alberto conti - Academia.edu (original) (raw)
Papers by alberto conti
GALEX-SDSS Crossmatch In The Database
ABSTRACT
Astronomical Visualization for Education
ABSTRACT
Angular Clustering and the Role of Photometric Redshifts
With the new generation of deep, space-based imaging surveys, such as those proposed for the SNAP... more With the new generation of deep, space-based imaging surveys, such as those proposed for the SNAP satellite, we will have an unprecedented opportunity to characterize the evolution of the clustering properties of galaxies across a wide range of look-back times. We consider ...
Everybody Has a Sky
Many astronomers and amateurs have noted that upon discovery of Google Earth, after its release i... more Many astronomers and amateurs have noted that upon discovery of Google Earth, after its release in mid-2005, they thought it would be a great interface for astronomical data. We came to the Sky project along separate trajectories, but by January 2006 we had joined forces and engaged the GoogleEarth team in Mountain View, CA. After an initial high energy meeting with Google, in 2006, we began experiments using the GoogleEarth technology and protocols, specifically Keyhole Markup Language (KML), and designed a mechanism for placing HST press release images and ancillary information into the Google Earth interface. We will briefly describe our primary role in providing HST Press Release images and supplementary information on the images for the Sky interface. We also have explored catalog services from custom analysis provided through the new Hubble Legacy Archive. We also will mention our plans for interaction with the Virtual Observatory. We also have worked with colleagues at the Un...
The Astronomer's HR diagram
Most people who've taken an astronomy course are familiar with the Hertzsprung-Russell diagra... more Most people who've taken an astronomy course are familiar with the Hertzsprung-Russell diagram. It was developed to show the relationships between the temperature (or colour) of a star and its luminosity. Following this premise and an original idea by Stuart Lowe, we asked ourselves if american astronomer as a group have a "Main Career Sequence" in the space of Peer Reviewed papers and "absolute" Google index. Here we expand on Stuart's original idea examining several cuts in publication and Google parameter space with the help of proper ADS data
Quasar Candidates in the Hubble Deep Field1
The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study ... more The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study a wide range of questions in galaxy evolution and cosmology. Here we focus on the search for unresolved faint quasars and AGN in the crude combine images using a multicolor imaging analysis that has proven very successful in recent years. Quasar selection was
Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 2014
Pursuing ground breaking science in a highly cost-constrained environment presents new challenges... more Pursuing ground breaking science in a highly cost-constrained environment presents new challenges to the development of future space astrophysics missions. Within the conventional cost models for large observatories, executing a flagship "mission after next" appears to be unstainable. To achieve our nation's science ambitions requires a new paradigm of system design, development and manufacture. This paper explores the nature of the current paradigm and proposes a series of steps to guide the entire community to a sustainable future.
The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study ... more The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study a wide range of questions in galaxy evolution and cosmology. Here we focus on the search for unresolved faint quasars and AGN in the crude combine images using a multicolor imaging analysis that has proven very successful in recent years. Quasar selection was carried out both in multicolor space and in "profile space". The latter is the multi-parameter space formed by the radial profiles of the objects in the different images. By combining the dither frames available for each filter, we were able to obtain well sampled radial profiles of the objects and measure their deviation from that of a stellar source. This procedure efficiently helps to overcome the problems caused by the WPFC2 undersampling. Furthermore, to identify areas of multicolor space where quasars might be expected, we generated synthetic quasar spectra in the range 1.0 < z < 5.5 including effects of intrinsic emission lines and absorption by Lyα forest and Lyman-limit systems, and computed expected quasar colors. We also developed routines to determine the completeness of our data to point sources in the observed filters. The data are 90% complete at 26.2 m , 28.0 m , 27.8 m , 26.8 m in the F300W, F450W, F606W and F814W filters respectively. We find 41 compact objects in the HDF: 1 pointlike object with colors consistent with quasars but 1 Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. 2 Currently at the NAPL, Keble Road, Oxford (UK), OX1 3RH-2inconsistent with that of ordinary stars, 7 pointlike objects with colors consistent with quasars or stars; 18 stars; and 15 slightly resolved objects, 12 of which have colors consistent with quasars or stars. The latter objects could be resolved active galactic nuclei or regions of intense star formation. We estimate the upper limit of unresolved and slightly resolved quasars/AGNs with V 606 < 27.0 and z < 3.5 to be 20 objects (16,200 per deg 2). We independently recovered a resolved, star-forming galaxy with a spectroscopically confirmed redshift of 3.368 and 5 spectroscopically confirmed stars. Both provide confirmation for the validity of our color and morphological modeling. We make a detailed comparison with previous studies of the HDF. We find good agreement among different authors on the number of stars in the HDF and the lack of quasar candidates with z > 3.5. We find more quasar candidates than previous work because of our more extensive modeling and use of the color information. Spectroscopic observations of the candidates are needed to determine which, if any, are quasars or AGNS.
