Brown dwarfs and very low mass stars in the Praesepe open cluster: a dynamically unevolved mass function?

[Abridged] In this paper, we present the results of a photometric survey to identify low mass and brown dwarf members of the old open cluster Praesepe (age of 590[+150][-120]Myr and distance of 190[+6.0][-5.8]pc) and use this to infer its mass function which we compare with that of other clusters. We have performed an optical (Ic-band) and near-infrared (J and Ks-band) photometric survey of Praesepe with a spatial coverage of 3.1deg^2. With 5sigma detection limits of Ic=23.4 and J=20.0, our survey is sensitive to objects with masses from about 0.6 to 0.05Msol. The mass function of Praesepe rises from 0.6Msol down to 0.1Msol and then turns-over at ~0.1Msol. The rise observed is in agreement with the mass function derived by previous studies, including a survey based on proper motion and photometry. Comparing our mass function with that for another open cluster with a similar age, the Hyades (age ~ 600Myr), we see a significant difference. Possible reasons are that dynamical evaporation has not influenced the Hyades and Praesepe in the same way, or that the clusters did not have the same initial mass function, or that dynamical interactions have modified the evolution of one or both clusters. Although a difference in the binary fractions of the clusters could cause the observed (i.e. system) mass functions to differ, measurements in the literature give no evidence for a significant difference in the binary fractions of the two clusters. Of our cluster candidates, six have masses predicted to be equal to or below the stellar/substellar boundary at 0.072Msol.Comment: 11 pages, 11 figures, accepted for publication in A&A. Higher resolution of Figures 2-3-4-5 in A&A published version. Revised version corrected for Englis

Near-infrared spectra of ISO selected Chamaeleon I young stellar objects

We present 0.95--2.5 micron moderate (R = 500) resolution spectra of 19 ISOCAM detected sources in the Chamaeleon I dark cloud. Thirteen of these stars are candidate very low mass members of the cloud proposed by Persi et al. (2000 A&A 357:219) on basis of the mid-IR color excess. The sample also includes a bona-fide young brown dwarf (Cha Halpha 1), a transition --stellar/sub-stellar-- object (Cha Halpha 2), one previously known T Tauri star (Sz 33) and three ISOCAM sources with no mid-IR excess. The spectra of the mid-IR color excess sources are relatively flat and featureless in this wavelength range. Both atomic and molecular lines (when in absorption) are partially veiled suggesting the presence of continuum emission from circumstellar dust. In addition some of the sources show Paschen and Brackett lines in emission. We apply the 2 micron water vapor index defined by Wilking et al. (1999 AJ 117:469) to estimate spectral types. These stars have spectral types M0--8. We use Persi et al.'s stellar luminosity determinations, in combination with D'Antona & Mazzitelli latest pre-main sequence evolutionary tracks, to estimate masses and ages. The ISOCAM detected mid-IR excess sources have sub-solar masses down to the H-burning limit and a median age of few x 10^6 yr, in good agreement with the higher mass members of this cloud.Comment: Preprint in Manuscript format; 30 pages including 10 figure

Optical spectra of selected Chamaeleon I young stellar objects

We present optical spectra of eight candidate brown dwarfs and a previously known T Tauri star (Sz 33) of the Chamaeleon I dark cloud. We derived spectral types based on the strength of the TiO or VO absorption bands present in the spectra of these objects as well as on the PC3 index of Martin et al. (1999). Photometric data from the literature are used to estimate the bolometric luminosities for these sources. We apply D'Antona & Mazzitelli (1997) pre-main sequence evolutionary tracks and isochrones to derive masses and ages. Based on the presence of Halpha in emission, we confirm that most of the candidates are young objects. Our sample however includes two sources for which we can only provide upper limits for the emission in Halpha; whereas these two objects are most likely foreground/background stars, higher resolution spectra are required to confirm their true nature. Among the likely cloud members, we detect one new sub-stellar object and three transition stellar/sub-stellar sources.Comment: 22 pages - manuscript forma

Young Exoplanet Transit Initiative (YETI)

