scholarly journals The predicted properties of helium-enriched globular cluster progenitors at high redshift

2020 ◽  
Vol 496 (3) ◽  
pp. 3222-3234
Author(s):  
David M Nataf ◽  
Shunsaku Horiuchi ◽  
Guglielmo Costa ◽  
Rosemary F G Wyse ◽  
Yuan-Sen Ting ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Cluster Formation ◽  
Stellar Populations ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
Galactic Astronomy

ABSTRACT Globular cluster progenitors may have been detected by Hubble Space Telescope, and are predicted to be observable with James Webb Space Telescope (JWST) and ground-based extremely large telescopes with adaptive optics. This has the potential to elucidate the issue of globular cluster formation and the origins of significantly helium-enriched subpopulations, a problem in Galactic astronomy with no satisfactory theoretical solution. Given this context, we use model stellar tracks and isochrones to investigate the predicted observational properties of helium-enriched stellar populations in globular cluster progenitors. We find that, relative to helium-normal populations, helium-enriched (ΔY = +0.12) stellar populations similar to those inferred in the most massive globular clusters, are expected, modulo some rapid fluctuations in the first ∼30 Myr, to be brighter and redder in the rest frame. At fixed age, stellar mass, and metallicity, a helium-enriched population is predicted to converge to being ∼0.40 mag brighter at $\lambda \approx 2.0\, {\mu \rm m}$, and to be 0.30-mag redder in the JWST–NIRCam colour (F070W − F200W), and to actually be fainter for $\lambda \lesssim 0.50 \, {\mu \rm m}$. Separately, we find that the time-integrated shift in ionizing radiation is a negligible $\sim \!5{{\ \rm per\ cent}}$, though we show that the Lyman-α escape fraction could end up higher for helium-enriched stars.

9. The next telescopes

2016 ◽  
pp. 122-138
Author(s):  
Geoff Cottrell
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Adaptive Optics ◽  
Hubble Space Telescope ◽  
Scientific Instrument ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
First Galaxies ◽  
New Generation ◽  
Optical Telescopes

Each question that telescopes have helped answer has led to new questions: what is dark matter and dark energy? How did the first galaxies form? Are there habitable, Earth-like exoplanets? To address these questions, a new generation of telescopes are being built. ‘The next telescopes’ describes some of these, including the three extremely large infrared/optical telescopes, equipped with adaptive optics systems, due to start operating in the next decade. Other new telescopes discussed are the Square Kilometre Array, a radio telescope that will soon be the world’s largest scientific instrument, and the James Webb Space Telescope due to be launched in 2018, which is the 100 times more powerful successor to the Hubble Space Telescope.

scholarly journals Hubble Space Telescope Studies of the Dense Central Regions of Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 19-28
Author(s):  
Puragra Guhathakurta ◽  
Brian Yanny ◽  
Donald P. Schneider ◽  
John N. Bahcall
Keyword(s):  
Density Profile ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Core Collapse ◽  
Red Giants ◽  
Space Telescope ◽  
Blue Straggler ◽  
Central Regions ◽  
Stellar Density

We present results from an ongoing program to probe the dense central parts of Galactic globular clusters using multicolor Hubble Space Telescope images (WF/PC-I and WFPC2). Our sample includes the dense clusters M15, 47 Tuc, M30, NGC 6624, M3 and M13. The two main goals of our program are to measure the shape of stellar density profile in clusters (the slope of the density cusp in post core collapse clusters, in particular) and to understand the nature of evolved stellar populations in very dense regions and their variation as a function of radius. The latter includes studies of blue straggler stars and of the central depletion of bright red giants. Our recent WFPC2 study of M15 is described in detail.