In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has ta... more In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has taken major steps in making MAST's holdings available using VO-defined protocols and standards, and in implementing VO-based tools. For example, MAST has implemented the Simple Cone Search protocol, and all MAST mission searches may be returned in the VOTable format, allowing other archives to use
Software and Cyberinfrastructure for Astronomy, 2010
The challenges facing the developers of user interfaces for astronomy applications has never been... more The challenges facing the developers of user interfaces for astronomy applications has never been greater. Astronomers and engineers often use well-designed commercial and web applications outside their work environment and have come to expect a similar user experience with applications developed for their work tasks. The connectivity provided by the Internet and the ability to work from anywhere can improve
The Astrophysical Journal, 2009
In this second of a series of papers on spatially resolved star formation, we investigate the imp... more In this second of a series of papers on spatially resolved star formation, we investigate the impact of the density-morphology relation of galaxies on the spatial variation of star formation (SF) and its dependence on environment. We find that while a density-morphology relation is present for the sample, it cannot solely explain the observed suppression of SF in galaxies in high-density environments. We also find that early-type and late-type galaxies exhibit distinct radial star formation rate (SFR) distributions, with early-types having a SFR distribution that extends further relative to the galaxy scale length, compared to late-types at all densities. We find that a suppression of SF in the highest density environments is found in the highest star forming galaxies for both galaxy types. This suppression occurs in the innermost regions in late-types (r ≤ 0.125 Petrosian radii), and further out in radius in early-types (0.125 < r ≤ 0.25 Petrosian radii). When the full sample is considered no clear suppression of SF is detected, indicating that the environmental trends are driven only by the highest SF galaxies. We demonstrate that the density-morphology relation alone cannot account for the suppression of SF in the highest density environments. This points to an environmentally-governed evolutionary mechanism that affects the SF in the innermost regions in both early and late-type galaxies. We suggest that this is a natural consequence of the "downsizing" of SF in galaxies.
The Astronomical Journal, 2003
We analyze the photometric information contained in individual pixels of galaxies in the Hubble D... more We analyze the photometric information contained in individual pixels of galaxies in the Hubble Deep Field North (HDFN) using a new technique, pixelz, that combines predictions of evolutionary synthesis models with photometric redshift template fitting. Each spectral energy distribution template is a result of modeling of the detailed physical processes affecting gas properties and star formation efficiency. The criteria chosen to generate the SED templates is that of sampling a wide range of physical characteristics such as age, star formation rate, obscuration and metallicity. A key feature of our method is the sophisticated use of error analysis to generate error maps that define the reliability of the template fitting on pixel scales and allow for the separation of the interplay among dust, metallicity and star formation histories. This technique offers a number of advantages over traditional integrated color studies. As a first application, we derive the star formation and metallicity histories of galaxies in the HDFN. Our results show that the comoving density of star formation rate, determined from the UV luminosity density of sources in the HDFN, increases monotonically with redshift out to at least redshift of 5. This behavior can plausibly be explained by a smooth increase of the UV luminosity density with redshift coupled with an increase in the number of star forming regions as a function of redshift. We also find that the information contained in individual pixels in a galaxy can be linked to its morphological history. Finally, we derive the metal enrichment rate history of the universe and find it in good agreement with predictions based on the evolving HI content of Lyman-α QSO absorption line systems.