We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6m telescopes around the world to monitor continuously young (< 100 Myr), nearby (< 1 kpc) stellar clusters mainly to detect young transiting planets (and to study other variability phenomena on time-scales from minutes to years). The telescope network enables us to observe the targets continuously for several days in order not to miss any transit. The runs are typically one to two weeks long, about three runs per year per cluster in two or three subsequent years for about ten clusters. There are thousands of stars detectable in each field with several hundred known cluster members, e.g. in the first cluster observed, Tr-37, a typical cluster for the YETI survey, there are at least 469 known young stars detected in YETI data down to R=16.5 mag with sufficient precision of 50 milli-mag rms (5 mmag rms down to R=14.5 mag) to detect transits, so that we can expect at least about one young transiting object in this cluster. If we observe 10 similar clusters, we can expect to detect approximately 10 young transiting planets with radius determinations. The precision given above is for a typical telescope of the YETI network, namely the 60/90-cm Jena telescope (similar brightness limit, namely within +/-1 mag, for the others) so that planetary transits can be detected. For planets with mass and radius determinations, we can calculate the mean density and probe the internal structure. We aim to constrain planet formation models and their time-scales by discovering planets younger than 100 Myr and determining not only their orbital parameters, but also measuring their true masses and radii, which is possible so far only by the transit method. Here, we present an overview and first results. (Abstract shortened)Comment: 15 pages, 10 figures, AN accepted 2011 June 1

Appendix 2: Water Quality Monitoring Project for Demonstration of Canal Remediation Methods Florida Keys- Report #1: Canal Water Characterization

Appendix to Water Quality Monitoring Project for Demonstration of Canal Remediation Methods, Florida Keys- Report #1: Canal Water Characterizaton This report serves as a summary of our efforts to date in the execution of the Water Quality Monitoring Project for Demonstration of Canal Remediation Methods, and a channel to deliver the datasets generated during field and laboratory measurements. The period of record for this report is Mar. 2014 – Dec. 2014 and includes data from two sampling events. The objective of the project is to provide data needed to make unbiased, statistically rigorous statements about the status and temporal trends of water quality parameters in the remediated canals. The execution of the project includes two phases: 1) Characterization of canal waters before remediation; and 2) monitoring water quality changes after remediation. We have completed the phase of data collection for the Characterization stage with two measuring/sampling campaigns. Characterization was accomplished using three data-gathering techniques, measuring vertical profiles (casts), continuous 24-hour recording (diel) of physicalchemical properties, and water sampling and analysis for nutrients. We deployed multisensor, water quality monitoring instruments (SeaBird CTD and YSI) to measure physicochemical parameter of at least two profiles throughout the water column at each canal, to generate depth profiles of each parameter. We also deployed pairs of YIS sondes to continuously measure physical-chemical variables of water quality during 24- hours. Finally, we collected and analyzed surface and bottom water samples

2014 Annual Report of the Water Quality Monitoring Project for the Water Quality Protection Program of the Florida Keys National Marine Sanctuary

