The redshift and star formation mode of AzTEC2: a pair of massive galaxies at $z=4.63$
E. F. Jiménez-Andrade, J. A. Zavala, B. Magnelli, C. M. Casey, D. Liu, E. Romano-Díaz, E. Schinnerer, K. Harrington, I. Aretxaga, A. Karim, J. Staguhn, A. D. Bu… 展开作者
E. F. Jiménez-Andrade, J. A. Zavala, B. Magnelli, C. M. Casey, D. Liu, E. Romano-Díaz, E. Schinnerer, K. Harrington, I. Aretxaga, A. Karim, J. Staguhn, A. D. Burnham, A. Montaña, V. Smolčić, M. Yun, F. Bertoldi, D. Hughes
备注：
19 pages, 6 figures, accepted for publication in ApJ
We combine observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the NOrthern Extended Millimeter Array (NOEMA) to assess the redshift and to study the star formation conditions in AzTEC2: one of the brightest sub-millimeter galaxies (SMGs) in the COSMOS field ($S_{\rm 1.1mm}=10.5\pm1.4$mJy). Our high-resolution observations confirm that AzTEC2 splits into two components (namely AzTEC2-A and AzTEC2-B) for which we detect [C$\,$II] and $^{12}$CO(5$\to$4) line emission, implying a redshift of $4.626\pm0.001$ ($4.633\pm0.001$) for AzTEC2-A (AzTEC2-B) and ruling out previous associations with a galaxy at $z\sim1$. We use the $^{12}$CO(5$\to$4) line emission and adopt typical SMG-like gas excitation conditions to estimate the molecular gas mass, which is $M_{\rm gas}(α_{\rm CO}/2.5)=2.1\pm0.4 \times10^{11}{\rm M}_\odot$ for AzTEC2-A, and a factor four lower for AzTEC2-B. With the infrared-derived star formation rate of AzTEC2-A ($1920\pm100 \,M_\odot{\rm \, yr}^{-1}$) and AzTEC2-B ($710\pm 35\,M_\odot{\rm \,yr}^{-1}$), they both will consume their current gas reservoir within $(30-200)\,$Myr. We find evidence of a rotation-dominated [C$\,$II] disk in AzTEC2-A, with a de-projected rotational velocity of $v_{\rm rot}(i=39^\circ)=660\pm130{\rm \,km\,s}^{-1}$, velocity dispersion $\lesssim100{\rm \,km\,s}^{-1}$, and dynamical mass of $M_{\rm dyn}(i=39^\circ)=2.6^{+1.2}_{-0.9}\times10^{11}\,M_\odot$. We propose that an elevated gas accretion rate from the cosmic web might be the main driver of the intense levels of star formation in AzTEC2-A, which might be further enhanced by gravitational torques induced by its minor companion (AzTEC2-B). These results strengthen the picture whereby the population of single-dish selected SMGs is rather heterogeneous, including a population of pairs of massive, highly-active galaxies in a pre-coalescence phase.
We present a sample of local analogs for high-redshift galaxies selected in the Sloan Digital Sky Survey (SDSS). The physical conditions of the interstellar medium (ISM) in these local analogs resemble those in high-redshift galaxies. These galaxies are selected based on their positions in the [OIII]/H$β$ versus [NII]/H$α$ nebular emission-line diagnostic diagram. We show that these local analogs share similar physical properties with high-redshift galaxies, including high specific star formation rates (sSFRs), flat UV continuums and compact galaxy sizes. In particular, the ionization paramete…
Submillimetre (submm) observations of WISE-selected, dusty, luminous, high-redshift galaxies have revealed intriguing overdensities around them on arcmin scales. They could be the best signposts of overdense environments on the sky.