The GALEX public archive at MAST
Astrophysics and Space Science, 2011
The Galaxy Evolution Explorer (GALEX) was successfully launched on April 28, 2003. Over the last ... more The Galaxy Evolution Explorer (GALEX) was successfully launched on April 28, 2003. Over the last 7 years, the GALEX mission has expanded our understanding of the process of star formation and galaxy evolution. GALEX data, consisting of far-UV (1344-1786A) and near-UV (1771-2831A) imaging over most of the sky, and grism spectroscopy, are available to the entire astronomical community and to
Astrophysics and Space Science, 2011
We describe the content and properties of UV source catalogs from GALEX's All-Sky Imaging Survey ... more We describe the content and properties of UV source catalogs from GALEX's All-Sky Imaging Survey (AIS, 5σ depth ≈19.9(FUV)/20.8(NUV) mag, in the AB system) and Medium-depth Imaging Survey (MIS, 5σ depth ≈22.6(FUV)/22.7(NUV) mag), constructed by Bianchi L., et al.: Mon. Not. R. Astron. Soc. (2010, in press). The catalogs contain 65.3/12.6 million (AIS/MIS) unique UV sources with photometric error in NUV less than 0.5 mag, over 21 435(AIS)/1579(MIS) square degrees. Matched optical data from GSC-II provide additional B, R, I photometry for the brightest sources, and SDSS provides u g r i z photometry over 7325(AIS)/1103(MIS) square degrees overlap areas. We discuss statistical properties that are relevant for understanding sample selection biases and completeness, in potential science applications of these catalogs. The FUV (1344-1786 Å) and NUV (1771-2831 Å) photometry uniquely enable selection of the hottest stellar objects, in particular hot white dwarfs (WD), which are elusive at optical wavelengths because of their hot temperatures and faint luminosities. From the GALEX-SDSS matched sources we
The Astrophysical Journal Supplement Series, 2007
We use the Galaxy Evolution Explorer (GALEX) Medium and All-Sky Imaging Survey (MIS and AIS) data... more We use the Galaxy Evolution Explorer (GALEX) Medium and All-Sky Imaging Survey (MIS and AIS) data from the first public data release (GR1), matched to the Sloan Digital Sky Survey (SDSS) DR3 catalog, to perform source classification. The GALEX surveys provide photometry in far-and near-UV bands and the SDSS in five optical bands (u, g, r, i, z). The GR1/ DR3 overlapping areas are 363 (86) deg 2 for the GALEX AIS (MIS), for sources within the 0.5 central area of the GALEX fields. Our sample covers mostly jbj > 30 Galactic latitudes. We present statistical properties of the GALEX-SDSS matched sources catalog, containing >2 ; 10 6 objects detected in at least one UV band. We classify the matched sources by comparing the seven-band photometry to model colors constructed for different classes of astrophysical objects.
In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has ta... more In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has taken major steps in making MAST's holdings available using VO-defined protocols and standards, and in implementing VO-based tools. For example, MAST has implemented the Simple Cone Search protocol, and all MAST mission searches may be returned in the VOTable format, allowing other archives to use MAST data for their VO applications. We have made many of our popular High Level Science Products available through Simple Image Access Protocol (SIAP), and are implementing the VO Simple Spectral Access Protocol (SSAP). The cross correlation of VizieR catalogs with MAST missions is now possible, and illustrates the integration of VO services into MAST. The user can easily display the results from searches within MAST using the plotting tool VOPlot. MAST also participates in the NVO registry service. Thus, the user can harvest MAST holdings simultaneously with data from many other surveys and missions through the VO DataScope Data Inventory Service.
A Search for Quasars at 5< z< 6 from a Large-Area BTC Multicolor Survey: Spectroscopy of Candidates over 20 Square Degrees
We propose to obtain identification spectra of high redshift quasar candidates selected from 20 d... more We propose to obtain identification spectra of high redshift quasar candidates selected from 20 deg^2 of multicolor imaging taken with the BTC at the CTIO 4m telescope in November 1997 and November 1998. The primary targets are candidates for quasars at 5 < z < 6 and I < 22 chosen from VIZ imaging data. This allows for quasar selection to M_B < -24, providing a unique data set from which to calculate reliable quasar space densities and differentiate between different proposed forms of evolution in the quasar luminosity function at early epochs.
