Ana Laura O'Mill | Famaf (original) (raw)
Papers by Ana Laura O'Mill
VizieR Online Data Catalog, Nov 1, 2012
We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sk... more We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sky Survey Seven Data Release (SDSS-DR7), available on the World Wide Web. The photometric redshifts were estimated with an artificial neural network using five ugriz bands, concentration indices and Petrosian radii in the g and r bands. We have explored our redshift estimates with different training set concluding that the best choice to improve redshift accuracy comprises the Main Galaxies Sample (MGS), the Luminous Red Galaxies, and galaxies of active galactic nuclei covering the redshift range 0<z<0.3. For the MGS, the photometric redshift estimates agree with the spectroscopic values within rms=0.0227. The derived distribution of photometric redshifts in the range 0<zphot<0.6 agrees well with the model predictions. k-corrections were derived by calibration of the k-correct-v4.2 code results for the MGS with the reference frame (z=0.1) (g-r) colours. We adopt a linear depen...
Monthly Notices of the Royal …, 2008
We use photometric redshifts to analyse the effect of local environment on galaxy colours at reds... more We use photometric redshifts to analyse the effect of local environment on galaxy colours at redshifts z≲ 0.63 in the Sloan Digital Sky Survey (SDSS) data release 6 (DR6). We construct mock SDSS-DR6 catalogues using semi-analytic galaxies to study possible systematic ...
We use the photometric redshifts technique to estimate redshifts in clusters for galaxies and fie... more We use the photometric redshifts technique to estimate redshifts in clusters for galaxies and field in the Sloan Digital Sky Survey (SDSS) without spectroscopic determinations. We apply the method of background discont modified to determine luminosity functions of galaxies in clusters beyond the spectroscopic limit of the SDSS. Preliminary results show that the use of photometric redshift and a cluster
The luminosity function of galaxies in clusters is derived assigning galaxies to clusters using t... more The luminosity function of galaxies in clusters is derived assigning galaxies to clusters using the photometric redshift technique. The present study addresses the universality of the faint galaxy population in clusters. An improved version of the decontamination method is presented. Our results indicate that the LF of galaxies in clusters follows a Schechter function with a flat faint end.
Monthly Notices of the Royal Astronomical Society, 2015
We study galaxy pair samples selected from the Sloan Digital Sky Survey (SDSS-DR7) and we perform... more We study galaxy pair samples selected from the Sloan Digital Sky Survey (SDSS-DR7) and we perform an analysis of minor and major mergers with the aim of investigating the dependence of galaxy properties on interactions. We build a galaxy pair catalog requiring r p < 25 kpc h-1 and V < 350 km s-1 within redshift z < 0.1. By visual inspection of SDSS images we removed false identifications and we classify the interactions into three cat- egories: pairs undergoing merging, M; pairs with evident tidal features, T ; and non disturbed, N. We also divide the pair sample into minor and major interactions according to the luminosity ratio of the galaxy members. We conclude that the characteristics of the interactions and the ratio of lumi- nosity galaxy pair members involved in a merger are important parameters in setting galaxy properties.
Using data from the last survey of Sloan Digital Sky Survey (SDSS-DR7), we obtained a sample of i... more Using data from the last survey of Sloan Digital Sky Survey (SDSS-DR7), we obtained a sample of interacting galaxy pairs, statistically reliable and we classified the type of interaction, for the purpose of analyzing the char- acteristics of these systems. Studies were developed in different density environments to understand how these processes affect both the field iso- lated galaxies and those found in dense regions in clusters. FULL TEXT IN SPANISH
We used photometric redshifts to analyse the environment of luminous red galaxies at redshift ran... more We used photometric redshifts to analyse the environment of luminous red galaxies at redshift range 0.25
In this work we have performed a visual inspection of aproximately 10000 pairs of galaxies. We ob... more In this work we have performed a visual inspection of aproximately 10000 pairs of galaxies. We obtained a sample free of systematic effects and we analized the evolution of their principal features. We found that aproxi- mately 20% of the pairs are in merging phase. FULL TEXT IN SPANISH
ABSTRACT We present preliminary results of the construction of a catalog of interacting triple ga... more ABSTRACT We present preliminary results of the construction of a catalog of interacting triple galaxy systems. For the identification we have analyzed both spectro- scopic and photometric data and applied restrictions on projected distance and radial velocity differences of member galaxies. FULL TEXT IN SPANISH
We present a new catalogue of galaxy triplets derived from the Sloan Digital Sky Survey Data Rele... more We present a new catalogue of galaxy triplets derived from the Sloan Digital Sky Survey Data Release 7. The identification of systems was performed considering galaxies brighter than M r = −20.5 and imposing constraints over the projected distances, radial velocity differences of neighbouring galaxies and isolation. To improve the identification of triplets we employed a data pixelization scheme, which allows to handle large amounts of data as in the SDSS photometric survey. Using spectroscopic and photometric data in the redshift range 0.01 z 0.40 we obtain 5901 triplet candidates. We have used a mock catalogue to analyse the completeness and contamination of our methods. The results show a high level of completeness (∼ 80%) and low contamination (∼ 5%). By using photometric and spectroscopic data we have also addressed the effects of fiber collisions in the spectroscopic sample. We have defined an isolation criterion considering the distance of the triplet brightest galaxy to closest neighbour cluster, to describe a global environment, as well as the galaxies within a fixed aperture, around the triplet brightest galaxy, to measure the local environment. The final catalogue comprises 1092 isolated triplets of galaxies in the redshift range 0.01 z 0.40. Our results show that photometric redshifts provide very useful information, allowing to complete the sample of nearby systems whose detection is affected by fiber collisions, as well as extending the detection of triplets to large distances, where spectroscopic redshifts are not available.