This report serves as a summary of our efforts to date in the execution of the Water Quality Monitoring Project for the FKNMS as part of the Water Quality Protection Program. The period of record for this report is Mar. 1995 – Dec. 2014 and includes data from 78 quarterly sampling events within the FKNMS. This annual report reflects funding cutbacks in 2012 resulting in reduction of spatial sampling from 155 to 112 sites. Field parameters measured at each station (surface and bottom at most sites) include salinity (practical salinity scale), temperature (ºC), dissolved oxygen (DO, mg l-1), turbidity (NTU), relative fluorescence, and light attenuation (Kd, m-1). Water quality variables include the dissolved nutrients nitrate (NO3-), nitrite (NO2-), ammonium (NH4+), and soluble reactive phosphorus (SRP). Total unfiltered concentrations include those of nitrogen (TN), organic carbon (TOC), phosphorus (TP), silicate (SiO2) and chlorophyll a (CHLA, μg l-1). The EPA developed Strategic Targets for the Water Quality Monitoring Project (SP-47) which state that beginning in 2008 through 2012, they shall annually maintain the overall water quality of the near shore and coastal waters of the FKNMS according to 2005 baseline. For reef sites, chlorophyll a should be less than or equal to 0.35 μg l-1 and the vertical attenuation coefficient for downward irradiance (Kd, i.e., light attenuation) should be less than or equal to 0.20 m-1. For all monitoring sites in FKNMS, dissolved inorganic nitrogen should be less than or equal to 0.75 μM (0.010 ppm) and total phosphorus should be less than or equal to 0.25 μM (0.0077 ppm). Table 1 shows the number of sites and percentage of total sites exceeding these Strategic Targets for 2014. We must recognize that the reduction of sampling sites in western FKNMS (less human-impacted sites) and the increase in inshore sites (heavily human-impacted sites) introduces a bias to the dataset which results in a reporting problem, perhaps requiring a revision of SP-47 to correct this deviation. To avoid such complications, we have not included the recently added locations (#500 to #509) in the calculation of compliances. For reef stations, chlorophyll less than or equal to 0.35 micrograms liter-1 (ug l-1) and vertical attenuation coefficient for downward irradiance (Kd, i.e., light attenuation) less than or equal to 0.20 per meter; for all stations in the FKNMS, dissolved inorganic nitrogen less than or equal to 0.75 micromolar and total phosphorus less than or equal to 0.25 micromolar; water quality within these limits is considered essential to promote coral growth and overall health. The “number of samples” exceeding these targets is tracked and reported annually. Values in green are those years with % compliance greater than 1995-2005 baseline. Values in yellow are those years with % compliance less than 1995-2005 baseline

2013 Annual Report of the Water Quality Monitoring Project for the Water Quality Protection Program of the Florida Keys National Marine Sanctuary

This report serves as a summary of our efforts to date in the execution of the Water Quality Monitoring Project for the FKNMS as part of the Water Quality Protection Program. The period of record for this report is Mar. 1995 – Dec. 2013 and includes data from 73 quarterly sampling events within the FKNMS. This annual report reflects funding cutbacks in 2012 resulting in reduction of spatial sampling from 155 to 112 sites. Field parameters measured at each station (surface and bottom at most sites) include salinity (practical salinity scale), temperature (ºC), dissolved oxygen (DO, mg l‐1), turbidity (NTU), relative fluorescence, and light attenuation (Kd, m‐1). Water quality variables include the dissolved nutrients nitrate (NO3 ‐), nitrite (NO2 ‐), ammonium (NH4 +), and soluble reactive phosphorus (SRP). Total unfiltered concentrations include those of nitrogen (TN), organic carbon (TOC), phosphorus (TP), silicate (SiO2) and chlorophyll a (CHLA, μg l‐1). The EPA developed Strategic Targets for the Water Quality Monitoring Project (SP‐47) which state that beginning in 2008 through 2012, they shall annually maintain the overall water quality of the near shore and coastal waters of the FKNMS according to 2005 baseline. For reef sites, chlorophyll a should be less than or equal to 0.2 μg l‐1 and the vertical attenuation coefficient for downward irradiance (Kd, i.e., light attenuation) should be less than or equal to 0.13 m‐1. For all monitoring sites in FKNMS, dissolved inorganic nitrogen should be less than or equal to 0.75 μM (0.010 ppm) and total phosphorus should be less than or equal to 0.2 μM (0.0077 ppm). Table 1 shows the number of sites and percentage of total sites exceeding these Strategic Targets for 2013. We must recognize that the reduction of sampling sites in western FKNMS (less human‐impacted sites) and the increase in inshore sites (heavily human‐impacted sites) introduces a bias to the dataset which results in a reporting problem, perhaps requiring a revision of SP‐47 to correct this deviation. To avoid such complications, we have not included the recently added locations (#500 to #509) in the calculation of compliances

2015 Annual Report of the Water Quality Monitoring Project for the Water Quality Protection Program of the Florida Keys National Marine Sanctuary

