Rebirth of Novae as Distance Indicators Due to Efficient, Large Telescopes

Our collaboration involves groups in Denmark, the U.S.A. Spain and of course New Zealand. Combining ground-based and satellite (IUEandHST) observations we aim to determine accurate and precise stellar fundamental parameters for the components of Magellanic Cloud Eclipsing Binaries as well as the distances to these systems and hence the parent galaxies themselves. This poster presents our latest progress.

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The First Galaxies in the Universe

10.23943/princeton/9780691144917.001.0001 ◽

2013 ◽

Author(s):

Abraham Loeb ◽

Steven R. Furlanetto

Keyword(s):

Galaxy Evolution ◽

Big Bang ◽

First Stars ◽

Distant Galaxies ◽

Formation And Evolution ◽

Early Galaxies ◽

First Galaxies ◽

Large Telescopes ◽

New Generation ◽

The Big Bang

This book provides a comprehensive, self-contained introduction to one of the most exciting frontiers in astrophysics today: the quest to understand how the oldest and most distant galaxies in our universe first formed. Until now, most research on this question has been theoretical, but the next few years will bring about a new generation of large telescopes that promise to supply a flood of data about the infant universe during its first billion years after the big bang. This book bridges the gap between theory and observation. It is an invaluable reference for students and researchers on early galaxies. The book starts from basic physical principles before moving on to more advanced material. Topics include the gravitational growth of structure, the intergalactic medium, the formation and evolution of the first stars and black holes, feedback and galaxy evolution, reionization, 21-cm cosmology, and more.

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Hunting for intermediate-mass black holes in globular clusters: an astrometric study of NGC 6441

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab474 ◽

2021 ◽

Vol 503 (1) ◽

pp. 1490-1506

Author(s):

Maximilian Häberle ◽

Mattia Libralato ◽

Andrea Bellini ◽

Laura L Watkins ◽

Jörg-Uwe Pott ◽

...

Keyword(s):

Globular Clusters ◽

Velocity Dispersion ◽

Angular Resolution ◽

Hubble Space Telescope ◽

High Mass ◽

High Angular Resolution ◽

Stellar Kinematics ◽

Intermediate Mass ◽

The Core ◽

Large Telescopes

ABSTRACT We present an astrometric study of the proper motions (PMs) in the core of the globular cluster NGC 6441. The core of this cluster has a high density and observations with current instrumentation are very challenging. We combine ground-based, high-angular-resolution NACO@VLT images with Hubble Space Telescope ACS/HRC data and measure PMs with a temporal baseline of 15 yr for about 1400 stars in the centremost 15 arcsec of the cluster. We reach a PM precision of ∼30 µas yr−1 for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other studies and extend already existing analyses of the stellar kinematics of NGC 6441 to its centremost region never probed before. In the innermost arcsecond of the cluster, we measure a velocity dispersion of (19.1 ± 2.0) km s−1 for evolved stars. Because of its high mass, NGC 6441 is a promising candidate for harbouring an intermediate-mass black hole (IMBH). We combine our measurements with additional data from the literature and compute dynamical models of the cluster. We find an upper limit of $M_{\rm IMBH} \lt 1.32 \times 10^4\, \textrm{M}_\odot$ but we can neither confirm nor rule out its presence. We also refine the dynamical distance of the cluster to $12.74^{+0.16}_{-0.15}$ kpc. Although the hunt for an IMBH in NGC 6441 is not yet concluded, our results show how future observations with extremely large telescopes will benefit from the long temporal baseline offered by existing high-angular-resolution data.

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The effects of peculiar velocities in SN Ia environments on the local H0 measurement

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3456 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3728-3742

Author(s):

Thomas M Sedgwick ◽

Chris A Collins ◽

Ivan K Baldry ◽

Philip A James

Keyword(s):

Hubble Constant ◽

Density Parameter ◽

Host Galaxies ◽

Peculiar Velocities ◽

Standard Candle ◽

Modern Cosmology ◽

Type Ia ◽

The Difference ◽

Ia Supernovae ◽

Distance Indicators

ABSTRACT The discrepancy between estimates of the Hubble constant (H0) measured from local (z ≲ 0.1) scales and from scales of the sound horizon is a crucial problem in modern cosmology. Peculiar velocities (vpec) of standard candle distance indicators can systematically affect local H0 measurements. We here use 2MRS galaxies to measure the local galaxy density field, finding a notable z < 0.05 underdensity in the SGC-6dFGS region of 27 ± 2 per cent. However, no strong evidence for a ‘Local Void’ pertaining to the full 2MRS sky coverage is found. Galaxy densities are used to measure a density parameter, Δϕ+−, which we introduce as a proxy for vpec that quantifies density gradients along a supernova (SN) line of sight. Δϕ+− is found to correlate with local H0 estimates from 88 Pantheon Type Ia supernovae (SNe Ia; 0.02 < z < 0.05). Density structures on scales of ∼50 Mpc are found to correlate strongest with H0 estimates in both the observational data and in mock data from the MDPL2-Galacticus simulation. Using trends of H0 with Δϕ+−, we can correct for the effects of density structure on local H0 estimates, even in the presence of biased vpec. However, the difference in the inferred H0 estimate with and without the peculiar velocity correction is limited to < 0.1 per cent. We conclude that accounting for environmentally induced peculiar velocities of SN Ia host galaxies does not resolve the tension between local and CMB-derived H0 estimates.

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An updated Type II supernova Hubble diagram

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731271 ◽

2018 ◽

Vol 611 ◽

pp. A25 ◽

Cited By ~ 9

Author(s):

E. E. E. Gall ◽

R. Kotak ◽

B. Leibundgut ◽

S. Taubenberger ◽

W. Hillebrandt ◽

...

Keyword(s):

Spectral Lines ◽

Balmer Line ◽

Type Ii ◽

Dependent Relation ◽

Measuring Techniques ◽

Distance Indicators ◽

Larger Sample ◽

Current Record ◽

Initial Results ◽

The Continuum

We present photometry and spectroscopy of nine Type II-P/L supernovae (SNe) with redshifts in the 0.045 ≲ z ≲ 0.335 range, with a view to re-examining their utility as distance indicators. Specifically, we apply the expanding photosphere method (EPM) and the standardized candle method (SCM) to each target, and find that both methods yield distances that are in reasonable agreement with each other. The current record-holder for the highest-redshift spectroscopically confirmed supernova (SN) II-P is PS1-13bni (z = 0.335−0.012+0.009), and illustrates the promise of Type II SNe as cosmological tools. We updated existing EPM and SCM Hubble diagrams by adding our sample to those previously published. Within the context of Type II SN distance measuring techniques, we investigated two related questions. First, we explored the possibility of utilising spectral lines other than the traditionally used Fe iiλ5169 to infer the photospheric velocity of SN ejecta. Using local well-observed objects, we derive an epoch-dependent relation between the strong Balmer line and Fe iiλ5169 velocities that is applicable 30 to 40 days post-explosion. Motivated in part by the continuum of key observables such as rise time and decline rates exhibited from II-P to II-L SNe, we assessed the possibility of using Hubble-flow Type II-L SNe as distance indicators. These yield similar distances as the Type II-P SNe. Although these initial results are encouraging, a significantly larger sample of SNe II-L would be required to draw definitive conclusions.

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