Alessandra Aloisi
A5063890987- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Calibration and Measurement Techniques
- Photocathodes and Microchannel Plates
- Atmospheric Ozone and Climate
- Spectroscopy and Laser Applications
- Adaptive optics and wavefront sensing
- Dark Matter and Cosmic Phenomena
- CCD and CMOS Imaging Sensors
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Geomagnetism and Paleomagnetism Studies
- Particle Detector Development and Performance
- Atmospheric and Environmental Gas Dynamics
- Astrophysics and Cosmic Phenomena
- Career Development and Diversity
- Nuclear Physics and Applications
- Scientific Measurement and Uncertainty Evaluation
- Atomic and Molecular Physics
Space Telescope Science Institute
2015-2024
Michigan Science Center
2011-2015
University College London
2011
European Space Agency
2005-2008
Johns Hopkins University
2003-2004
Osservatorio astronomico di Bologna
1999-2001
University of Bologna
1999
The Legacy ExtraGalactic UV Survey (LEGUS) is a Cycle 21 Treasury program on the Hubble Space Telescope aimed at investigation of star formation and its relation with galactic environment in nearby galaxies, from scales individual stars to those ∼kiloparsec-size clustered structures. Five-band imaging near-ultraviolet I band Wide-Field Camera 3 (WFC3), plus parallel optical Advanced for Surveys (ACS), being collected selected pointings 50 galaxies within local 12 Mpc. filters used...
We have analyzed FUSE (905–1187 Å) spectra of a sample 16 local starburst galaxies. These galaxies cover almost three orders magnitude in star-formation rates and over two stellar mass. Absorption features from the stars interstellar medium are observed all spectra. The strongest absorption generally blue-shifted by ∼ 50–300 km s−1, implying ubiquitous presence starburst-driven galactic winds this sample. outflow velocites increase with both rate per unit mass, consistent wind, driven...
A candidate diffuse stellar substructure was previously reported in the halo of nearby dwarf starburst galaxy NGC 4449 by Karachentsev et al. We map and analyze this feature using a unique combination deep integrated-light images from Black Bird 0.5-meter telescope, high-resolution wide-field 8-meter Subaru which resolve nebulosity into stream red giant branch stars, confirm its physical association with 4449. The properties imply massive spheroidal progenitor, after complete disruption will...
We report the large effort which is producing comprehensive high-level young star cluster (YSC) catalogues for a significant fraction of galaxies observed with Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. present methodology developed to extract positions, verify their genuine nature, produce multiband photometry (from NUV NIR), and derive physical properties via spectral energy distribution fitting analyses. use nearby spiral galaxy NGC628 as test case demonstrating...
We present and describe the astro-photometric catalog of more than 800,000 sources found in Hubble Tarantula Treasury Project (HTTP). HTTP is a Space Telescope (HST) program designed to image entire 30 Doradus region down sub-solar (~0.5 solar masses) mass regime using Wide Field Camera 3 (WFC3) Advanced for Surveys (ACS). observed near ultraviolet (F275W, F336W), optical (F555W, F658N, F775W), infrared (F110W, F160W) wavelengths. The stellar photometry was measured point-spread function...
Far-ultraviolet (FUV; ~1200-2000 angstroms) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch JWST will soon usher in new era, pushing the UV spectroscopic frontier higher redshifts than ever before, however, its success hinges comprehensive star populations gas conditions that power observed spectral features. This requires level detail is only...
Abstract We report the results of analyses galactic outflows in a sample 45 low-redshift starburst galaxies COS Legacy Archive Spectroscopic SurveY (CLASSY), augmented by five additional similar starbursts with Cosmic Origins Spectrograph (COS) data. The are traced blueshifted absorption lines metals spanning wide range ionization potential. high quality and broad spectral coverage CLASSY data enable us to disentangle due static interstellar medium (ISM) from that outflows. further use...
