K. Boutsia
A5001676664- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Astro and Planetary Science
- Calibration and Measurement Techniques
- Cosmology and Gravitation Theories
- CCD and CMOS Imaging Sensors
- Scientific Research and Discoveries
- Remote Sensing in Agriculture
- Computational Physics and Python Applications
- Advanced Image Processing Techniques
- Seismic Imaging and Inversion Techniques
- Geophysics and Gravity Measurements
- Molecular Spectroscopy and Structure
- Atmospheric Ozone and Climate
- Time Series Analysis and Forecasting
- Neutrino Physics Research
Cerro Tololo Inter-American Observatory
2024-2025
Las Campanas Observatory
2017-2024
Carnegie Institution for Science
2018-2022
Carnegie Observatories
2018
Astronomical Observatory of Rome
2009-2017
National Institute for Astrophysics
2009-2016
University of Arizona
2012-2013
Las Cumbres Observatory Global Telescope Network
2012
European Southern Observatory
2007-2009
Excellence Cluster Universe
2009
On 2017 August 17, gravitational waves were detected from a binary neutron star merger, GW170817, along with coincident short gamma-ray burst, GRB170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, and infrared light curves SSS17a extending 10.9 hours to 18 days post-merger. constrain radioactively-powered resulting ejection neutron-rich material. The fast rise curves, subsequent...
Distant quasars are unique tracers to study the formation of earliest supermassive black holes (SMBHs) and history cosmic reionization. Despite extensive efforts, only two have been found at $z\ge7.5$, due a combination their low spatial density high contamination rate in quasar selection. We report discovery luminous $z=7.642$, J0313$-$1806, most distant yet known. This has bolometric luminosity $3.6\times10^{13} L_\odot$. Deep spectroscopic observations reveal SMBH with mass $(1.6\pm0.4)...
On 2017 August 17, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of binary neutron star gravitational wave event GW170817. We report time-series spectroscopy SSS17a from 11.75 hours until 8.5 days after merger. Over first hour observations ejecta rapidly expanded and cooled. Applying blackbody fits to spectra, we measure photosphere cooling $11,000^{+3400}_{-900}$ K $9300^{+300}_{-300}$ K, determine a photospheric velocity roughly 30% speed light. The...
The galaxy stellar mass function (GSMF) at high-z provides key information on star-formation history and assembly in the young Universe. We aimed to use unique combination of deep optical/NIR/MIR imaging provided by HST, Spitzer VLT CANDELS-UDS, GOODS-South, HUDF fields determine GSMF over redshift range 3.5<z<7.5. utilised HST WFC3/IR NIR from CANDELS HUDF09, reaching H~27-28.5 a total area 369 arcmin2, with associated ACS optical data, IRAC SEDS programme, Y K-band Hawk-I images HUGS...
We present the public release of stellar mass catalogs for GOODS-S and UDS fields obtained using some deepest near-IR images available, achieved as part Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey project. combine effort from 10 different teams, who computed masses same photometry redshifts. Each team adopted their preferred fitting code, assumptions, priors, parameter grid. The combination results underlying isochrones reduces systematics associated with code other...
Photons from a gravitational wave event Two neutron stars merging together generate signal and have also been predicted to emit electromagnetic radiation. When the GW170817 was detected, astronomers rushed search for source using conventional telescopes (see Introduction by Smith). Coulter et al. describe how One-Meter Two-Hemispheres (1M2H) collaboration first locate source. Drout present 1M2H measurements of its optical infrared brightness, Shappee report their spectroscopy event, which is...
The GLASS James Webb Space Telescope Early Release Science (hereafter GLASS-JWST-ERS) Program will obtain and make publicly available the deepest extragalactic data of ERS campaign. It is primarily designed to address two key science questions, namely, "what sources ionized universe when?" "how do baryons cycle through galaxies?", while also enabling a broad variety first look scientific investigations. In primary mode, it NIRISS NIRSpec spectroscopy galaxies lensed by foreground Hubble...