ABSTRACT In this work, we employed spectroscopic and photometric data extracted from SDSS DR7. (1... more ABSTRACT In this work, we employed spectroscopic and photometric data extracted from SDSS DR7. (1 data file).
We present new estimates for photometric redshift and k corrections for the seven realease of the... more We present new estimates for photometric redshift and k corrections for the seven realease of the SDSS (SDSS-DR7). Photometric redshifts were estimated using artificial neural networks, obtaining 0 < z_phot <= 0.6 with a rms = 0.0227. k corrections were obtained by double parametization with redshift and (g - r) reference-frame color. The results show that a simple linear relationship
The sample of radio sources was selected from the catalogue of Kimball & Ivezic (2008AJ....136..6... more The sample of radio sources was selected from the catalogue of Kimball & Ivezic (2008AJ....136..684K). The sample of optical galaxies in the fields of radio sources was selected using the Catalog Archive Server Jobs System (CASJOBS) interface of SDSS, which allows one to obtain catalogues with parameters from the SDSS Data Release 6 (DR6). (1 data file).
Monthly Notices of the Royal Astronomical Society, 2008
We use photometric redshifts to analyse the effect of local environment on galaxy colours at reds... more We use photometric redshifts to analyse the effect of local environment on galaxy colours at redshifts z 0.63 in the SDSS data release 6. We construct mock SDSS-DR6 catalogues using semi-analytic galaxies to study possible systematic effects on the characterisation of environment and colour statistics due to the uncertainty in the determination of redshifts. We use the projected galaxy density derived from the distance to the nearest neighbours with a suitable radial velocity threshold to take into account the uncertainties in the photometric redshift estimates. Our findings indicate that the use of photometric redshifts greatly improves estimates of projected local galaxy density when galaxy spectra are not available. We find a tight relationship between spectroscopic and photometric derived densities, both in the SDSS-DR6 data (up to z = 0.3) and mock catalogues (up to z = 0.63).
Monthly Notices of the Royal Astronomical Society, 2011
We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sk... more We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sky Survey Seven Data Release (SDSS-DR7), available on the World Wide Web. The photometric redshifts were estimated with an artificial neural network using five ugriz bands, concentration indices and Petrosian radii in the g and r bands. We have explored our redshift estimates with different training set concluding that the best choice to improve redshift accuracy comprises the Main Galaxies Sample (MGS), the Luminous Red Galaxies, and galaxies of active galactic nuclei covering the redshift range 0 < z 0.3. For the MGS, the photometric redshift estimates agree with the spectroscopic values within rms = 0.0227. The derived distribution of photometric redshifts in the range 0 < z phot 0.6 agrees well with the model predictions. k-corrections were derived by calibration of the k-correct v4.2 code results for the MGS with the reference frame (z = 0.1) (g − r) colours. We adopt a linear dependence of k corrections on redshift and (g − r) colours that provide suitable distributions of luminosity and colours for galaxies up to redshift z phot = 0.6 comparable to the results in the literature. Thus, our k-correction estimate procedure is a powerful, low computational time algorithm capable of reproducing suitable results that can be used for testing galaxy properties at intermediate redshifts using the large SDSS database.
