Velocity Segregation and Systematic Biases in Velocity Dispersion Estimates with the SPT-GMOS Spectroscopic Survey

Bayliss, M.; Zengo, K.; Ruel, J.; Benson, B. A.; Bleem, L. E.; Bocquet, S.; Bulbul, Esra; Brodwin, M.; Capasso, R.; Chiu, I-Non; McDonald, Michael; Rapetti, David; Saro, A.; Stalder, B.; Stark, A. A.; Strazzullo, V.; Stubbs, C. W.; Zenteno, A.

doi:10.3847/1538-4357/aa607c

“…bution. This is consistent with expectations (see Ruel et al 2014;Bayliss et al 2017). We also analyze the distribution of cluster member galaxies in velocity-radius phase space by distinguishing passive (orange) from [OII]-emitting (purple) galaxies.…”

Section: Velocity-radius Diagrams For a Stacked Clustersupporting

confidence: 87%

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg² SPT-SZ Survey

Khullar

¹

,

Bleem

²

,

Bayliss

³

et al. 2018

ApJ

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We present spectroscopic confirmation of five galaxy clusters at 1.25 < z < 1.5, discovered in the 2500 deg 2 South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. These clusters, taken from a mass-limited sample with a nearly redshift independent selection function, have multi-wavelength follow-up imaging data from the X-ray to near-IR, and currently form the most homogeneous massive high-redshift cluster sample known. We identify 44 member galaxies, along with 25 field galaxies, among the five clusters, and describe the full set of observations and data products from Magellan/LDSS3 multi-object spectroscopy of these cluster fields. We briefly describe the analysis pipeline, and present ensemble analyses of cluster member galaxies that demonstrate the reliability of the measured redshifts. We report z = 1.259, 1.288, 1.316, 1.401 and 1.474 for the five clusters from a combination of absorption-line (Ca II H&K doublet -λλ3968,3934Å) and emission-line ([OII] λλ3727,3729Å) spectral features. Moreover, the calculated velocity dispersions yield dynamical cluster masses in good agreement with SZ masses for these clusters. We discuss the velocity and spatial distributions of passive and [OII]-emitting galaxies in these clusters, showing that they are consistent with velocity segregation and biases observed in lower redshift SPT clusters. We identify modest [OII] emission and pronounced CN and Hδ absorption in a stacked spectrum of 28 passive galaxies with Ca II H&K-derived redshifts. This work increases the number of spectroscopically-confirmed SZ-selected galaxy clusters at z > 1.25 from three to eight, 2 KHULLAR ET AL. further demonstrating the efficacy of SZ selection for the highest redshift massive clusters, and enabling detailed study of these systems.

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“…These competing effects are subject to observational selection in magnitude, colour, galaxy type, star formation activity and aperture which need to be addressed with larger sample size. There is growing observational evidence that velocity bias is a function of the aforementioned selection variables (e.g., Guo et al 2015a;Barsanti et al 2016;Bayliss et al 2017).…”