Abstract In the current JWST era, rest-frame UV spectra play a crucial role in enhancing our understanding of interstellar medium (ISM) and stellar properties first galaxies epoch reionization ( z > 6). Here, we compare well-known reliable optical diagrams sensitive to main ionization source (i.e., star formation, SF; active galactic nuclei, AGN; shocks) counterparts proposed literature—the so-called “UV–BPT diagrams”—using HST COS Legacy Archive Spectroscopic SurveY (CLASSY), which is...
We present new V- and I-band HST ACS photometry of I Zw 18, the most metal-poor blue compact dwarf (BCD) galaxy in nearby universe. It has been argued past that 18 is a very young system started forming stars only ≲500 Myr ago, but other work hinted older (≳1 Gyr) red giant branch (RGB) may also exist. Our data, once combined with archival provide deep uncontaminated optical color-magnitude diagram (CMD) now strongly indicates an RGB. The RGB tip (TRGB) magnitude yields distance modulus (m -...
Heckman et al. (2005) used the Galaxy Evolution Explorer (GALEX) UV imaging survey to show that there exists a rare population of nearby compact UV-luminous galaxies (UVLGs) closely resembles high redshift Lyman break (LBGs). We present HST images in UV, optical, and Ha, resimulate them at depth resolution GOODS/UDF fields morphologies UVLGs are also similar those LBGs. Our sample 8 LBG analogs thus provides detailed insight into connection between star formation morphology. Faint tidal...
We present an investigation of the relationship between giant molecular cloud (GMC) properties and associated stellar clusters in nearby flocculent galaxy NGC 7793. combine star cluster catalogue from HST LEGUS (Legacy ExtraGalactic UV Survey) programme with 15 pc resolution ALMA CO(2–1) observations. find a strong spatial correlation young GMCs such that all still GMC are younger than 11 Myr display median age 2 Myr. The distribution increases gradually as cluster–GMC distance increases,...
We present a study of the recent star formation 30 Doradus in Large Magellanic Cloud (LMC) using panchromatic imaging survey Hubble Tarantula Treasury Project (HTTP). In this paper we focus on stars within 20 pc center massive ionizing cluster Doradus, NGC 2070. recovered history by comparing deep optical and NIR color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated latest PARSEC models, which include all stellar phases from pre-main sequence to post- main sequence....
We present a study of the spatial distribution stellar cluster populations in star-forming galaxy NGC 628. Using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from Treasury Program LEGUS (Legacy ExtraGalactic Survey), we have identified 1392 potential young ( Myr) clusters within using combination visual inspection automatic selection. investigate clustering these quantify strength change with scale two-point correlation function. also how image boundary conditions dust...
We present the star cluster catalogs for 17 dwarf and irregular galaxies in $HST$ Treasury Program "Legacy ExtraGalactic UV Survey" (LEGUS). Cluster identification photometry this subsample are similar to that of entire LEGUS sample, but special methods were developed provide robust with accurate fluxes due low statistics. The colors ages largely consistent two widely used aperture corrections, a significant fraction clusters more compact than average training cluster. However, ensemble...
Abstract The Cosmic Origins Spectrograph (COS) Legacy Archive Spectroscopic SurveY (CLASSY) provides the first high-resolution spectral catalog of 45 local high- z analogs in ultraviolet (UV; 1200–2000 Å) to investigate their stellar and gas properties. Here we present a toolkit UV interstellar medium (ISM) diagnostics, analyzing main emission lines CLASSY spectra (N iv ] λ 1483,87, C λλ 1548,51, He ii 1640, O iii 1661,6, Si 1883,92, 1907,9). Specifically, our aim is provide accurate...
Abstract Ly α line profiles are a powerful probe of interstellar medium (ISM) structure, outflow speed, and Lyman-continuum escape fraction. In this paper, we present the Cosmic Origins Spectrograph (COS) Legacy Archive Spectroscopic SurveY, sample rich in spectroscopic analogs reionization-era galaxies. A large fraction spectra show complex profile, consisting double-peaked emission profile bottom damped, absorption trough. Such reveal an inhomogeneous ISM. We successfully fit damped...