Interpreting the properties of galaxies
Galaxies exhibit a wide range of physical properties (eg, luminosities, colors, velocity widths, ... more Galaxies exhibit a wide range of physical properties (eg, luminosities, colors, velocity widths, star formation, gas and stellar content) and the evolutionary processes responsible for these properties are numerous and complex. Understanding which processes shape the ...
A User Interface Proof of Concept: GoogleEarth Applied to Astronomical Data
ABSTRACT By combining satellite imagery, maps, community supported data, and a powerful search te... more ABSTRACT By combining satellite imagery, maps, community supported data, and a powerful search technology, GoogleEarth allows anyone to explore, search and discover features on our planet. We want exploit this technology to provide similar access to astronomical imagery, data and related information.We will illustrate a proof of concept astronomical interface that invokes protocols and formats currently employed for Earth data by GoogleEarth. Our experiment demonstrates how community supplied and hosted data such as that provided by the National Virtual Observatory, can be revealed on top of the GoogleEarth application.
Visualizing Large Astronomical Data Holdings
ABSTRACT Scientific visualization involves the presentation of interactive or animated digital im... more ABSTRACT Scientific visualization involves the presentation of interactive or animated digital images for interpretation of potentially huge quantities of observed or simulated data. Astronomy Visualization has been a tool used to convey astrophysical concepts and the data obtained to probe the cosmos. With the emergence of large astrophysical data archives, improvements in computational power and new technologies for the desktop, visualization of astronomical data is being considered as a new tool for exploration of data archives with a goal to enhance education and public understanding of science. We will present results of some exploratory work in the use of visualization technologies from the perspective of education and outreach. These tools are also being developed to facilitate scientists' use of such large data repositories as well.
GALEX-SDSS Crossmatch In The Database
ABSTRACT
Astronomical Visualization for Education
ABSTRACT
Angular Clustering and the Role of Photometric Redshifts
With the new generation of deep, space-based imaging surveys, such as those proposed for the SNAP... more With the new generation of deep, space-based imaging surveys, such as those proposed for the SNAP satellite, we will have an unprecedented opportunity to characterize the evolution of the clustering properties of galaxies across a wide range of look-back times. We consider ...
Everybody Has a Sky
Many astronomers and amateurs have noted that upon discovery of Google Earth, after its release i... more Many astronomers and amateurs have noted that upon discovery of Google Earth, after its release in mid-2005, they thought it would be a great interface for astronomical data. We came to the Sky project along separate trajectories, but by January 2006 we had joined forces and engaged the GoogleEarth team in Mountain View, CA. After an initial high energy meeting with Google, in 2006, we began experiments using the GoogleEarth technology and protocols, specifically Keyhole Markup Language (KML), and designed a mechanism for placing HST press release images and ancillary information into the Google Earth interface. We will briefly describe our primary role in providing HST Press Release images and supplementary information on the images for the Sky interface. We also have explored catalog services from custom analysis provided through the new Hubble Legacy Archive. We also will mention our plans for interaction with the Virtual Observatory. We also have worked with colleagues at the Un...
The Astronomer's HR diagram
Most people who've taken an astronomy course are familiar with the Hertzsprung-Russell diagra... more Most people who've taken an astronomy course are familiar with the Hertzsprung-Russell diagram. It was developed to show the relationships between the temperature (or colour) of a star and its luminosity. Following this premise and an original idea by Stuart Lowe, we asked ourselves if american astronomer as a group have a "Main Career Sequence" in the space of Peer Reviewed papers and "absolute" Google index. Here we expand on Stuart's original idea examining several cuts in publication and Google parameter space with the help of proper ADS data
Quasar Candidates in the Hubble Deep Field1
The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study ... more The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study a wide range of questions in galaxy evolution and cosmology. Here we focus on the search for unresolved faint quasars and AGN in the crude combine images using a multicolor imaging analysis that has proven very successful in recent years. Quasar selection was
Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 2014
Pursuing ground breaking science in a highly cost-constrained environment presents new challenges... more Pursuing ground breaking science in a highly cost-constrained environment presents new challenges to the development of future space astrophysics missions. Within the conventional cost models for large observatories, executing a flagship "mission after next" appears to be unstainable. To achieve our nation's science ambitions requires a new paradigm of system design, development and manufacture. This paper explores the nature of the current paradigm and proposes a series of steps to guide the entire community to a sustainable future.