Monthly Notices of the Royal Astronomical Society, 2012
ABSTRACT We analyse a sample of 71 triplets of luminous galaxies derived from the work of O&#... more ABSTRACT We analyse a sample of 71 triplets of luminous galaxies derived from the work of O'Mill et al. (2012). We compare the properties of triplets and their members with those of control samples of compact groups, the ten brightest members of rich clusters, and galaxies in pairs. The triplets are restricted to have members with spectroscopic redshifts in the range 0.01<z<0.14 and Mr<-20.5. We analyse the stellar mass (SM) content, the star formation rates, the Dn(4000) parameter and colour index and also analyse different global properties of these systems as total star formation activity and global colours. We calculate the probability that the properties of galaxies in triplets are strongly correlated. We define the triplet compactness as a measure of the percentage of the system total area that is filled by the light of member galaxies. Our analysis suggest that triplet galaxy members behave similarly to compact group members and galaxies in rich clusters. We also find that systems comprising 3 blue, star-forming, young stellar population galaxies (blue triplets) are most probably real systems and not a chance configuration of interloping galaxies. The same holds for triplets composed by 3 red, non star-forming galaxies, showing the correlation of galaxy properties in these systems. From the analysis of the triplet as a whole, we conclude that, at a given total SM content, triplets show a total star formation activity and global colours similar to compact groups. However, blue triplets show a high total star formation activity with a lower SM content. From an analysis of the compactness parameter of the systems we find that light is even more concentrated in triplets than in compact groups. We propose that triplets composed by 3 luminous galaxies, should not be considered as an analogous of galaxy pairs with an extra member, but rather they are a natural extension of compact groups.
Monthly Notices of the …, Jan 1, 2010
Monthly Notices of the Royal Astronomical Society, 2006
We analyse u − r colour distributions for several samples of galaxies in groups drawn from the Fo... more We analyse u − r colour distributions for several samples of galaxies in groups drawn from the Fourth Data Release of the Sloan Digital Sky Survey. For all luminosity ranges and environments considered the colour distributions are well described by the sum of two Gaussian functions. We find that the fraction of galaxies in the red sequence is an increasing function of group virial mass. We also study the evolution of the galaxy colour distributions at low redshift, z ≤ 0.18 in the field and in groups for galaxies brighter than M r − 5 log(h) = −20, finding significant evidence of recent evolution in the population of galaxies in groups. The fraction of red galaxies monotonically increases with decreasing redshift, this effect implies a much stronger evolution of galaxies in groups than in the field.
VizieR Online Data Catalog, Nov 1, 2012
We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sk... more We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sky Survey Seven Data Release (SDSS-DR7), available on the World Wide Web. The photometric redshifts were estimated with an artificial neural network using five ugriz bands, concentration indices and Petrosian radii in the g and r bands. We have explored our redshift estimates with different training set concluding that the best choice to improve redshift accuracy comprises the Main Galaxies Sample (MGS), the Luminous Red Galaxies, and galaxies of active galactic nuclei covering the redshift range 0<z<0.3. For the MGS, the photometric redshift estimates agree with the spectroscopic values within rms=0.0227. The derived distribution of photometric redshifts in the range 0<zphot<0.6 agrees well with the model predictions. k-corrections were derived by calibration of the k-correct-v4.2 code results for the MGS with the reference frame (z=0.1) (g-r) colours. We adopt a linear depen...
Monthly Notices of the Royal …, 2008
We use photometric redshifts to analyse the effect of local environment on galaxy colours at reds... more We use photometric redshifts to analyse the effect of local environment on galaxy colours at redshifts z≲ 0.63 in the Sloan Digital Sky Survey (SDSS) data release 6 (DR6). We construct mock SDSS-DR6 catalogues using semi-analytic galaxies to study possible systematic ...
We use the photometric redshifts technique to estimate redshifts in clusters for galaxies and fie... more We use the photometric redshifts technique to estimate redshifts in clusters for galaxies and field in the Sloan Digital Sky Survey (SDSS) without spectroscopic determinations. We apply the method of background discont modified to determine luminosity functions of galaxies in clusters beyond the spectroscopic limit of the SDSS. Preliminary results show that the use of photometric redshift and a cluster
The luminosity function of galaxies in clusters is derived assigning galaxies to clusters using t... more The luminosity function of galaxies in clusters is derived assigning galaxies to clusters using the photometric redshift technique. The present study addresses the universality of the faint galaxy population in clusters. An improved version of the decontamination method is presented. Our results indicate that the LF of galaxies in clusters follows a Schechter function with a flat faint end.
