The quasar in the Hubble Deep Field South (HDFS), J2233–606 (zem = 2.23) has been exhaustively ob... more The quasar in the Hubble Deep Field South (HDFS), J2233–606 (zem = 2.23) has been exhaustively observed by ground based telescopes and by the STIS spectrograph on board the Hubble Space Telescope (HST) at low, medium and high resolution in the spectral interval from 1120 ˚A to 10000 ˚A. The combined data give continuous coverage of the Lyman–α forest from redshift 0.9 to 2.24. This very large base–line represents a unique opportunity to study in detail the distribution of clouds associated with emitting structures in the field of the quasar and in nearby fields already observed as part of the HDFS campaign. Here we report the main properties obtained from the large spectroscopic dataset available for the Lyα clouds in the intermediate redshift range 1.20 − 2.20, where our present knowledge has been complicated by the difficulty in producing good data. The number density is shown to be higher than what is expected by extrapolating the results from both lower and higher redshifts: 63 ...
Symposium - International Astronomical Union, 2004
Due to their extremely small luminosity compared to the stars they orbit, planets outside our own... more Due to their extremely small luminosity compared to the stars they orbit, planets outside our own Solar System are extraordinarily difficult to detect directly in optical light. Careful photometric monitoring of distant stars, however, can reveal the presence of exoplanets via the microlensing or eclipsing effects they induce. The international PLANET collaboration is performing such monitoring using a cadre of semi-dedicated telescopes around the world. Their results constrain the number of gas giants orbiting 1–7 AU from the most typical stars in the Galaxy. Upgrades in the program are opening regions of “exoplanet discovery space” – toward smaller masses and larger orbital radii – that are inaccessible to the Doppler velocity technique.
An ecosystem disruptive bloom of red Noctiluca scintillans (hereafter Noctiluca) was observed in ... more An ecosystem disruptive bloom of red Noctiluca scintillans (hereafter Noctiluca) was observed in coastal waters of the north-western Bay of Bengal during April 2014. Based on the principle of phytoplankton group/species specific remote sensing reflectance (Rrs), a technique of detecting green Noctiluca and diatom was developed earlier using Rrs at 443, 488, and 531 nm of Moderate Imaging Spectroradiometer-Aqua (MODIS). This was appropriately modified to detect bloom of red Noctiluca in coastal waters of the Bay of Bengal. Additional Rrs data at longer wavelengths viz. 667 and 678 nm were included in the existing algorithm, and the spectral shapes were accounted to detect the bloom of red Noctiluca. The classification scheme discriminates red Noctiluca from the green form of the same species and diatom. Phytoplankton group/species products were generated using the modified approach and validated with the reported events of red and green Noctiluca blooms in the Indian coastal waters. ...
A comprehensive analysis on seasonal distribution of phytoplankton community structure and their ... more A comprehensive analysis on seasonal distribution of phytoplankton community structure and their interaction with environmental variables was carried out in two local water types (type 1 < 30 m isobath and Type 2 > 30 m isobath) at a coastal site in north-western Bay of Bengal. Phytoplankton community was represented by 211 taxa (146 marine, 37 fresh, 2 brackish, 20 marine-fresh, and 6 marine-brackish-fresh) belonging to seven major groups including 45 potential bloom forming and 22 potential toxin producing species. The seasonal variability depicted enrichment of phytoplankton during pre-monsoon in both water types. Total phytoplankton abundance pattern observed with inter-annual shift during monsoon and post-monsoon period at both water types. In both water types, diatom predominance was observed in terms of species richness and abundance comprising of centric (82 sp.) and pennate (58 sp.) forms. Pennate diatoms, Thalassiothrix longissima and Skeletonema costatum preponderat...
Maps of the dark cloud ESO 210-6A and the associated NIR source HH 46/47 were constructed using I... more Maps of the dark cloud ESO 210-6A and the associated NIR source HH 46/47 were constructed using IRAS data. The 60/100 micron color temperature distribution in the cloud shows that the temperature in the cloud ranges from 20 to 40 K, with the maximum temperature at the position of the NIR source. On the other hand, the 12/25 micron color temperature distribution shows temperatures ranging from 200 to 400 K, and exhibits a minimum at the position of the NIR source. Such an anticorrelation between 12/25 micron and 60/100 micron temperature distributions extends to all parts of the cloud. The dust mass and the FIR luminosity of the ESO 210-6A dark cloud, derived from the 60-micron and 100-micron fluxes, were found to be about 0.08 solar mass and 44 solar luminosities, respectively.