Internal kinematics of multiple stellar populations in globular clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 324-328
Author(s):  
Mattia Libralato
Keyword(s):  
High Precision ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Stellar Systems ◽  
Proper Motions ◽  
Space Telescope ◽  
Formation And Evolution ◽  
Galactic Globular Clusters ◽  
Shed Light

AbstractSpectroscopy and photometry have revealed existence, complexity and properties of the multiple stellar populations (mPOPs) hosted in Galactic globular clusters. However, the conundrum of the formation and evolution of mPOPs is far from being completely exploited: the available pieces of information seem not enough to shed light on these topics. Astrometry, and in particular high-precision proper motions, can provide us the sought-after answers about how mPOPs formed and have evolved in these ancient stellar systems. In the following, I present a brief overview of the observational results on the internal kinematics of the mPOPs in some GCs thanks to Hubble Space Telescope high-precision proper motions.

scholarly journals Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud – IV. Evidence for multiple populations in Hodge 11 and NGC 2210

2019 ◽  
Vol 486 (4) ◽  
pp. 5581-5599 ◽  
Author(s):  
Christina K Gilligan ◽  
Brian Chaboyer ◽  
Jeffrey D Cummings ◽  
Dougal Mackey ◽  
Roger E Cohen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Cluster Formation ◽  
Stellar Populations ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Wide Field ◽  
Horizontal Branch ◽  
Advanced Camera For Surveys

Abstract We present a multiple population search in two old Large Magellanic Cloud (LMC) Globular clusters, Hodge 11 and NGC 2210. This work uses data from the Advanced Camera for Surveys and Wide Field Camera 3 on the Hubble Space Telescope from programme GO-14164 in Cycle 23. Both of these clusters exhibit a broadened main sequence with the second population representing (20 ± ∼5) per cent for NGC 2210 and (30 ± ∼5) per cent for Hodge 11. In both clusters, the smaller population is redder than the primary population, suggesting CNO variations. Hodge 11 also displays a bluer second population in the horizontal branch, which is evidence for helium enhancement. However, even though NGC 2210 shows similarities to Hodge 11 in the main sequence, there does not appear to be a second population on NGC 2210’s horizontal branch. This is the first photometric evidence that ancient LMC Globular clusters exhibit multiple stellar populations.

scholarly journals Studying the physical properties of tidal features – I. Extracting morphological substructure in CANDELS observations and VELA simulations

2019 ◽  
Vol 486 (2) ◽  
pp. 2643-2659 ◽  
Author(s):  
Kameswara Bharadwaj Mantha ◽  
Daniel H McIntosh ◽  
Cody P Ciaschi ◽  
Rubyet Evan ◽  
Henry C Ferguson ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Software Tool ◽  
Space Telescope ◽  
Visual Appearance ◽  
James Webb Space Telescope ◽  
Profile Fitting ◽  
Major Merger ◽  
Merger Rate

Abstract The role of major mergers in galaxy evolution remains a key open question. Existing empirical merger identification methods use non-parametric and subjective visual classifications that can pose systematic challenges to constraining merger histories. As a first step towards overcoming these challenges, we develop and share publicly a new python-based software tool that identifies and extracts the flux-wise and area-wise significant contiguous regions from the model-subtracted residual images produced by popular parametric light-profile fitting tools (e.g. galfit). Using Hubble Space Telescope (HST) H-band single-Sérsic residual images of 17 CANDELS galaxies, we demonstrate the tools ability to measure the surface brightness and improve the qualitative identification of a variety of common residual features (disc structures, spiral substructures, plausible tidal features, and strong gravitational arcs). We test our method on synthetic HST observations of a z ∼ 1.5 major merger from the VELA hydrodynamic simulations. We extract H-band residual features corresponding to the birth, growth, and fading of tidal features during different stages and viewing orientations at CANDELS depths and resolution. We find that the extracted features at shallow depths have noisy visual appearance and are susceptible to viewing angle effects. For a VELA z ∼ 3 major merger, we find that James Webb Space Telescope NIRCam observations can probe high-redshift tidal features with considerable advantage over existing HST capabilities. Further quantitative analysis of plausible tidal features extracted with our new software hold promise for the robust identification of hallmark merger signatures and corresponding improvements to merger rate constraints.

scholarly journals Low-luminosity Galaxies in the Early Universe Have Observed Sizes Similar to Star Cluster Complexes

