Search Publications
Young stellar population and ongoing star formation in the H II complex Sh2-252
Jose, Jessy; Samal, M. R.; Ojha, D. K. +7 more
In this paper, an extensive survey of the star-forming complex Sh2-252 has been undertaken with an aim to explore its hidden young stellar population as well as to understand the structure and star formation history for the first time. This complex is composed of five prominent embedded clusters associated with the subregions A, C, E, NGC 2175s an…
An extended main-sequence turn-off in the Small Magellanic Cloud star cluster NGC 411
Girardi, Léo; Chandar, Rupali; Marigo, Paola +8 more
Based on new observations with the Wide Field Camera 3 onboard the Hubble Space Telescope, we report the discovery of an extended main-sequence turn-off (eMSTO) in the intermediate-age star cluster NGC 411. This is the second case of an eMSTO being identified in a star cluster belonging to the Small Magellanic Cloud (SMC), after NGC 419. Despite t…
Resonant scattering in the Perseus Cluster: spectral model for constraining gas motions with Astro-H
Simionescu, A.; Sunyaev, R.; Sazonov, S. +6 more
X-ray spectra from cores of galaxy clusters can be strongly distorted by resonant scattering of line photons, affecting metal abundance and gas velocity measurements. We introduce simulated spectral models that take into account the resonant scattering effect, radial variations of thermodynamic properties of the hot gas, projection effects and sma…
The ACS LCID Project - VIII. The short-period Cepheids of Leo A
Skillman, Evan D.; Cole, Andrew A.; Tolstoy, Eline +9 more
We present the results of a new search for variable stars in the Local Group dwarf galaxy Leo A, based on deep photometry from the Advanced Camera for Surveys onboard the Hubble Space Telescope. We detected 166 bona fide variables in our field, of which about 60 per cent are new discoveries and 33 candidate variables. Of the confirmed variables, w…
HST/COS observations of a new population of associated QSO absorbers
Savage, B. D.; Narayanan, A.; Arav, N. +2 more
We present a sample of new population of associated absorbers, detected through Ne VIII λλ770, 780 absorption, in the Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS) spectra of intermediate-redshift (0.45 < z < 1.21) quasars (QSOs). Our sample comprised of total 12 associated Ne VIII systems detected towards eight lines of sig…
Filling the gap: a new class of old star cluster.
Usher, C.; Spitler, L. R.; Strader, J. +5 more
It is not understood whether long-lived star clusters possess a continuous range of sizes and masses (and hence densities) or if rather, they should be considered as distinct types with different origins. Utilizing the Hubble Space Telescope to measure sizes and long exposures on the Keck 10 m telescope to obtain distances, we have discovered the …
The ring nebula around the blue supergiant SBW1: pre-explosion snapshot of an SN 1987A twin
Filippenko, Alexei V.; Smith, Nathan; Ginsburg, Adam +2 more
SBW1 is a B-type supergiant surrounded by a ring nebula that is a nearby twin of SN 1987A's progenitor and its circumstellar ring. We present images and spectra of SBW1 obtained with the Hubble Space Telescope (HST), the Spitzer Space Telescope and Gemini South. HST images of SBW1 do not exhibit long Rayleigh-Taylor (RT) fingers, which are presume…
Stellar haloes of disc galaxies at z ∼ 1
Trujillo, Ignacio; Bakos, Judit
Taking advantage of the ultradeep near-infrared imaging obtained with the Hubble Space Telescope on the Hubble Ultra Deep Field, we detect and explore for the first time the properties of the stellar haloes of two Milky Way-like galaxies at z ∼ 1. We find that the structural properties of those haloes (size and shape) are similar to the ones found…
Nebular spectroscopy of the nearby Type IIb supernova 2011dh
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Cenko, S. Bradley +6 more
We present nebular spectra of the nearby Type IIb supernova (SN) 2011dh taken between 201 and 678 d after core collapse. At these late times, SN 2011dh exhibits strong emission lines including a broad and persistent Hα feature. New models of the nebular spectra confirm that the progenitor of SN 2011dh was a low-mass giant (M ≈ 13-15 M⊙)…
Constraining thermal dust emission in distant galaxies with number counts and angular power spectra
Bond, J. R.; Dunkley, J.; Addison, G. E.
We perform a joint fit to differential number counts from Spitzer's Multiband Imaging Photometer for Spitzer and Herschel's Spectral and Photometric Imaging Receiver (SPIRE) instruments, and angular power spectra of cosmic infrared background (CIB) anisotropies from SPIRE, Planck, the Atacama Cosmology Telescope and the South Pole Telescope, which…