The present study focuses on understanding the long-term distribution of physico-chemical paramet... more The present study focuses on understanding the long-term distribution of physico-chemical parameters and their influence on the distribution of chlorophyll-a (chl-a) at a coastal site in the northwestern Bay of Bengal. Chl-a showed large variability (0.12 to 10.05 mg m(-3)) on a spatio-temporal scale during the study period. However, the distribution showed a similar pattern with marginal variability from March 2010 to February 2011 and March 2011 to February 2012. The vertical distribution of salinity, pH, total suspended matter (TSM) and chl-a showed systematic temporal variability. However, dissolved oxygen (DO) and nutrients (nitrite + nitrate, phosphate, silicate) did not show any significant spatio-temporal trend. Chl-a showed bimodal distribution on an annual scale, with the first peak appearing during the pre-monsoon period in March due to a seasonal phytoplankton bloom, whereas the second peak occurring during September as a result of nutrient loading from river influx due to monsoonal precipitation. Factor analysis revealed the association of low salinity and high nutrients with chl-a. This infers that the nutrients brought by the influx of river into the study area were fuelling the growth and abundance of phytoplankton. Cluster analysis resulted in two distinct clusters among all physico-chemical datasets, indicating the presence of two distinct areas separated by the 30 m isobath that were strongly influenced by physico-chemical characteristics associated with the seasonal monsoon.
The Probing Lensing Anomalies NETwork is an international collaboration that makes coordinated ob... more The Probing Lensing Anomalies NETwork is an international collaboration that makes coordinated observations of on-going graviational microlensing events from four sites in the southern hemisphere. One of our primary goals is to detect planets around other stars from their microlensing effect. During the 1998 bulge observing season we intensely monitored numerous microlensing events; one event was observed more than 500
... 1 m, Sutherland, South Africa). Dedicated observations of ongoing microlensing in the Galacti... more ... 1 m, Sutherland, South Africa). Dedicated observations of ongoing microlensing in the Galactic bulge will be made from April to September, with most of the observingdone in the V, I and H bands. Each site reduces the data ...
The quasar in the Hubble Deep Field South (HDFS), J2233–606 (zem = 2.23) has been exhaustively ob... more The quasar in the Hubble Deep Field South (HDFS), J2233–606 (zem = 2.23) has been exhaustively observed by ground based telescopes and by the STIS spectrograph on board the Hubble Space Telescope (HST) at low, medium and high resolution in the spectral interval from 1120 ˚A to 10000 ˚A. The combined data give continuous coverage of the Lyman–α forest from redshift 0.9 to 2.24. This very large base–line represents a unique opportunity to study in detail the distribution of clouds associated with emitting structures in the field of the quasar and in nearby fields already observed as part of the HDFS campaign. Here we report the main properties obtained from the large spectroscopic dataset available for the Lyα clouds in the intermediate redshift range 1.20 − 2.20, where our present knowledge has been complicated by the difficulty in producing good data. The number density is shown to be higher than what is expected by extrapolating the results from both lower and higher redshifts: 63 ...
Symposium - International Astronomical Union, 2004
Due to their extremely small luminosity compared to the stars they orbit, planets outside our own... more Due to their extremely small luminosity compared to the stars they orbit, planets outside our own Solar System are extraordinarily difficult to detect directly in optical light. Careful photometric monitoring of distant stars, however, can reveal the presence of exoplanets via the microlensing or eclipsing effects they induce. The international PLANET collaboration is performing such monitoring using a cadre of semi-dedicated telescopes around the world. Their results constrain the number of gas giants orbiting 1–7 AU from the most typical stars in the Galaxy. Upgrades in the program are opening regions of “exoplanet discovery space” – toward smaller masses and larger orbital radii – that are inaccessible to the Doppler velocity technique.