We study the direct gas-phase oxygen abundance using the well-detected auroral [OIII]4363 line in the stacked spectra of a sample of local analogs of high-redshift galaxies. These local analogs share the same location as $z\sim2$ star-forming galaxies on the Baldwin-Phillips-Terlevich diagram. This type of analog has the same ionized interstellar medium (ISM) properties as high-redshift galaxies. We establish empirical metallicity calibrations between the direct gas-phase oxygen abundances ($7.8<12+\log(\rm{O/H})<8.4$) and the N2/O3N2 indices in our local analogs. We find significant systemati…
Massive quiescent galaxies at high redshift can shed light on the processes of galaxy mass assembly and quenching of the star formation at early epochs. We present observer-frame color-color diagrams designed to identify candidate quiescent galaxies from z=2.5 up to the highest redshifts, that can be then be selected for spectroscopic follow-up observations. The application to the COSMOS2015 catalog shows that, after refining the selection with SED fitting, the number of massive old quiescent galaxies exceeds the forecast of state-of-the-art semi-analytic models, pointing out the need of an im…
We compare the relations among various integrated characteristics of ~25,000 low-redshift (z<1.0) compact star-forming galaxies (CSFGs) from Data Release 16 (DR16) of the Sloan Digital Sky Survey (SDSS) and of high-redshift (z>1.5) star-forming galaxies (SFGs) with respect to oxygen abundances, stellar masses M*, far-UV absolute magnitudes M(FUV), star-formation rates SFR and specific star-formation rates sSFR, Lyman-continuum photon production efficiencies (xi_ion), UV continuum slopes β, [OIII]5007/[OII]3727 and [NeIII]3868/[OII]3727 ratios, and emission-line equivalent widths EW([OII]3727),…
We study the physical mechanisms that cause the offset between low-redshift and high-redshift galaxies on the [OIII]/H$β$ versus [NII]/H$α$ ``Baldwin, Phillips & Terlevich'' (BPT) diagram using a sample of local analogues of high-redshift galaxies. These high-redshift analogue galaxies are selected from the Sloan Digital Sky Survey. Located in the same region on the BPT diagram as the ultra-violet selected galaxies at $z\sim2$, these high-redshift analogue galaxies provide an ideal local benchmark to study the offset between the local and high-redshift galaxies on the BPT diagram. We compare t…
We examine the redshift evolution of standard strong emission-line diagnostics for Hbeta-selected star-forming galaxies using the local SDSS sample and a new z = 0.2 - 2.3 sample obtained from HST WFC3 grism and Keck DEIMOS and MOSFIRE data. We use the SDSS galaxies to show that there is a systematic dependence of the strong emission-line properties on Balmer-line luminosity, which we interpret as showing that both the N/O abundance and the ionization parameter increase with increasing line luminosity. Allowing for the luminosity dependence tightens the diagnostic diagrams and the metallicity …
One of the primary goals for the upcoming James Webb Space Telescope (JWST) is to observe the first galaxies. Predictions for planned and proposed surveys have typically focused on average galaxy counts, assuming a random distribution of galaxies across the observed field. The first and most massive galaxies, however, are expected to be tightly clustered, an effect known as cosmic variance. We show that cosmic variance is likely to be the dominant contribution to uncertainty for high-redshift mass and luminosity functions, and that median high-redshift and high-mass galaxy counts for planned o…
Using simulations we demonstrate that some of the published redshift distributions of submillimetre galaxies (SMGs) at different wavelengths, which were previously reported to be statistically different, are consistent with a parent distribution of the same population of galaxies. The redshift distributions which peak at z_med=2.9, 2.6, 2.2, 2.2, and 2.0 for galaxies selected at 2 and 1.1 mm, and 870, 850, and 450 um respectively, can be derived from a single parent redshift distribution, in contrast with previous studies. The differences can be explained through wavelength selection, depth of…
We present a sample of 22 blue ($(B-V)_{AB}<0.45$), luminous ($M_{B,AB}<-18.9$), metal-poor galaxies in the $0.69<z<0.88$ redshift range, selected from the DEEP2 galaxy redshift survey. Their spectra contain the $[OIII]\lambda4363$ auroral line, the $[OII]λ\lambda3726,3729$ doublet and the strong nebular $[OIII]λλ4959,5007$ emission lines. The ionised gas-phase oxygen abundances of these galaxies lie between $7.62<12+\log O/H < 8.19$, i.e. between $1/10 Z_{\odot}$ and $1/3 Z_{\odot}$. We find that galaxies in our sample have comparable metallicities to other intermediate-redshift samples, but …
I provide an overview about star-forming galaxies at high redshift and their physical properties. Starting from the populations of Ly-$α$ emitters and Lyman break galaxies, I summarize their common features and distinction. Then I summarize recent insight onto their physical properties gained from SED models including nebular emission, and various implications from these studies on the properties of star-formation at high redshift. Finally, I present new results and an overview on the dust content and UV attenuation of $z>6$ galaxies obtained from IRAM and ALMA observations.
