Examinando por Autor "Treister, E."

Mostrando 1 - 3 de 3
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    BAT AGN Spectroscopic Survey. I. Spectral Measurements, Derived Quantities, and AGN Demographics
    (Institute of Physics Publishing, 2017-11) Koss, M.; Trakhtenbrot, B.; Ricci, C.; Lamperti, I.; Oh, K.; Berney, S.; Schawinski, K.; Baloković, M.; Baronchelli, L.; Crenshaw, D.M.; Fischer, T.; Gehrels, N.; Harrison, F.; Hashimoto, Y.; Hogg, D.; Ichikawa, K.; Masetti, N.; Mushotzky, R.; Sartori, L.; Stern, D.; Treister, E.; Ueda, Y.; Veilleux, S.; Winter, L.
    We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey. We analyze optical spectra of the majority of the detected AGNs (77%, 642/836)based on their 14-195 keV emission in the 70-month Swift-BAT all-sky catalog. This includes redshift determination, absorption and emission-line measurements, and black hole mass and accretion rate estimates for the majority of obscured and unobscured AGNs (74%, 473/642), with 340 measured for the first time. With ∼90% of sources at , the survey represents a significant advance in the census of hard X-ray-selected AGNs in the local universe. In this first catalog paper, we describe the spectroscopic observations and data sets, and our initial spectral analysis. The FWHMs of the emission lines show broad agreement with the X-ray obscuration (∼94%), such that Sy 1-1.8 have cm-2, and Seyfert 2 have cm-2. Seyfert 1.9, however, show a range of column densities. Compared to narrow-line AGNs in the SDSS, the X-ray-selected AGNs have a larger fraction of dusty host galaxies (), suggesting that these types of AGN are missed in optical surveys. Using the [O iii] λ5007/Hβ and [N ii] λ6583/Hα emission-line diagnostic, about half of the sources are classified as Seyferts; ∼15% reside in dusty galaxies that lack an Hβ detection, but for which the upper limits on line emission imply either a Seyfert or LINER, are in galaxies with weak or no emission lines despite high-quality spectra, and a few percent each are LINERS, composite galaxies, H ii regions, or in known beamed AGNs.
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    Ítem
    Discovery of Ram-pressure Stripped Gas around an Elliptical Galaxy in Abell 2670
    (IOP Publishing, 2017-05) Sheen, Y.-K.; Smith, R.; Jaffé, Y.; Kim, M.; Yi, S.K.; Duc, P.-A.; Nantais, J.; Candlish, G.; Demarco, R.; Treister, E.
    Studies of cluster galaxies are increasingly finding galaxies with spectacular one-sided tails of gas and young stars, suggestive of intense ram-pressure stripping. These so-called "jellyfish" galaxies typically have late-type morphology. In this paper, we present Multi Unit Spectroscopic Explorer (MUSE) observations of an elliptical galaxy in Abell 2670 with long tails of material visible in the optical spectra, as well as blobs with tadpole-like morphology. The spectra in the central part of the galaxy reveal a stellar component as well as ionized gas. The stellar component does not have significant rotation, while the ionized gas defines a clear star-forming gas disk. We argue, based on deep optical images of the galaxy, that the gas was most likely acquired during a past wet merger. It is possible that the star-forming blobs are also remnants of the merger. In addition, the direction and kinematics of the one-sided ionized tails, combined with the tadpole morphology of the star-forming blobs, strongly suggests that the system is undergoing ram pressure from the intracluster medium. In summary, this paper presents the discovery of a post-merger elliptical galaxy undergoing ram-pressure stripping
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    Ítem
    The ALMA Frontier Fields Survey: V. ALMA Stacking of Lyman-Break Galaxies in Abell 2744, Abell 370, Abell S1063, MACSJ0416.1-2403 and MACSJ1149.5+2223
    (EDP Sciences, 2020-01) Carvajal, R.; Bauer, F.; Bouwens, R.; Oesch, P.; Gonzalez-Lopez, J.; Anguita, T.; Aravena, M.; Demarco, R.; Guaita, L.; Infante, L.; Kim, S.; Kneiss., R.; Koekemoer, A.; Messias, H.; Treister, E.; Villard, E.; Zitrin, A.; Troncoso, P.
    Context. The Hubble Frontier Fields offer an exceptionally deep window into the high-redshift universe, covering a substantially larger area than the Hubble Ultra-Deep field at low magnification and probing 1-2 mag deeper in exceptional high-magnification regions. This unique parameter space, coupled with the exceptional multi-wavelength ancillary data, can facilitate for useful insights into distant galaxy populations. Aims. We aim to leverage Atacama Large Millimetre Array (ALMA) band 6 (≈263 GHz) mosaics in the central portions of five Frontier Fields to characterize the infrared (IR) properties of 1582 ultraviolet (UV)-selected Lyman-Break Galaxies (LBGs) at redshifts of z  ∼  2-8. We investigated individual and stacked fluxes and IR excess (IRX) values of the LBG sample as functions of stellar mass (M⋆ ), redshift, UV luminosity and slope β, and lensing magnification. Methods. LBG samples were derived from color-selection and photometric redshift estimation with Hubble Space Telescope photometry. Spectral energy distributions -templates were fit to obtain luminosities, stellar masses, and star formation rates for the LBG candidates. We obtained individual IR flux and IRX estimates, as well as stacked averages, using both ALMA images and u-v visibilities. Results. Two (2) LBG candidates were individually detected above a significance of 4.1-σ, while stacked samples of the remaining LBG candidates yielded no significant detections. We investigated our detections and upper limits in the context of the IRX-M⋆ and IRX-β relations, probing at least one dex lower in stellar mass than past studies have done. Our upper limits exclude substantial portions of parameter space and they are sufficiently deep in a handful of cases to create mild tension with the typically assumed attenuation and consensus relations. We observe a clear and smooth trend between M⋆ and β, which extends to low masses and blue (low) β values, consistent with expectations from previous works.