An ecosystem disruptive bloom of red Noctiluca scintillans (hereafter Noctiluca) was observed in ... more An ecosystem disruptive bloom of red Noctiluca scintillans (hereafter Noctiluca) was observed in coastal waters of the north-western Bay of Bengal during April 2014. Based on the principle of phytoplankton group/species specific remote sensing reflectance (Rrs), a technique of detecting green Noctiluca and diatom was developed earlier using Rrs at 443, 488, and 531 nm of Moderate Imaging Spectroradiometer-Aqua (MODIS). This was appropriately modified to detect bloom of red Noctiluca in coastal waters of the Bay of Bengal. Additional Rrs data at longer wavelengths viz. 667 and 678 nm were included in the existing algorithm, and the spectral shapes were accounted to detect the bloom of red Noctiluca. The classification scheme discriminates red Noctiluca from the green form of the same species and diatom. Phytoplankton group/species products were generated using the modified approach and validated with the reported events of red and green Noctiluca blooms in the Indian coastal waters. ...
A comprehensive analysis on seasonal distribution of phytoplankton community structure and their ... more A comprehensive analysis on seasonal distribution of phytoplankton community structure and their interaction with environmental variables was carried out in two local water types (type 1 < 30 m isobath and Type 2 > 30 m isobath) at a coastal site in north-western Bay of Bengal. Phytoplankton community was represented by 211 taxa (146 marine, 37 fresh, 2 brackish, 20 marine-fresh, and 6 marine-brackish-fresh) belonging to seven major groups including 45 potential bloom forming and 22 potential toxin producing species. The seasonal variability depicted enrichment of phytoplankton during pre-monsoon in both water types. Total phytoplankton abundance pattern observed with inter-annual shift during monsoon and post-monsoon period at both water types. In both water types, diatom predominance was observed in terms of species richness and abundance comprising of centric (82 sp.) and pennate (58 sp.) forms. Pennate diatoms, Thalassiothrix longissima and Skeletonema costatum preponderat...
Maps of the dark cloud ESO 210-6A and the associated NIR source HH 46/47 were constructed using I... more Maps of the dark cloud ESO 210-6A and the associated NIR source HH 46/47 were constructed using IRAS data. The 60/100 micron color temperature distribution in the cloud shows that the temperature in the cloud ranges from 20 to 40 K, with the maximum temperature at the position of the NIR source. On the other hand, the 12/25 micron color temperature distribution shows temperatures ranging from 200 to 400 K, and exhibits a minimum at the position of the NIR source. Such an anticorrelation between 12/25 micron and 60/100 micron temperature distributions extends to all parts of the cloud. The dust mass and the FIR luminosity of the ESO 210-6A dark cloud, derived from the 60-micron and 100-micron fluxes, were found to be about 0.08 solar mass and 44 solar luminosities, respectively.
The present study focuses on understanding the long-term distribution of physico-chemical paramet... more The present study focuses on understanding the long-term distribution of physico-chemical parameters and their influence on the distribution of chlorophyll-a (chl-a) at a coastal site in the northwestern Bay of Bengal. Chl-a showed large variability (0.12 to 10.05 mg m(-3)) on a spatio-temporal scale during the study period. However, the distribution showed a similar pattern with marginal variability from March 2010 to February 2011 and March 2011 to February 2012. The vertical distribution of salinity, pH, total suspended matter (TSM) and chl-a showed systematic temporal variability. However, dissolved oxygen (DO) and nutrients (nitrite + nitrate, phosphate, silicate) did not show any significant spatio-temporal trend. Chl-a showed bimodal distribution on an annual scale, with the first peak appearing during the pre-monsoon period in March due to a seasonal phytoplankton bloom, whereas the second peak occurring during September as a result of nutrient loading from river influx due to monsoonal precipitation. Factor analysis revealed the association of low salinity and high nutrients with chl-a. This infers that the nutrients brought by the influx of river into the study area were fuelling the growth and abundance of phytoplankton. Cluster analysis resulted in two distinct clusters among all physico-chemical datasets, indicating the presence of two distinct areas separated by the 30 m isobath that were strongly influenced by physico-chemical characteristics associated with the seasonal monsoon.
The Probing Lensing Anomalies NETwork is an international collaboration that makes coordinated ob... more The Probing Lensing Anomalies NETwork is an international collaboration that makes coordinated observations of on-going graviational microlensing events from four sites in the southern hemisphere. One of our primary goals is to detect planets around other stars from their microlensing effect. During the 1998 bulge observing season we intensely monitored numerous microlensing events; one event was observed more than 500
... 1 m, Sutherland, South Africa). Dedicated observations of ongoing microlensing in the Galacti... more ... 1 m, Sutherland, South Africa). Dedicated observations of ongoing microlensing in the Galactic bulge will be made from April to September, with most of the observingdone in the V, I and H bands. Each site reduces the data ...
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