Skip to main content

Astro Seminar

Astro Seminar

THE GALEX EXTRAGALACTIC SPECTRA DATA BASE

Abstract: 
 

We have matched objects in the Galaxy Evolution Explorer (GALEX) spectroscopic fields with publicly available ultraviolet, optical, and infrared surveys, to construct a photometric and spectroscopic catalog for non-stellar objects with GALEX spectroscopic counterparts. Of the total sample of GALEX spectra recorded in the database, approximately 20\% are determined to reliably correspond to non-stellar objects. These objects have been cross-matched with SDSS, WISE, and 2MASS photometric and spectroscopic survey catalogs, and VISTA and UKIRT near-IR catalogs where available, to construct spectral energy distributions (SED's) from the GALEX-FUV to WISE-w4 magnitudes for all non-stellar objects within the fields. Analysis of 209 fields with at least one object matched in SDSS give a total of 12,020 extragalactic objects, comprising 1974 known QSOs and AGNs, 2274 star-forming galaxies, 6327 quiescent spiral galaxies, and 386 elliptical galaxies.

 

Date:
Location:
CP179 and on zoom

Astro Seminar

THE GALEX EXTRAGALACTIC SPECTRA DATA BASE

Abstract: 
 

We have matched objects in the Galaxy Evolution Explorer (GALEX) spectroscopic fields with publicly available ultraviolet, optical, and infrared surveys, to construct a photometric and spectroscopic catalog for non-stellar objects with GALEX spectroscopic counterparts. Of the total sample of GALEX spectra recorded in the database, approximately 20\% are determined to reliably correspond to non-stellar objects. These objects have been cross-matched with SDSS, WISE, and 2MASS photometric and spectroscopic survey catalogs, and VISTA and UKIRT near-IR catalogs where available, to construct spectral energy distributions (SED's) from the GALEX-FUV to WISE-w4 magnitudes for all non-stellar objects within the fields. Analysis of 209 fields with at least one object matched in SDSS give a total of 12,020 extragalactic objects, comprising 1974 known QSOs and AGNs, 2274 star-forming galaxies, 6327 quiescent spiral galaxies, and 386 elliptical galaxies.

 

Date:
Location:
CP179 and on zoom

Astro Seminar

Molecular gas properties in young stellar clusters with a suppressed star cluster wind

In extremely compact and dense star-forming clouds a global star cluster wind could be suppressed. In this case the stellar feedback is unable to expel the leftover gas from the cluster. Young massive stars remain embedded into a dense residual gas and stir it moving in the gravitational well of the system. I shall present a self-consistent model for the molecular gas distribution in such young, enshrouded stellar clusters. It is assumed that the cloud collapse has been terminated and the star formation ceased when a balance between the turbulent pressure and gravity and between the turbulent energy dissipation and regeneration rates has been established. These conditions result in an equation that determines the residual gas density distribution that, in turn, allows one to obtain other characteristics of the leftover gas and the star formation efficiency. Finally, I shall confront this model with D1 molecular cloud and its embedded cluster in the dwarf spheroidal galaxy NGC 5253.

Date:
Location:
CP179 and on zoom

Astro Seminar

Molecular gas properties in young stellar clusters with a suppressed star cluster wind

In extremely compact and dense star-forming clouds a global star cluster wind could be suppressed. In this case the stellar feedback is unable to expel the leftover gas from the cluster. Young massive stars remain embedded into a dense residual gas and stir it moving in the gravitational well of the system. I shall present a self-consistent model for the molecular gas distribution in such young, enshrouded stellar clusters. It is assumed that the cloud collapse has been terminated and the star formation ceased when a balance between the turbulent pressure and gravity and between the turbulent energy dissipation and regeneration rates has been established. These conditions result in an equation that determines the residual gas density distribution that, in turn, allows one to obtain other characteristics of the leftover gas and the star formation efficiency. Finally, I shall confront this model with D1 molecular cloud and its embedded cluster in the dwarf spheroidal galaxy NGC 5253.

Date:
Location:
CP179 and on zoom

Astro Seminar

Reverberation mapping black hole accretion flows

Most of the power from an Active Galactic Nucleus is released close to the black hole, and thus studying the inner accretion flow, at the intersection of inflow and outflow, is essential for understanding how black holes grow and affect galaxy evolution. In the past decade, we have had a breakthrough in how we probe the inner accretion flow, through the discovery of X-ray Reverberation Mapping, where X-rays produced close to the black hole reverberate off inflowing gas. By measuring reverberation time delays, we can quantify the effects of strongly curved space time and the black hole spin, which is key for understanding how efficiently energy can be tapped from the accretion process. In this talk, I will give an overview of this field, and show how extending these spectral-timing techniques to transient accretion events like Tidal Disruption Events and black hole X-ray binaries is helping us probe the formation of X-ray coronae, jets and other relativistic outflows.

Date:
Location:
On-zoom

Astro Seminar

Reverberation mapping black hole accretion flows

Most of the power from an Active Galactic Nucleus is released close to the black hole, and thus studying the inner accretion flow, at the intersection of inflow and outflow, is essential for understanding how black holes grow and affect galaxy evolution. In the past decade, we have had a breakthrough in how we probe the inner accretion flow, through the discovery of X-ray Reverberation Mapping, where X-rays produced close to the black hole reverberate off inflowing gas. By measuring reverberation time delays, we can quantify the effects of strongly curved space time and the black hole spin, which is key for understanding how efficiently energy can be tapped from the accretion process. In this talk, I will give an overview of this field, and show how extending these spectral-timing techniques to transient accretion events like Tidal Disruption Events and black hole X-ray binaries is helping us probe the formation of X-ray coronae, jets and other relativistic outflows.

Date:
Location:
On-zoom

Astro Seminar

Title: THE ROLE OF SHOCKS IN THE EMISSION OF THE SINGLY IONIZED CARBON  IN GALAXIES

SUMMARY:

The fine structure [CII] line at 157.7um is considered a good tracer of star formation because it is unaffected by dust attenuation and it is bright enough to be detected in high-z galaxies. This happens because the singly ionized carbon C+ collisionally excited by the surrounding neutral atomic and molecular hydrogen acts as the main coolant for the molecular clouds heated by young bright stars in galaxies. In this talk I will present a few cases of nearby galaxies where shocks are instead the reason for the [CII] emission. In particular I will talk about galaxies where jets from the central AGN affect the interstellar medium at great distance from the nucleus and about a few other cases where shocks from galaxy interactions are at the origin of a [CII] emission excess.

Date:
Location:
CP179 and on-zoom

Astro Seminar

Title: THE ROLE OF SHOCKS IN THE EMISSION OF THE SINGLY IONIZED CARBON  IN GALAXIES

SUMMARY:

The fine structure [CII] line at 157.7um is considered a good tracer of star formation because it is unaffected by dust attenuation and it is bright enough to be detected in high-z galaxies. This happens because the singly ionized carbon C+ collisionally excited by the surrounding neutral atomic and molecular hydrogen acts as the main coolant for the molecular clouds heated by young bright stars in galaxies. In this talk I will present a few cases of nearby galaxies where shocks are instead the reason for the [CII] emission. In particular I will talk about galaxies where jets from the central AGN affect the interstellar medium at great distance from the nucleus and about a few other cases where shocks from galaxy interactions are at the origin of a [CII] emission excess.

Date:
Location:
CP179 and on-zoom