The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study ... more The Hubble Deep Field gives us an unprecedented view of our universe and an opportunity to study a wide range of questions in galaxy evolution and cosmology. Here we focus on the search for unresolved faint quasars and AGN in the crude combine images using a multicolor imaging analysis that has proven very successful in recent years. Quasar selection was carried out both in multicolor space and in "profile space". The latter is the multi-parameter space formed by the radial profiles of the objects in the different images. By combining the dither frames available for each filter, we were able to obtain well sampled radial profiles of the objects and measure their deviation from that of a stellar source. This procedure efficiently helps to overcome the problems caused by the WPFC2 undersampling. Furthermore, to identify areas of multicolor space where quasars might be expected, we generated synthetic quasar spectra in the range 1.0 < z < 5.5 including effects of intrinsic emission lines and absorption by Lyα forest and Lyman-limit systems, and computed expected quasar colors. We also developed routines to determine the completeness of our data to point sources in the observed filters. The data are 90% complete at 26.2 m , 28.0 m , 27.8 m , 26.8 m in the F300W, F450W, F606W and F814W filters respectively. We find 41 compact objects in the HDF: 1 pointlike object with colors consistent with quasars but 1 Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. 2 Currently at the NAPL, Keble Road, Oxford (UK), OX1 3RH-2inconsistent with that of ordinary stars, 7 pointlike objects with colors consistent with quasars or stars; 18 stars; and 15 slightly resolved objects, 12 of which have colors consistent with quasars or stars. The latter objects could be resolved active galactic nuclei or regions of intense star formation. We estimate the upper limit of unresolved and slightly resolved quasars/AGNs with V 606 < 27.0 and z < 3.5 to be 20 objects (16,200 per deg 2). We independently recovered a resolved, star-forming galaxy with a spectroscopically confirmed redshift of 3.368 and 5 spectroscopically confirmed stars. Both provide confirmation for the validity of our color and morphological modeling. We make a detailed comparison with previous studies of the HDF. We find good agreement among different authors on the number of stars in the HDF and the lack of quasar candidates with z > 3.5. We find more quasar candidates than previous work because of our more extensive modeling and use of the color information. Spectroscopic observations of the candidates are needed to determine which, if any, are quasars or AGNS.
In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has ta... more In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has taken major steps in making MAST's holdings available using VO-defined protocols and standards, and in implementing VO-based tools. For example, MAST has implemented the Simple Cone Search protocol, and all MAST mission searches may be returned in the VOTable format, allowing other archives to use
Software and Cyberinfrastructure for Astronomy, 2010
The challenges facing the developers of user interfaces for astronomy applications has never been... more The challenges facing the developers of user interfaces for astronomy applications has never been greater. Astronomers and engineers often use well-designed commercial and web applications outside their work environment and have come to expect a similar user experience with applications developed for their work tasks. The connectivity provided by the Internet and the ability to work from anywhere can improve
The Astrophysical Journal, 2009
In this second of a series of papers on spatially resolved star formation, we investigate the imp... more In this second of a series of papers on spatially resolved star formation, we investigate the impact of the density-morphology relation of galaxies on the spatial variation of star formation (SF) and its dependence on environment. We find that while a density-morphology relation is present for the sample, it cannot solely explain the observed suppression of SF in galaxies in high-density environments. We also find that early-type and late-type galaxies exhibit distinct radial star formation rate (SFR) distributions, with early-types having a SFR distribution that extends further relative to the galaxy scale length, compared to late-types at all densities. We find that a suppression of SF in the highest density environments is found in the highest star forming galaxies for both galaxy types. This suppression occurs in the innermost regions in late-types (r ≤ 0.125 Petrosian radii), and further out in radius in early-types (0.125 < r ≤ 0.25 Petrosian radii). When the full sample is considered no clear suppression of SF is detected, indicating that the environmental trends are driven only by the highest SF galaxies. We demonstrate that the density-morphology relation alone cannot account for the suppression of SF in the highest density environments. This points to an environmentally-governed evolutionary mechanism that affects the SF in the innermost regions in both early and late-type galaxies. We suggest that this is a natural consequence of the "downsizing" of SF in galaxies.