Monthly Notices of the Royal Astronomical Society, 2015
We study galaxy pair samples selected from the Sloan Digital Sky Survey (SDSS-DR7) and we perform... more We study galaxy pair samples selected from the Sloan Digital Sky Survey (SDSS-DR7) and we perform an analysis of minor and major mergers with the aim of investigating the dependence of galaxy properties on interactions. We build a galaxy pair catalog requiring r p < 25 kpc h-1 and V < 350 km s-1 within redshift z < 0.1. By visual inspection of SDSS images we removed false identifications and we classify the interactions into three cat- egories: pairs undergoing merging, M; pairs with evident tidal features, T ; and non disturbed, N. We also divide the pair sample into minor and major interactions according to the luminosity ratio of the galaxy members. We conclude that the characteristics of the interactions and the ratio of lumi- nosity galaxy pair members involved in a merger are important parameters in setting galaxy properties.
Using data from the last survey of Sloan Digital Sky Survey (SDSS-DR7), we obtained a sample of i... more Using data from the last survey of Sloan Digital Sky Survey (SDSS-DR7), we obtained a sample of interacting galaxy pairs, statistically reliable and we classified the type of interaction, for the purpose of analyzing the char- acteristics of these systems. Studies were developed in different density environments to understand how these processes affect both the field iso- lated galaxies and those found in dense regions in clusters. FULL TEXT IN SPANISH
We used photometric redshifts to analyse the environment of luminous red galaxies at redshift ran... more We used photometric redshifts to analyse the environment of luminous red galaxies at redshift range 0.25
In this work we have performed a visual inspection of aproximately 10000 pairs of galaxies. We ob... more In this work we have performed a visual inspection of aproximately 10000 pairs of galaxies. We obtained a sample free of systematic effects and we analized the evolution of their principal features. We found that aproxi- mately 20% of the pairs are in merging phase. FULL TEXT IN SPANISH
ABSTRACT We present preliminary results of the construction of a catalog of interacting triple ga... more ABSTRACT We present preliminary results of the construction of a catalog of interacting triple galaxy systems. For the identification we have analyzed both spectro- scopic and photometric data and applied restrictions on projected distance and radial velocity differences of member galaxies. FULL TEXT IN SPANISH
We present a new catalogue of galaxy triplets derived from the Sloan Digital Sky Survey Data Rele... more We present a new catalogue of galaxy triplets derived from the Sloan Digital Sky Survey Data Release 7. The identification of systems was performed considering galaxies brighter than M r = −20.5 and imposing constraints over the projected distances, radial velocity differences of neighbouring galaxies and isolation. To improve the identification of triplets we employed a data pixelization scheme, which allows to handle large amounts of data as in the SDSS photometric survey. Using spectroscopic and photometric data in the redshift range 0.01 z 0.40 we obtain 5901 triplet candidates. We have used a mock catalogue to analyse the completeness and contamination of our methods. The results show a high level of completeness (∼ 80%) and low contamination (∼ 5%). By using photometric and spectroscopic data we have also addressed the effects of fiber collisions in the spectroscopic sample. We have defined an isolation criterion considering the distance of the triplet brightest galaxy to closest neighbour cluster, to describe a global environment, as well as the galaxies within a fixed aperture, around the triplet brightest galaxy, to measure the local environment. The final catalogue comprises 1092 isolated triplets of galaxies in the redshift range 0.01 z 0.40. Our results show that photometric redshifts provide very useful information, allowing to complete the sample of nearby systems whose detection is affected by fiber collisions, as well as extending the detection of triplets to large distances, where spectroscopic redshifts are not available.
ABSTRACT In this work, we employed spectroscopic and photometric data extracted from SDSS DR7. (1... more ABSTRACT In this work, we employed spectroscopic and photometric data extracted from SDSS DR7. (1 data file).
We present new estimates for photometric redshift and k corrections for the seven realease of the... more We present new estimates for photometric redshift and k corrections for the seven realease of the SDSS (SDSS-DR7). Photometric redshifts were estimated using artificial neural networks, obtaining 0 < z_phot <= 0.6 with a rms = 0.0227. k corrections were obtained by double parametization with redshift and (g - r) reference-frame color. The results show that a simple linear relationship
The sample of radio sources was selected from the catalogue of Kimball & Ivezic (2008AJ....136..6... more The sample of radio sources was selected from the catalogue of Kimball & Ivezic (2008AJ....136..684K). The sample of optical galaxies in the fields of radio sources was selected using the Catalog Archive Server Jobs System (CASJOBS) interface of SDSS, which allows one to obtain catalogues with parameters from the SDSS Data Release 6 (DR6). (1 data file).