Section: Velocity Biasmentioning

confidence: 99%

The XXL Survey

Farahi

¹

,

Guglielmo

²

,

Evrard

³

et al. 2018

A&A

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Context. An X-ray survey with the XMM-Newton telescope, XMM-XXL, has identified hundreds of galaxy groups and clusters in two 25 deg2 fields. Combining spectroscopic and X-ray observations in one field, we determine how the kinetic energy of galaxies scales with hot gas temperature and also, by imposing prior constraints on the relative energies of galaxies and dark matter, infer a power-law scaling of total mass with temperature. Aims. Our goals are: i) to determine parameters of the scaling between galaxy velocity dispersion and X-ray temperature, T300 kpc, for the halos hosting XXL-selected clusters, and; ii) to infer the log-mean scaling of total halo mass with temperature, ⟨lnM200 | T300 kpc, z⟩. Methods. We applied an ensemble velocity likelihood to a sample of >1500 spectroscopic redshifts within 132 spectroscopically confirmed clusters with redshifts z < 0.6 to model, ⟨lnσgal | T300 kpc, z⟩, where σgal is the velocity dispersion of XXL cluster member galaxies and T300 kpc is a 300 kpc aperture temperature. To infer total halo mass we used a precise virial relation for massive halos calibrated by N-body simulations along with a single degree of freedom summarising galaxy velocity bias with respect to dark matter. Results. For the XXL-N cluster sample, we find σgal ∝ T300 kpc0.63±0.05, a slope significantly steeper than the self-similar expectation of 0.5. Assuming scale-independent galaxy velocity bias, we infer a mean logarithmic mass at a given X-ray temperature and redshift, 〈ln(E(z)M200/1014 M⊙)|T300 kpc, z〉 = πT + αT ln (T300 kpc/Tp) + βT ln (E(z)/E(zp)) using pivot values kTp = 2.2 keV and zp = 0.25, with normalization πT = 0.45 ± 0.24 and slope αT = 1.89 ± 0.15. We obtain only weak constraints on redshift evolution, βT = −1.29 ± 1.14. Conclusions. The ratio of specific energies in hot gas and galaxies is scale dependent. Ensemble spectroscopic analysis is a viable method to infer mean scaling relations, particularly for the numerous low mass systems with small numbers of spectroscopic members per system. Galaxy velocity bias is the dominant systematic uncertainty in dynamical mass estimates.

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“…Detailed properties of the SPT clusters are discussed in [35]. Their redshifts have been obtained using survey data as well as pointed spectroscopic and photometric observations [36][37][38][39][40]. The first step in estimating the gas mass fraction consists of determining the total mass of the cluster at R 500 , known as M 500 .…”

Section: For Spt-sz Samplementioning

confidence: 99%

A model-independent test of the evolution of gas depletion factor for SPT-SZ and Planck ESZ clusters

Bora

¹

,

Desai

²

2021

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The gas mass fraction in galaxy clusters has been widely used to determine cosmological parameters. This method assumes that the ratio of the cluster gas mass fraction to the cosmic baryon fraction ($$\gamma (z)$$ γ ( z ) ) is constant as a function of redshift. In this work, we look for a time evolution of $$\gamma (z)$$ γ ( z ) at $$R_{500}$$ R 500 by using both the SPT-SZ and Planck Early SZ (ESZ) cluster data, in a model-independent fashion without any explicit dependence on the underlying cosmology. For this calculation, we use a non-parametric functional form for the Hubble parameter obtained from Gaussian Process regression using cosmic chronometers. We parameterize $$\gamma (z)$$ γ ( z ) as: $$\gamma (z)= \gamma _0(1+\gamma _1 z)$$ γ ( z ) = γ 0 ( 1 + γ 1 z ) to constrain the redshift evolution. We find contradictory results between both the samples. For SPT-SZ, $$\gamma (z)$$ γ ( z ) decreases as a function of redshift (at more than 5$$\sigma $$ σ ), whereas a positive trend with redshift is found for Planck ESZ data (at more than 4$$\sigma $$ σ ). We however find that the $$\gamma _1$$ γ 1 values for a subset of SPT-SZ and Planck ESZ clusters between the same redshift interval agree to within $$1\sigma $$ 1 σ . When we allow for a dependence on the halo mass in the evolution of the gas depletion factor, the $$4-5\sigma $$ 4 - 5 σ discrepancy reduces to $$2\sigma $$ 2 σ .

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Velocity Segregation and Systematic Biases in Velocity Dispersion Estimates with the SPT-GMOS Spectroscopic Survey

Cited by 26 publications

References 116 publications

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg² SPT-SZ Survey

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg² SPT-SZ Survey

The XXL Survey

A model-independent test of the evolution of gas depletion factor for SPT-SZ and Planck ESZ clusters

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Velocity Segregation and Systematic Biases in Velocity Dispersion Estimates with the SPT-GMOS Spectroscopic Survey

Cited by 26 publications

References 116 publications

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg2 SPT-SZ Survey

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg2 SPT-SZ Survey

The XXL Survey

A model-independent test of the evolution of gas depletion factor for SPT-SZ and Planck ESZ clusters

Contact Info

Product

Resources

About

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg² SPT-SZ Survey

Spectroscopic Confirmation of Five Galaxy Clusters at z > 1.25 in the 2500 deg² SPT-SZ Survey