The Astronomical Journal, 2003
We analyze the photometric information contained in individual pixels of galaxies in the Hubble D... more We analyze the photometric information contained in individual pixels of galaxies in the Hubble Deep Field North (HDFN) using a new technique, pixelz, that combines predictions of evolutionary synthesis models with photometric redshift template fitting. Each spectral energy distribution template is a result of modeling of the detailed physical processes affecting gas properties and star formation efficiency. The criteria chosen to generate the SED templates is that of sampling a wide range of physical characteristics such as age, star formation rate, obscuration and metallicity. A key feature of our method is the sophisticated use of error analysis to generate error maps that define the reliability of the template fitting on pixel scales and allow for the separation of the interplay among dust, metallicity and star formation histories. This technique offers a number of advantages over traditional integrated color studies. As a first application, we derive the star formation and metallicity histories of galaxies in the HDFN. Our results show that the comoving density of star formation rate, determined from the UV luminosity density of sources in the HDFN, increases monotonically with redshift out to at least redshift of 5. This behavior can plausibly be explained by a smooth increase of the UV luminosity density with redshift coupled with an increase in the number of star forming regions as a function of redshift. We also find that the information contained in individual pixels in a galaxy can be linked to its morphological history. Finally, we derive the metal enrichment rate history of the universe and find it in good agreement with predictions based on the evolving HI content of Lyman-α QSO absorption line systems.
The GALEX public archive at MAST
Astrophysics and Space Science, 2011
The Galaxy Evolution Explorer (GALEX) was successfully launched on April 28, 2003. Over the last ... more The Galaxy Evolution Explorer (GALEX) was successfully launched on April 28, 2003. Over the last 7 years, the GALEX mission has expanded our understanding of the process of star formation and galaxy evolution. GALEX data, consisting of far-UV (1344-1786A) and near-UV (1771-2831A) imaging over most of the sky, and grism spectroscopy, are available to the entire astronomical community and to
Astrophysics and Space Science, 2011
We describe the content and properties of UV source catalogs from GALEX's All-Sky Imaging Survey ... more We describe the content and properties of UV source catalogs from GALEX's All-Sky Imaging Survey (AIS, 5σ depth ≈19.9(FUV)/20.8(NUV) mag, in the AB system) and Medium-depth Imaging Survey (MIS, 5σ depth ≈22.6(FUV)/22.7(NUV) mag), constructed by Bianchi L., et al.: Mon. Not. R. Astron. Soc. (2010, in press). The catalogs contain 65.3/12.6 million (AIS/MIS) unique UV sources with photometric error in NUV less than 0.5 mag, over 21 435(AIS)/1579(MIS) square degrees. Matched optical data from GSC-II provide additional B, R, I photometry for the brightest sources, and SDSS provides u g r i z photometry over 7325(AIS)/1103(MIS) square degrees overlap areas. We discuss statistical properties that are relevant for understanding sample selection biases and completeness, in potential science applications of these catalogs. The FUV (1344-1786 Å) and NUV (1771-2831 Å) photometry uniquely enable selection of the hottest stellar objects, in particular hot white dwarfs (WD), which are elusive at optical wavelengths because of their hot temperatures and faint luminosities. From the GALEX-SDSS matched sources we
The Astrophysical Journal Supplement Series, 2007
We use the Galaxy Evolution Explorer (GALEX) Medium and All-Sky Imaging Survey (MIS and AIS) data... more We use the Galaxy Evolution Explorer (GALEX) Medium and All-Sky Imaging Survey (MIS and AIS) data from the first public data release (GR1), matched to the Sloan Digital Sky Survey (SDSS) DR3 catalog, to perform source classification. The GALEX surveys provide photometry in far-and near-UV bands and the SDSS in five optical bands (u, g, r, i, z). The GR1/ DR3 overlapping areas are 363 (86) deg 2 for the GALEX AIS (MIS), for sources within the 0.5 central area of the GALEX fields. Our sample covers mostly jbj > 30 Galactic latitudes. We present statistical properties of the GALEX-SDSS matched sources catalog, containing >2 ; 10 6 objects detected in at least one UV band. We classify the matched sources by comparing the seven-band photometry to model colors constructed for different classes of astrophysical objects.