High-redshift radio galaxies (HzRGs) are some of the rarest objects in the Universe. They are often found to be the most massive galaxies observed at any epoch and are known to harbour active supermassive black holes that give rise to powerful relativistic jets. Finding such galaxies at high redshifts can shed light on the processes that shaped the most massive galaxies very early in the Universe. We have started a new campaign to identify and follow-up promising radio sources selected at 150 MHz in a bid to identify the most distant radio galaxies and study their properties, both intrinsic an…
We created a catalog of photometric redshift of ~3,000,000 SDSS galaxies annotated by their broad morphology. The photometric redshift was optimized by testing and comparing several pattern recognition algorithms and variable selection strategies, trained and tested on a subset of the galaxies in the catalog that had spectra. The galaxies in the catalog have i magnitude brighter than 18 and Petrosian radius greater than 5.5''. The majority of these objects are not included in previous SDSS photometric redshift catalogs such as the photoz table of SDSS DR12. Analysis of the catalog shows that t…
We investigate the median flattening of galaxies at $0.2<z<4.0$ in all five CANDELS/3D-HST fields via the apparent axis ratio $q$. We separate the sample into bins of redshift, stellar-mass, sérsic index, size, and UVJ determined star-forming state to discover the most important drivers of the median $q$ ($q_{med}$). Quiescent galaxies at $z<1$ and $M_{*}>10^{11}M_{\odot}$ are rounder than those at lower masses, consistent with the hypothesis that they have grown significantly through dry merging. The massive quiescent galaxies at higher redshift become flatter, and are as flat as star forming…
Correlations between black holes and their host galaxies provide insight into what drives black hole-host co-evolution. We use the Meraxes semi-analytic model to investigate the growth of black holes and their host galaxies from high redshift to the present day. Our modelling finds no significant evolution in the black hole-bulge and black hole-total stellar mass relations out to a redshift of 8. The black hole-total stellar mass relation has similar but slightly larger scatter than the black hole-bulge relation, with the scatter in both decreasing with increasing redshift. In our modelling th…
The thermal history of the Universe is introduced within the Debye Gravitational Theory (DGT), a thermodynamic theory of induced gravity, and allows to obtain the evolution of systems with the redshift. DGT reproduce the ESO VLT observations, showing falling outer rotation curves for galaxies at redshift above 0.77. A scaling law is observed in the radial acceleration relation (RAR) of galaxies. For accelerations smaller than $\sim 10^{-10}ms^{-1}$ the observed acceleration $g_{obs}$ decreases more slowly than acceleration generated by the baryonic mass $g_{bar}$, following always the relation…
New challenges in the modelling of galaxy spectra are bound to emerge as upcoming telescopes like the James Webb Space Telescope will allow us to detect galaxies at fainter flux levels and higher redshifts than ever before. Here, we highlight three modelling problems that may become relevant for upcoming observations in the rest-frame ultraviolet/optical at the high-redshift frontier: stellar initial mass function sampling effects, Population III signatures and the leakage of ionizing radiation into the intergalactic medium.
We study the relation between the UV-slope, $β$, and the ratio between the infrared- and UV-luminosities (IRX) of galaxies from TNG50, the latest installment of the IllustrisTNG galaxy formation simulations. We select 7280 star-forming main-sequence (SFMS) galaxies with stellar mass $10^9M_\odot$ at redshifts $0 \leq z \leq 4$ and perform radiative transfer with SKIRT to model effects of interstellar medium dust on the emitted stellar light. Assuming a Milky Way (MW) dust type and a dust-to-metal ratio of 0.3, we find that TNG50 SFMS galaxies generally agree with observationally-derived IRX-$β…
We investigate the redshift evolution of the [OIII]/Hb nebular emission line ratio for a sample of galaxies spanning the redshift range 0 < z < 4. We compare the observed evolution to a set of theoretical models which account for the independent evolution of chemical abundance, ionization parameter and interstellar-medium (ISM) pressure in star-forming galaxies with redshift. Accounting for selection effects in the combined datasets, we show that the evolution to higher [OIII]/Hb ratios with redshift is a real physical effect which is best accounted for by a model in which the ionization param…
The thermal history of the Universe is included in the Debye Gravitational Theory (DGT) to describe the speed of rotation of the galaxies. The DGT incorporate the temperature of Debye in the entropic gravitational theory. According to the DGT, the expression of the rotation of the galaxies is not a continuous function of the redshift, there is a discontinuity at $\sim 0.77$. According to their redshift, the galaxies form two groups. (a) Those with redshift above 0.77 with declining rotation curves like $R^β$ with $β\leq -0.5$ (Newtonian regime). (b) Those with redshift below 0.77 with rising r…
Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so called dropout technique or Ly-alpha selection. However, the availability of multifilter data allows now replacing the dropout selections by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims. Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other…
We investigate the relation between stellar mass ($M_\star$), star formation rate (SFR), and metallicity ($Z$) of galaxies, so called the fundamental metallicity relation, in the galaxy sample of the Sloan Digital Sky Survey Data Release 7. We separate the galaxies into narrow redshift bins and compare the relation at different redshifts, and find statistically significant ($> 99$%) evolution. We test various observational effects that might cause seeming $Z$ evolution, and find it difficult to explain the evolution of the relation only by the observational effects. In the current sample of lo…
