empirically to discover a relation like this. They can, however, be used to support a finding in this case, the results from R32 and O3 are consistent with those found from the other three. Results from O32 were inconsistent with their findings and the authors concluded that this was likely due to biases in the reddening correction. Another main goal of this project was to determine if the M–SFR–Z relation evolved with redshift — and the authors found that it did! At a given mass and SFR, the metallicity of the z

2.3 sample is 0.1 dex less than the z

0 sample, also shown in Figure 2. The authors speculate that this evolution may be caused by an increase in the mass-loading factor from z

2 and by a decrease in the metallicity of infalling gas at z

Figure 2: Shown above are the Z–M relations using O3N2, N2, and N2O2. Points are colored by star formation. Squares represent the z

0 data set while stars represent the z

2.3 set. The red-dashed line shows the best fit to the z

2.3 data. We see a M–SFR–Z relation at z

2.3 and at fixed mass and SFR, the z

2.3 set has 0.1 dex smaller metallicity than the z

#### What’s Left to Discover?

The authors established that a M–SFR–Z relation exists at z

2.3 and that this relation evolves with redshift. The existence of this relation implies that our understanding of galaxy evolution is right… at least up to z

2.3. The next step is to investigate this relation at higher redshifts, but that is no trivial task. As shown through the use of five emission-line ratios, measuring metallicities at high redshift can be difficult and will take great care. Uncertainties and inconsistencies with reddening corrections and other calibrations can cause large uncertainties in the results, like the case with O32. Thankfully, the introduction of large telescopes (like JWSTand TMT) will allow us to lessen these uncertainties through their increased sensitivities.

#### About the author, Huei Sears:

Huei Sears (she/her/hers) is a second-year graduate student at Ohio University studying astrophysics! Her research is focused on Gamma-Ray Burst host galaxies & how they fit into the mass-metallicity relationship. Previously she was at Michigan State University searching for the elusive period of B[e]supergiant, S18. In addition to research, she cares a lot about science communication, and is always looking for ways to make science more accessible. In her free time, she enjoys going to the gym, baking a new recipe, listening to Taylor Swift, watching the X-Files, and spending time with her little sister.

## Spatially Resolved Spectroscopic Properties of Low-Redshift Star-Forming Galaxies

I review the spatially resolved spectroscopic properties of low-redshift star-forming galaxies (and their retired counterparts) using results from the most recent optical integral field spectroscopy galaxy surveys. First, I briefly summarize the global spectroscopic properties of these galaxies, discussing the main ionization processes and the global relations described by the star-formation rates, gas-phase oxygen abundances, and average properties of their stellar populations (age and metallicity) in comparison with the stellar mass. Second, I present the local distribution of the ionizing processes down to kiloparsec scales, and I show how the global scaling relations found using integrated parameters (like the star-formation main sequence, mass–metallicity relation, and Schmidt–Kennicutt law) have local/resolved counterparts, with the global ones being, for the most part, just integrated/average versions of the local ones. I discuss the local/resolved star-formation histories (SFHs) and chemical-enrichment histories and their implications on the inside-out growth of galaxies. Third, I present the radial distributions of the surface densities of the properties explored globally and how they depend on the integrated galaxy properties.

Many global scaling relations present resolved counterparts (verified down to kiloparsec scales) that can explain them as well as the observed radial gradients in galaxies.

These relations are consequences of the local SFHs, the narrow range of the depletion times, and a local metal enrichment.

Deviations from these relations are due to dynamical and mixing processes, local exchange of gas (inflows, outflows, and fountains), depletion time differences, and/or differences in the resolved SFHs.

Ionization happens at local scales that may be driven by different physical processes, and it cannot be clearly understood using purely integrated quantities. The dominant ionization in galaxies has a stellar origin.

## Title: The Clustering of DESI-like Luminous Red Galaxies Using Photometric Redshifts

In this paper, we present measurements of the redshift-dependent clustering of a DESI-like luminous red galaxy (LRG) sample selected from the Legacy Survey imaging dataset, and use the halo occupation distribution (HOD) framework to fit the clustering signal. The photometric LRG sample in this study contains 2.7 million objects over the redshift range of 0.4 < z < 0.9 over 5655 sq. degrees. We have developed new photometric redshift (photo-z) estimates using the Legacy Survey DECam and WISE photometry, with σNMAD = 0.02 precision for LRGs. We compute the projected correlation function using new methods that maximize signal-to-noise while incorporating redshift uncertainties. We present a novel algorithm for dividing irregular survey geometries into equal-area patches for jackknife resampling. For a 5-parameter HOD model fit using the MultiDark halo catalog, we find that there is little evolution in HOD parameters except at the highest-redshifts. The inferred large-scale structure bias is largely consistent with constant clustering amplitude over time. In an appendix, we explore limitations of MCMC fitting using stochastic likelihood estimates resulting from applying HOD methods to N-body catalogs, and present a new technique for finding best-fit parameters in this situation. Accompanying this paper we have released the PRLS (Photometric Redshiftsmore » for the Legacy Surveys) catalog of photo-z’s obtained by applying the methods used in this work to the full Legacy Survey Data Release 8 dataset. This catalog provides accurate photometric redshifts for objects with z < 21 over more than 16,000 square degrees of sky. « less