2021 ◽  
Vol 162 (6) ◽  
pp. 255
Author(s):  
R. J. Bouwens ◽  
G. D. Illingworth ◽  
P. G. van Dokkum ◽  
B. Ribeiro ◽  
P. A. Oesch ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
High Redshift ◽  
Cluster Formation ◽  
Star Cluster ◽  
Single Star ◽  
Cluster Complexes ◽  
Star Forming ◽  
Comparison Sample ◽  
Upper Limits

Abstract We compare the sizes and luminosities of faint z = 6–8 galaxies magnified by the Hubble Frontier Fields clusters with star-forming regions, as well as more evolved objects, in the nearby universe. Our high-redshift comparison sample includes 330 z = 6–8 galaxies, for which size measurements were made as part of a companion study where lensing magnifications were estimated from various public models. Accurate size measurements for these sources are complicated by the lens model uncertainties, but other results and arguments suggest that faint galaxies are small, as discussed in a companion study. The measured sizes for sources in our comparison sample range from <50 pc to ∼500 pc. For many of the lowest-luminosity sources, extremely small sizes are inferred, reaching individual sizes as small as 10–30 pc, with several sources in the 10–15 pc range with our conservative magnification limits. The sizes and luminosities are similar to those of single star cluster complexes like 30 Doradus in the lower-redshift universe and—in a few cases—super star clusters. The identification of these compact, faint star-forming sources in the z ∼ 6–8 universe also allows us to set upper limits on the proto-globular cluster luminosity function at z ∼ 6. By comparisons of the counts and sizes with recent models, we rule out (with some caveats) proto-globular cluster formation scenarios favoring substantial (ξ = 10) post-formation mass loss and set useful upper limits on others. Our size results suggest we may be very close to discovering a bona fide population of forming globular clusters at high redshift.

scholarly journals The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters – XIX. A chemical tagging of the multiple stellar populations over the chromosome maps

2019 ◽  
Vol 487 (3) ◽  
pp. 3815-3844 ◽  
Author(s):  
A F Marino ◽  
A P Milone ◽  
A Renzini ◽  
F D’Antona ◽  
J Anderson ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Empirical Relation ◽  
Light Element ◽  
Stellar Populations ◽  
Type I ◽  
Type Ii ◽  
Chemical Abundances ◽  
Space Telescope ◽  
Galactic Globular Clusters

Abstract The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters (GCs) has investigated GCs and their stellar populations. In previous papers of this series we have introduced a pseudo two-colour diagram, or ‘chromosome map’ (ChM) that maximizes the separation between the multiple populations. We have identified two main classes of GCs: Type I, including ∼83 per cent of the objects, and Type II clusters. Both classes host two main groups of stars, referred to in this series as first (1G) and second generation (2G). Type II clusters host more complex ChMs, exhibiting two or more parallel sequences of 1G and 2G stars. We exploit spectroscopic elemental abundances from the literature to assign the chemical composition to the distinct populations as identified on the ChMs of 29 GCs. We find that stars in different regions of the ChM have different compositions: 1G stars share the same light-element content as field stars, while 2G stars are enhanced in N and Na and depleted in O. Stars with enhanced Al, as well as stars with depleted Mg, populate the extreme regions of the ChM. We investigate the intriguing colour spread among 1G stars observed in many Type I GCs, and find no evidence for internal variations in light elements among these stars, whereas either a ∼0.1 dex iron spread or a variation in He among 1G stars remains to be verified. In the attempt of analysing the global properties of the multiple-population phenomenon, we have constructed a universal ChM, which highlights that, though very variegate, the phenomenon has some common pattern among all the analysed GCs. The universal ChM reveals a tight connection with Na abundances, for which we have provided an empirical relation. The additional ChM sequences observed in Type II GCs are enhanced in metallicity and, in some cases, s-process elements. Omega Centauri can be classified as an extreme Type II GC, with a ChM displaying three main extended ‘streams’, each with its own variations in chemical abundances. One of the most noticeable differences is found between the lower and upper streams, with the latter, associated with higher He, being also shifted towards higher Fe and lower Li abundances. We publicly release the ChMs.

Sign in / Sign up

Export Citation Format

Share Document