In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has ta... more In the past year, the Multimission Archive at the Space Telescope Science Institute (MAST) has taken major steps in making MAST's holdings available using VO-defined protocols and standards, and in implementing VO-based tools. For example, MAST has implemented the Simple Cone Search protocol, and all MAST mission searches may be returned in the VOTable format, allowing other archives to use MAST data for their VO applications. We have made many of our popular High Level Science Products available through Simple Image Access Protocol (SIAP), and are implementing the VO Simple Spectral Access Protocol (SSAP). The cross correlation of VizieR catalogs with MAST missions is now possible, and illustrates the integration of VO services into MAST. The user can easily display the results from searches within MAST using the plotting tool VOPlot. MAST also participates in the NVO registry service. Thus, the user can harvest MAST holdings simultaneously with data from many other surveys and missions through the VO DataScope Data Inventory Service.
A Search for Quasars at 5< z< 6 from a Large-Area BTC Multicolor Survey: Spectroscopy of Candidates over 20 Square Degrees
We propose to obtain identification spectra of high redshift quasar candidates selected from 20 d... more We propose to obtain identification spectra of high redshift quasar candidates selected from 20 deg^2 of multicolor imaging taken with the BTC at the CTIO 4m telescope in November 1997 and November 1998. The primary targets are candidates for quasars at 5 < z < 6 and I < 22 chosen from VIZ imaging data. This allows for quasar selection to M_B < -24, providing a unique data set from which to calculate reliable quasar space densities and differentiate between different proposed forms of evolution in the quasar luminosity function at early epochs.
Interpreting the properties of galaxies
Galaxies exhibit a wide range of physical properties (eg, luminosities, colors, velocity widths, ... more Galaxies exhibit a wide range of physical properties (eg, luminosities, colors, velocity widths, star formation, gas and stellar content) and the evolutionary processes responsible for these properties are numerous and complex. Understanding which processes shape the ...
A User Interface Proof of Concept: GoogleEarth Applied to Astronomical Data
ABSTRACT By combining satellite imagery, maps, community supported data, and a powerful search te... more ABSTRACT By combining satellite imagery, maps, community supported data, and a powerful search technology, GoogleEarth allows anyone to explore, search and discover features on our planet. We want exploit this technology to provide similar access to astronomical imagery, data and related information.We will illustrate a proof of concept astronomical interface that invokes protocols and formats currently employed for Earth data by GoogleEarth. Our experiment demonstrates how community supplied and hosted data such as that provided by the National Virtual Observatory, can be revealed on top of the GoogleEarth application.
Visualizing Large Astronomical Data Holdings
ABSTRACT Scientific visualization involves the presentation of interactive or animated digital im... more ABSTRACT Scientific visualization involves the presentation of interactive or animated digital images for interpretation of potentially huge quantities of observed or simulated data. Astronomy Visualization has been a tool used to convey astrophysical concepts and the data obtained to probe the cosmos. With the emergence of large astrophysical data archives, improvements in computational power and new technologies for the desktop, visualization of astronomical data is being considered as a new tool for exploration of data archives with a goal to enhance education and public understanding of science. We will present results of some exploratory work in the use of visualization technologies from the perspective of education and outreach. These tools are also being developed to facilitate scientists' use of such large data repositories as well.