The number of galaxies at a given flux as a function of the redshift, $z$, is derived when the $z$-distance relation is non-standard. In order to compare different models, the same formalism is also applied to the standard cosmology. The observed luminosity function for galaxies of the zCOSMOS catalog at different redshifts is modelled by a new luminosity function for galaxies, which is derived by the truncated beta probability density function. Three astronomical tests, which are the photometric maximum as a function of the redshift for a fixed flux, the mean value of the redshift for a fixed…
An analysis of 913 groups of galaxies and 56 Abell clusters from the literature has been made in order to estimate the mean of the fraction of strong barred galaxies SB/(S+SB) in the redshift interval 0 < z < 0.066
The dwarf galaxies of the Local Group are believed to be similar to the most abundant galaxies during the epoch of reionization (z>6). As a result of their proximity, there is a wealth of information that can be obtained about these galaxies; however, due to their low surface brightnesses, detecting their progenitors at high redshifts is challenging. We compare the physical properties of these dwarf galaxies to those of galaxies detected at high redshifts using Hubble Space Telescope and Spitzer observations and consider the promise of the upcoming James Webb Space Telescope on the prospects f…
Performance of Photometric Template Fitting for Ultra-High Redshift Galaxies
Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Department of Physics and Astronomy, University of Missouri（密苏里大学物理与天文学系）；DARK Cosmology Center, University of Copenhagen（哥本哈根大学暗宇宙学中心）；California Institute of Technology（加州理工学院）
Correlations between jet power and active time for z < 0.1 high excitation and low excitation radio galaxies are explored as well as evidence in favor of a specific, non-random distribution for these objects including mid-infrared emitting radio galaxies as a function of environment and redshift. In addition, so-called weak line radio galaxies with FRII jet morphology have been identified as a class of active galaxies in the process of shutting down. This paper identifies common features between these seemingly disparate phenomena described above for the population of radio galaxies, and strin…
A galaxy's metallicity provides a record of star formation, gas accretion, and gas outflow, and is therefore one of the most informative measurements that can be made at high redshift. It is also one of the most difficult. I review methods of determining chemical abundances in distant star-forming galaxies, and summarize results for galaxies at 1<z<3. I then focus on the mass-metallicity relation, its evolution with redshift, and its uses in constraining inflows and outflows of gas, and conclude with a brief discussion of future prospects for metallicity measurements at high redshift.
We report the identification of elongated (triaxial or prolate) galaxies in cosmological simulations at $z\simeq2$. These are preferentially low-mass galaxies ($M_s \le 10^{9.5} \ M_\odot$), residing in dark-matter (DM) haloes with strongly elongated inner parts, a common feature of high-redshift DM haloes in the $Λ$CDM cosmology. Feedback slows formation of stars at the centres of these halos, so that a dominant and prolate DM distribution gives rise to galaxies elongated along the DM major axis. As galaxies grow in stellar mass, stars dominate the total mass within the galaxy half-mass radiu…
Precision-era optical cluster cosmology calls for a precise definition of the red sequence (RS), consistent across redshift. To this end, we present the Red Dragon algorithm: an error-corrected multivariate Gaussian mixture model (GMM). Simultaneous use of multiple colors and smooth evolution of GMM parameters result in a continuous RS and blue cloud (BC) characterization across redshift, avoiding the discontinuities of red fraction inherent in swapping RS selection colors. Based on a mid-redshift spectroscopic sample of SDSS galaxies, a RS defined by Red Dragon selects quenched galaxies (low …
We apply Bayesian statistics with prior probabilities of galaxy surface luminosity (SL) to improve photometric redshifts. We apply the method to a sample of 1266 galaxies with spectroscopic redshifts in the GOODS North and South fields at 0.1 < z < 2.0. We start with spectrophotometric redshifts (SPZs) based on Probing Evolution and Reionization Spectroscopically grism spectra, which cover a wavelength range of 6000-9000A, combined with (U)BViz(JHK) broadband photometry in the GOODS fields. The accuracy of SPZ redshifts is estimated to be σ(Δ(z))=0.035 with an systematic offset of -0.026, wher…
The redshift distribution of galactic-scale lensing systems provides a laboratory to probe the velocity dispersion function (VDF) of early-type galaxies (ETGs) and measure the evolution of early-type galaxies at redshift z ~ 1. Through the statistical analysis of the currently largest sample of early-type galaxy gravitational lenses, we conclude that the VDF inferred solely from strong lensing systems is well consistent with the measurements of SDSS DR5 data in the local universe. In particular, our results strongly indicate a decline in the number density of lenses by a factor of two and a 20…
We use the semi-analytical model of galaxy formation GALFORM to characterise an indirect signature of AGN feedback in the environment of radio galaxies at high redshifts. The predicted environment of radio galaxies is denser than that of radio-quiet galaxies with the same stellar mass. This is consistent with observational results from the CARLA survey. Our model shows that the differences in environment are due to radio galaxies being hosted by dark matter haloes that are ~1.5 dex more massive than those hosting radio-quiet galaxies with the same stellar mass. By running a control-simulation …