The star formation history in I Zw 18 has been inferred from Hubble Space Telescope Wide Field Planetary Camera 2 archival data. This is done by comparing the derived V, B-V and V-I color-magnitude diagrams luminosity functions with synthetic ones, based on various sets of stellar evolutionary tracks. At a distance 10 Mpc, stars resolved field allow for look-back time up to 1 Gyr. We find that main body not experiencing its first episode formation. Instead, it forming over last 0.5–1 Gyr, at...
We have reanalyzed FUSE data and obtained new Chandra observations of Haro 11, a local (DL = 88 Mpc) UV luminous galaxy. 11 has far-UV luminosity (1010.3 L☉), surface brightness (109.4 L☉ kpc-2), star formation rate (SFR), metallicity similar to those observed in Lyman-break galaxies (LBGs). show that extended soft thermal (kT ~ 0.68 keV) X-ray emission size which scales with the physical properties (e.g., SFR, stellar mass) host An enhanced α/Fe ratio ~4 relative solar abundance suggests...
The Hubble Tarantula Treasury Project (HTTP) is an ongoing panchromatic imaging survey of stellar populations in the Nebula Large Magellanic Cloud that reaches into sub-solar mass regime (<0.5 M☉). HTTP utilizes capability Space Telescope to operate Advanced Camera for Surveys and Wide Field 3 parallel study this remarkable region near-ultraviolet, optical, near-infrared spectral regions, including narrow-band Hα images. combination all these bands provides a unique multi-band view....
The nearby dwarf starburst galaxy NGC 5253 hosts a number of young, massive star clusters, the two youngest which are centrally concentrated and surrounded by thermal radio emission (the "radio nebula"). To investigate role these clusters in energetics, we combine new archival Hubble Space Telescope images with wavelength coverage from 1500 Å to 1.9 μm 13 filters. These include Hα, Pβ, Pα, imaging Treasury Program LEGUS (Legacy Extragalactic UV Survey). extraordinarily well-sampled spectral...
This is the first in a series of three papers describing project with Cosmic Origins Spectrograph on Hubble Space Telescope to measure abundances neutral interstellar medium (ISM) sample 9 nearby star-forming galaxies. The goal assess (in)homogeneities multiphase ISM galaxies where bulk metals can be hidden phase, yet metallicity inferred from ionized gas HII regions. sample, spanning wide range physical properties, date best suited investigate behavior at redshift z=0. absorption lines were...
The morphology of HII regions around young star clusters provides insight into the timescales and physical processes that clear a cluster's natal gas. We study ~700 (<10Myr) in three nearby spiral galaxies (NGC 7793, NGC 4395, 1313) using Hubble Space Telescope (HST) imaging from LEGUS (Legacy ExtraGalactic Ultraviolet Survey). Clusters are classified by their H$\alpha$ (concentrated, partially exposed, no-emission) whether they have neighboring (which could affect clearing timescales)....
We report on the study of interstellar extinction across Tarantula nebula (30 Doradus), in Large Magellanic Cloud, using observations from Hubble Treasury Project 0.3 - 1.6 micron range. The considerable and patchy inside causes about 3500 red clump stars to be scattered along reddening vector colour-magnitude diagrams, thereby allowing an accurate determination slope all bands. measured is remarkably steeper bands than Galactic diffuse medium. At optical wavelengths, larger ratio...
Abstract The COS Legacy Archive Spectroscopic SurveY (CLASSY) is designed to provide the community with a spectral atlas of 45 nearby star-forming galaxies that were chosen cover similar properties those seen at high z ( > 6). prime high-level science product CLASSY accurately coadded UV spectra, ranging from ∼1000 2000 Å, derived combination archival and new data obtained HST’s Cosmic Origins Spectrograph (COS). This paper details multistage technical processes creating this...