We study the star formation and mass assembly process of 0.3<=z<2.5 galaxies using their IR emission from MIPS 24um band. used an updated version GOODS-MUSIC catalog, extended by addition mid-IR fluxes. compared two different estimators Star Formation Rate: total infrared derived 24um, estimated both synthetic empirical templates, multiwavelength fit to full galaxy SED. For estimates, we computed SFR Density Specific SFR. The tracers are roughly consistent, given uncertainties involved....
We present the final results from our ultra-deep spectroscopic campaign with FORS2 at ESO/VLT for confirmation of z~7 "z--band dropout" candidates selected VLT/Hawk-I imaging survey over three independent fields. In particular we report on two newly discovered galaxies redshift ~6.7 in NTT deep field: both show a Ly-alpha emission line rest-frame EWs order 15-20 A and luminosities 2-4 X 10^{42} erg/s. also observations sample i-dropout galaxies, which set solid upper limit fraction...
As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study physical properties of several planets in parallel. In this paper, we image all four at H-band and 3.3 microns with new LBT adaptive optics PISCES, LBTI/LMIRCam. Our images offer an unprecedented view allowing us obtain H 3.3$ micron photometry innermost (for first time) put strong upper-limits on presence hypothetical fifth companion. We find that are unexpectedly bright compared equilibrium...
Nearly every massive galaxy harbors a supermassive black hole (SMBH) in its nucleus. SMBH masses are millions to billions $M_{\odot}$, and they correlate with properties of spheroids their host galaxies. While the growth channels, mergers gas accretion, well established, origin remains uncertain: could have either emerged from "seeds" ($10^5-10^6 M_{\odot}$) formed by direct collapse clouds early Universe or smaller ($100 holes, end-products first stars. The latter channel would leave behind...
We present ultradeep optical spectroscopy obtained with FORS2 on VLT of seven Lyman-break galaxy (LBG) candidates at z>6.5 selected in the GOODS-S field from Hawk-I/VLT and WFC3/HST imaging. For one we detect a low significance emission line (S/N< 7), located 9691.5 +/- 0.5A flux 3.4 x 10^(-18)erg/cm^2/s. If identified as Lyman alpha, it places LBG redshift z=6.972+/- 0.002, rest-frame equivalent width EW}=13A. Using Monte Carlo simulations conservative EW distribution functions 2<z<6,...
We use ultra-deep ultraviolet VLT/VIMOS intermediate-band and VLT/FORS1 narrowband imaging in the GOODS Southern field to derive limits on distribution of escape fraction (fesc) ionizing radiation for L ⩾ L*z=3 Lyman-break galaxies (LBGs) at redshift 3.4–4.5. Only one LBG, z = 3.795, is detected its Lyman continuum (LyC; S/N ≃ 5.5), highest galaxy currently known with a direct detection. Its morphology quite compact (Reff 0.8 kpc physical). Three out seven active galactic nuclei are also...
We report the spectroscopic confirmation of two Lyman break galaxies at redshift >7. The were observed as part an ultra-deep campaign with FORS2 ESO/VLT for z ≃ 7 "z-band dropout" candidates selected from our VLT/Hawk-I imaging survey. Both show a prominent emission line 9735 Å and 9858 Å, respectively: lines have fluxes ∼(1.6–1.2) × 10−17 erg s−1 cm−2 exhibit sharp decline on blue side tail red side. asymmetry is quantitatively comparable to in ∼ 6 Lyα lines, where absorption by neutral...
We present detection and analysis of faint X-ray sources in the Chandra deep field south (CDFS) using 4 Msec observation adopting a new algorithm, based on targeted search at position known high-z galaxies. This optimized technique results identification 54 z>3 AGNs, 29 which are detections. Applying stringent completeness criteria, we derive AGN luminosity functions redshift bins 3-4, 4-5 >5.8 for 42.753 (18+17-10%). Their optical counterparts not strongly reddened thus conclude that...
