scholarly journals Asymmetric surface brightness structure of caustic crossing arc in SDSS J1226+2152: a case for dark matter substructure

2020 ◽  
Vol 495 (3) ◽  
pp. 3192-3208
Author(s):  
Liang Dai ◽  
Alexander A Kaurov ◽  
Keren Sharon ◽  
Michael Florian ◽  
Jordi Miralda-Escudé ◽  
...  

ABSTRACT We study the highly magnified arc SGAS J122651.3+215220 caused by a star-forming galaxy at zs = 2.93 crossing the lensing caustic cast by the galaxy cluster SDSS J1226+2152 (zl = 0.43), using Hubble Space Telescope observations. We report in the arc several asymmetric surface brightness features whose angular separations are a fraction of an arcsecond from the lensing critical curve and appear to be highly but unequally magnified image pairs of underlying compact sources, with one brightest pair having clear asymmetry consistently across four filters. One explanation of unequal magnification is microlensing by intracluster stars, which induces independent flux variations in the images of individual or groups of source stars in the lensed galaxy. For a second possibility, intracluster dark matter subhaloes invisible to telescopes effectively perturb lensing magnifications near the critical curve and give rise to persistently unequal image pairs. Our modelling suggests, at least for the most prominent identified image pair, that the microlensing hypothesis is in tension with the absence of notable asymmetry variation over a six-year baseline, while subhaloes of ∼106–$10^8\, \mathrm{ M}_\odot$ anticipated from structure formation with cold dark matter typically produce stationary and sizable asymmetries. We judge that observations at additional times and more precise lens models are necessary to stringently constrain temporal variability and robustly distinguish between the two explanations. The arc under this study is a scheduled target of a Director’s Discretionary Early Release Science program of the James Webb Space Telescope, which will provide deep images and a high-resolution view with integral field spectroscopy.

Author(s):  
Geoff Cottrell

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.


2001 ◽  
Vol 18 (2) ◽  
pp. 182-185
Author(s):  
Geraint F. Lewis

AbstractThe true nature of dark matter in the universe still eludes us. This paper discusses a new test for the detection of stellar mass compact dark matter in galaxy clusters by observing its gravitational lensing influence on the surface brightness of giant luminous arcs. If dark matter is in the form of stellar mass compact objects, then the extremes of such variability are accessible to a monitoring campaign with the Hubble Space Telescope. With the advent of the Next Generation Space Telescope, cluster dark matter in the form of compact objects will induce a ubiquitous ‘shimmering’ of the giant arcs.


2020 ◽  
Vol 494 (1) ◽  
pp. L81-L85 ◽  
Author(s):  
E Vanzella ◽  
M Meneghetti ◽  
G B Caminha ◽  
M Castellano ◽  
F Calura ◽  
...  

ABSTRACT We discovered a strongly lensed (μ ≳ 40) Ly α emission at z = 6.629 (S/N ≃ 18) in the MUSE Deep Lensed Field (MDLF) targeting the Hubble Frontier Field (HFF) galaxy cluster MACS J0416. Dedicated lensing simulations imply that the Ly α emitting region necessarily crosses the caustic. The arc-like shape of the Ly α extends 3 arcsec on the observed plane and is the result of two merged multiple images, each one with a de-lensed Ly α luminosity L ≲ 2.8 × 1040 erg s−1 arising from a confined region (≲150 pc effective radius). A spatially unresolved Hubble Space Telescope(HST) counterpart is barely detected at S/N ≃ 2 after stacking the near-infrared bands, corresponding to an observed (intrinsic) magnitude m1500 ≳ 30.8 (≳35.0). The inferred rest-frame Ly α equivalent width is EW0 > 1120 Å if the IGM transmission is TIGM < 0.5. The low luminosities and the extremely large Ly α EW0 match the case of a Population III (Pop III) star complex made of several dozens stars (∼104 M⊙) that irradiate an H ii region crossing the caustic. While the Ly α and stellar continuum are among the faintest ever observed at this redshift, the continuum and the Ly α emissions could be affected by differential magnification, possibly biasing the EW0 estimate. The aforementioned tentative HST detection tends to favour a large EW0, making such a faint Pop III candidate a key target for the James Webb Space Telescope and Extremely Large Telescopes.


2015 ◽  
Vol 11 (A29B) ◽  
pp. 787-790
Author(s):  
S. H. Suyu ◽  
C. Grillo ◽  
P. Rosati

AbstractThe Frontier Fields cluster MACS J0416.1-2403 with its extensive imaging and spectroscopic data sets provides a great opportunity to study the mass distribution of the galaxy cluster and members, the high-redshift Universe and cosmology. By taking advantage of the observations in the 16 Hubble Space Telescope imaging bands of the Cluster Lensing And Supernova survey with Hubble (CLASH) survey and our large spectroscopic follow-up program with the VIsible Multi-Object Spectrograph (VIMOS) on the Very Large Telescope (VLT), we have been able to identify and obtain the spectroscopic redshifts of 10 important strong lensing systems in this cluster. Furthermore, we have selected and modeled the mass distribution of ~200 candidate cluster members residing in the inner regions of the cluster. We present the results on the model-predicted central mass profile and subhalo population, which are detailed in Grillo et al. (2015). Work is underway to quantify the effects of line-of-sight structures. These are essential elements to make progress in our understanding of the dark matter distribution in massive galaxy clusters and of the distant Universe within the current Frontier Fields initiative and before the advent of the James Webb Space Telescope.