Monthly Notices of the Royal Astronomical Society, 2008
We use photometric redshifts to analyse the effect of local environment on galaxy colours at reds... more We use photometric redshifts to analyse the effect of local environment on galaxy colours at redshifts z 0.63 in the SDSS data release 6. We construct mock SDSS-DR6 catalogues using semi-analytic galaxies to study possible systematic effects on the characterisation of environment and colour statistics due to the uncertainty in the determination of redshifts. We use the projected galaxy density derived from the distance to the nearest neighbours with a suitable radial velocity threshold to take into account the uncertainties in the photometric redshift estimates. Our findings indicate that the use of photometric redshifts greatly improves estimates of projected local galaxy density when galaxy spectra are not available. We find a tight relationship between spectroscopic and photometric derived densities, both in the SDSS-DR6 data (up to z = 0.3) and mock catalogues (up to z = 0.63).
Monthly Notices of the Royal Astronomical Society, 2011
We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sk... more We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sky Survey Seven Data Release (SDSS-DR7), available on the World Wide Web. The photometric redshifts were estimated with an artificial neural network using five ugriz bands, concentration indices and Petrosian radii in the g and r bands. We have explored our redshift estimates with different training set concluding that the best choice to improve redshift accuracy comprises the Main Galaxies Sample (MGS), the Luminous Red Galaxies, and galaxies of active galactic nuclei covering the redshift range 0 < z 0.3. For the MGS, the photometric redshift estimates agree with the spectroscopic values within rms = 0.0227. The derived distribution of photometric redshifts in the range 0 < z phot 0.6 agrees well with the model predictions. k-corrections were derived by calibration of the k-correct v4.2 code results for the MGS with the reference frame (z = 0.1) (g − r) colours. We adopt a linear dependence of k corrections on redshift and (g − r) colours that provide suitable distributions of luminosity and colours for galaxies up to redshift z phot = 0.6 comparable to the results in the literature. Thus, our k-correction estimate procedure is a powerful, low computational time algorithm capable of reproducing suitable results that can be used for testing galaxy properties at intermediate redshifts using the large SDSS database.
Monthly Notices of the Royal Astronomical Society, 2012
ABSTRACT We analyse a sample of 71 triplets of luminous galaxies derived from the work of O&#... more ABSTRACT We analyse a sample of 71 triplets of luminous galaxies derived from the work of O'Mill et al. (2012). We compare the properties of triplets and their members with those of control samples of compact groups, the ten brightest members of rich clusters, and galaxies in pairs. The triplets are restricted to have members with spectroscopic redshifts in the range 0.01<z<0.14 and Mr<-20.5. We analyse the stellar mass (SM) content, the star formation rates, the Dn(4000) parameter and colour index and also analyse different global properties of these systems as total star formation activity and global colours. We calculate the probability that the properties of galaxies in triplets are strongly correlated. We define the triplet compactness as a measure of the percentage of the system total area that is filled by the light of member galaxies. Our analysis suggest that triplet galaxy members behave similarly to compact group members and galaxies in rich clusters. We also find that systems comprising 3 blue, star-forming, young stellar population galaxies (blue triplets) are most probably real systems and not a chance configuration of interloping galaxies. The same holds for triplets composed by 3 red, non star-forming galaxies, showing the correlation of galaxy properties in these systems. From the analysis of the triplet as a whole, we conclude that, at a given total SM content, triplets show a total star formation activity and global colours similar to compact groups. However, blue triplets show a high total star formation activity with a lower SM content. From an analysis of the compactness parameter of the systems we find that light is even more concentrated in triplets than in compact groups. We propose that triplets composed by 3 luminous galaxies, should not be considered as an analogous of galaxy pairs with an extra member, but rather they are a natural extension of compact groups.
Monthly Notices of the …, Jan 1, 2010
Monthly Notices of the Royal Astronomical Society, 2006
We analyse u − r colour distributions for several samples of galaxies in groups drawn from the Fo... more We analyse u − r colour distributions for several samples of galaxies in groups drawn from the Fourth Data Release of the Sloan Digital Sky Survey. For all luminosity ranges and environments considered the colour distributions are well described by the sum of two Gaussian functions. We find that the fraction of galaxies in the red sequence is an increasing function of group virial mass. We also study the evolution of the galaxy colour distributions at low redshift, z ≤ 0.18 in the field and in groups for galaxies brighter than M r − 5 log(h) = −20, finding significant evidence of recent evolution in the population of galaxies in groups. The fraction of red galaxies monotonically increases with decreasing redshift, this effect implies a much stronger evolution of galaxies in groups than in the field.