We used Early Release Science (ERS) observations taken with the Wide Field Camera 3 (WFC3) in GOODS-S field to study galaxy stellar mass function (GSMF) at 0.6<=z<4.5. Deep WFC3 near-IR data (for Y as faint 27.3, J and H 27.4 AB mag 5 sigma), well deep Ks (as 25.5 sigma) Hawk-I band data, provide an exquisite set which determine unprecedented way low-mass end of GSMF, allowing accurate probe masses low M~7.6 10^9 Msun z~3. Although area is relatively small (~33 arcmin^2), we found...
Aims. We present the first public release of photometric redshifts, galaxy rest frame properties and associated magnification values in cluster parallel pointings two Frontier Fields, Abell-2744 MACS-J0416. The released catalogues aim to provide a reference for future investigations extragalactic populations these legacy fields: from lensed high-redshift galaxies members themselves.
We present T-PHOT, a publicly available software aimed at extracting accurate photometry from low-resolution images of deep extragalactic fields, where the blending sources can be serious problem for and unbiased measurement fluxes colours. T-PHOT has been developed within ASTRODEEP project it considered as next generation to TFIT, providing significant improvements above other similar codes. gathers data high-resolution image region sky, uses obtain priors photometric analysis lower...
Context. The Frontier Fields survey is a pioneering observational program aimed at collecting photometric data, both from space (Hubble Space Telescope and Spitzer Telescope) ground-based facilities (VLT Hawk-I), for six deep fields pointing clusters of galaxies nearby parallel fields, in wide range passbands. analysis these data natural outcome the Astrodeep project, an EU collaboration developing methods tools extragalactic photometry creating valuable public catalogues.
We present the discovery and early evolution of ASASSN-19bt, a tidal disruption event (TDE) discovered by All-Sky Automated Survey for Supernovae (ASAS-SN) at distance $d\simeq115$ Mpc first TDE to be detected TESS. As is located in TESS Continuous Viewing Zone, our dataset includes 30-minute cadence observations starting on 2018 July 25, we precisely measure that begins brighten $\sim8.3$ days before its discovery. Our also 18 epochs Swift UVOT XRT observations, 2 XMM-Newton 13...
Abstract The study of the space density bright active galactic nuclei (AGNs) at z > 4 has been subject to extensive effort given its importance in estimation cosmological ionizing emissivity and growth supermassive black holes. In this context we have recently derived high densities AGNs ∼ −25 < M 1450 −23 Cosmic Evolution Survey (COSMOS) field from a spectroscopically complete sample. present paper attempt extend knowledge AGN fainter magnitudes (−22.5 −18.5) 6.1 redshift interval by...
<title>Abstract</title> Red Supergiants (RSGs) are cool, evolved massive stars in their final evolutionary stage before exploding as a supernova [1, 2]. However, the evolution and fate of most luminous RSGs is uncertain. Observational evidence for warm, post-RSG objects [3] lack progenitors [4] suggest blueward evolution. Since 1980s, WOH G64 has been considered extreme RSG Large Magellanic Cloud given its outstanding size, luminosity, mass-loss rate [5–7]. Here we report sudden, yet smooth...
Context. Study of the dust extinction in high-redshift galaxies is fundamental to obtaining an estimate corrected star formation rate density (SFRD) and put constraints on galaxy evolution models.
The reionization of the Universe is one most important topics present day astrophysical research. plausible candidates for process are star-forming galaxies, which according to predictions majority theoretical and semi-analytical models should dominate HI ionizing background at z~3. We aim measuring Lyman continuum escape fraction, key parameters compute contribution galaxies UV background. have used ultra-deep U-band imaging (U=30.2mag 1sigma) by LBC/LBT in CANDELS/GOODS-North field, as...