2020 ◽  
Vol 500 (1) ◽  
pp. 40-53
Author(s):  
Fernanda Roman-Oliveira ◽  
Ana L Chies-Santos ◽  
Fabricio Ferrari ◽  
Geferson Lucatelli ◽  
Bruno Rodríguez Del Pino

ABSTRACT We explore the morphometric properties of a group of 73 ram-pressure stripping candidates in the A901/A902 multicluster system, at z∼ 0.165, to characterize the morphologies and structural evolution of jellyfish galaxies. By employing a quantitative measurement of morphometric indicators with the algorithm morfometryka on Hubble Space Telescope (F606W) images of the galaxies, we present a novel morphology-based method for determining trail vectors. We study the surface brightness profiles and curvature of the candidates and compare the results obtained with two analysis packages, morfometryka and iraf/ellipse on retrieving information of the irregular structures present in the galaxies. Our morphometric analysis shows that the ram-pressure stripping candidates have peculiar concave regions in their surface brightness profiles. Therefore, these profiles are less concentrated (lower Sérsic indices) than other star-forming galaxies that do not show morphological features of ram-pressure stripping. In combination with morphometric trail vectors, this feature could both help identify galaxies undergoing ram-pressure stripping and reveal spatial variations in the star formation rate.


2021 ◽  
Vol 162 (6) ◽  
pp. 271
Author(s):  
Guangwei Fu ◽  
Drake Deming ◽  
Erin May ◽  
Kevin Stevenson ◽  
David K. Sing ◽  
...  

Abstract Planets are like children with each one being unique and special. A better understanding of their collective properties requires a deeper understanding of each planet. Here we add the transit and eclipse spectra of hot-Jupiter WASP-74b into the ever growing data set of exoplanet atmosphere spectral library. With six transits and three eclipses using the Hubble Space Telescope and Spitzer Space Telescope (Spitzer), we present the most complete and precise atmospheric spectra of WASP-74b. We found no evidence for TiO/VO nor super-Rayleigh scattering reported in previous studies. The transit shows a muted water feature with strong Rayleigh scattering extending into the infrared. The eclipse shows a featureless blackbody-like WFC3/G141 spectrum and a weak methane absorption feature in the Spitzer 3.6 μm band. Future James Webb Space Telescope follow-up observations are needed to confirm these results.


2019 ◽  
Vol 490 (1) ◽  
pp. 1406-1414 ◽  
Author(s):  
Suresh Kumar ◽  
Rafael C Nunes ◽  
Santosh Kumar Yadav

ABSTRACT Dark matter (DM) as a pressureless perfect fluid provides a good fit of the standard Λ cold dark matter (ΛCDM) model to the astrophysical and cosmological data. In this paper, we investigate two extended properties of DM: a possible time dependence of the equation of state of DM via Chevallier–Polarski–Linder parametrization, wdm = wdm0 + wdm1(1 − a), and the constant non-null sound speed $\hat{c}^2_{\rm s,dm}$. We analyse these DM properties on top of the base ΛCDM model by using the data from Planck cosmic microwave background (CMB) temperature and polarization anisotropy, baryonic acoustic oscillations (BAOs), and the local value of the Hubble constant from the Hubble Space Telescope (HST). We find new and robust constraints on the extended free parameters of DM. The most tight constraints are imposed by CMB+BAO data, where the three parameters wdm0, wdm1, and $\hat{c}^2_{\rm s,dm}$ are, respectively, constrained to be less than 1.43 × 10−3, 1.44 × 10−3, and 1.79 × 10−6 at 95 per cent CL. All the extended parameters of DM show consistency with zero at 95 per cent CL, indicating no evidence beyond the CDM paradigm. We notice that the extended properties of DM significantly affect several parameters of the base ΛCDM model. In particular, in all the analyses performed here, we find significantly larger mean values of H0 and lower mean values of σ8 in comparison to the base ΛCDM model. Thus, the well-known H0 and σ8 tensions might be reconciled in the presence of extended DM parameters within the ΛCDM framework. Also, we estimate the warmness of DM particles as well as its mass scale, and find a lower bound: ∼500 eV from our analyses.


2015 ◽  
Vol 11 (S319) ◽  
pp. 127-127
Author(s):  
Inger Jørgensen ◽  
Scott Fisher ◽  
Charity Woodrum ◽  
Teiler Kwan ◽  
Jacob Bieker

AbstractWe present results on the stellar populations of bulge-dominated field galaxies at redshifts up to ≈1.0. The sample consists of non-cluster galaxies observed as part of the spectroscopic observations for the Gemini/HST Galaxy Cluster Project (GCP). Our preliminary results show that the bulge-dominated field galaxies contain younger stellar populations than cluster galaxies at similar redshifts. Future work will include photometry from Hubble Space Telescope and will be aimed at establishing the evolution of the sizes and the mass-to-light ratios for the field galaxies.


2001 ◽  
Vol 121 (1) ◽  
pp. 182-197 ◽  
Author(s):  
Debra Meloy Elmegreen ◽  
Michele Kaufman ◽  
Bruce G. Elmegreen ◽  
Elias Brinks ◽  
Curtis Struck ◽  
...  

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