This report serves as a summary of our efforts to date in the execution of the Water Quality Monitoring Project for the FKNMS as part of the Water Quality Protection Program. The period of record for this report is Apr. 1995 – Dec. 2015 and includes data from 82 quarterly sampling events within the FKNMS (20.5 years). This annual report reflects funding cutbacks in 2012 resulting in reduction of spatial sampling from 155 to 112 sites. Field parameters measured at each station (surface and bottom at most sites) include salinity (practical salinity scale), temperature (ºC), dissolved oxygen (DO, mg l-1), turbidity (NTU), relative fluorescence, and light attenuation (Kd, m-1). Water quality variables include the dissolved nutrients nitrate (NO3-), nitrite (NO2-), ammonium (NH4+), and soluble reactive phosphorus (SRP). Total unfiltered concentrations include those of nitrogen (TN), organic carbon (TOC), phosphorus (TP), silicate (SiO2) and chlorophyll a (CHLA, μg l-1). The EPA developed Strategic Targets for the Water Quality Monitoring Project (SP-47) which state that beginning in 2008 through 2015, they shall annually maintain the overall water quality of the near shore and coastal waters of the FKNMS according to 2005 baseline. For reef sites, chlorophyll a should be less than or equal to 0.35 μg l-1 and the vertical attenuation coefficient for downward irradiance (Kd, i.e., light attenuation) should be less than or equal to 0.20 m-1. For all monitoring sites in FKNMS, dissolved inorganic nitrogen should be less than or equal to 0.75 μM (0.010 ppm) and total phosphorus should be less than or equal to 0.25 μM (0.0077 ppm). Table 1 shows the number of sites and percentage of total sites exceeding these Strategic Targets for 2015. We must recognize that the reduction of sampling sites in western FKNMS (less human-impacted sites) and the increase in inshore sites (heavily human-impacted sites) introduces a bias to the dataset which results in a reporting problem, perhaps requiring a revision of SP-47 to correct this deviation. To avoid such complications, we have not included the recently added locations (#500 to #509) in the calculation of compliances. For reef stations, chlorophyll less than or equal to 0.35 micrograms liter-1 (ug l-1) and vertical attenuation coefficient for downward irradiance (Kd, i.e., light attenuation) less than or equal to 0.20 per meter; for all stations in the FKNMS, dissolved inorganic nitrogen less than or equal to 0.75 micromolar and total phosphorus less than or equal to 0.25 micromolar; water quality within these limits is considered essential to promote coral growth and overall health. The “number of samples” exceeding these targets is tracked and reported annually. Values in green are those years with % compliance greater than 1995-2005 baseline. Values in yellow are those years with % compliance less than 1995-2005 baseline

Water Quality Monitoring Project for Demonstration of Canal Remediation Methods: Florida Keys

Several important results have been realized from FIU’s regional monitoring project. First is the documentation of elevated nutrient concentrations (DIN, TP and SiO2) in waters close to shore along the Keys, and corresponding responses from the system, such as higher phytoplankton biomass (CHLA), turbidity and light attenuation (Kd), as well as lower oxygenation (DO) and lower salinities of the water column. These changes, associated to human impact, have become more obvious in a new series of ten stations (# 500 to #509) located very close to shore, near canal mouths and sampled since November 2011 (SHORE; Fig 4). These waters are part of the so called Halo Zone, a belt following the shoreline which extends up to 500 meters offshore, and whose water quality characteristics are closely related to those in canals and affected by quick movement of infiltrated runoff and wastewaters (septic tanks), tides and high water tables Many canals do not meet the State’s minimum water quality criteria and are a potential source of nutrients and other contaminants to near shore waters designated as Outstanding Florida Waters. Hence, the Monroe County BOCC has approved moving forward with a series of canal restoration demonstration projects whose results will be used to further define restoration costs and for information in future grant applications to state and federal sources. The Monroe County, the WQPP Steering Committee and the Canal Subcommittee have selected ten (10) canals out of twenty (20) pre-selected sites, for demonstration of restoration technologies (See Summary in Table 4). The main objective of this demonstration is to obtain realistic data and costs for future restoration planning and grant application purposes (AMEC 2012). Those technologies under consideration target two fundamental problems, poor circulation (stagnation) and accumulation of organic matter. Both, poor circulation and accumulation of organic debris, besides run-off and seepage from septic tanks, are major contributors to water quality degradation in the Florida Keys (Kruczynski, 1999), especially to the degradation of canal waters