Short Progress Report of the DENIS project

(November 2000)

 

Introduction

The DENIS project, started in December 1995, has progressed satisfactorily during 2000. At the end of the present year, the observations (i.e. an IJK colour coverage of the all sky at declinations : -88 < d < +2) will be completed to better than 90 % (see Fig.1).

No major instrumental failure has been reported this year, and the local operations team seconded by several visiting astronomers, mostly students from institutes in partner countries, has run the progamme under good conditions.

Progress of the observations

Figure 1 shows that the covered surface of the sky has increased by some 22% in one year. This rate has been nominal continuously and since the beginning, except during Summer 97-98 when several factors seriously hampered a satisfactorily progress, namely, lack of an operations engineer, poor meteorological conditions (El Niño), and important instrument modifications (new CCD dewar, and set up of a thermal control of the instrument optical box).

Figure 1 Progress of the DENIS observations

 

Figure 2 displays the repartition of the observed surface per boxes of one hour of RA. This diagram immediately shows that, not unexpectedly, the "Summer" zone is better completed than the "Winter" one. Since the galactic bulge, one of the key project of DENIS, is mostly a "Winter" target, it would be extremely important to complete the observations in Winter 2001 in the RA range 16-19 hours.

Figure 2 Coverage of DENIS by RA boxes (as of Oct 15, 2000)

Progress of the data processing in the Data Analysis Centers.

Data processing has considerably progressed at both official sites in 2000. The LDAC, in Leiden, mainly focussed on the preparation of the Point Source Catalogues of the Magellanic Clouds (see below) and started recently to run an improved pipeline which is now currently and routinely operated.

The PDAC, in Paris, has also improved its reduction pipeline, including a point source extraction algorithm and an automatic input toward a home-made data base for point sources. Image processing, point source extraction and storage in this working database are done now in a single pass. Strong effort has been made to set quality criteria to the data, in particular regarding the PSF values and fluctuations, in order to put on side lower quality data and to flag 'strips' that must be re-observed now. Finally, the extended source pipeline has been put in operation and has already yielded some 600,000 galaxies over 3000 square degrees of analysed sky. Other algorithms aimed at selecting faint sources such as brown dwarfs and low mass stars have been implemented and are running successfully (see below)

Table: summary of the progress of the data processing

 

Fraction of sky covered (Dec. 2000)

92 %

Fraction of images processed at PDAC

80 %

Fraction of sky processed for point source extraction at PDAC

30 %

Fraction of sky processed for point source extraction in Leiden

20 %

Fraction of sky processed for galaxy extraction at PDAC

13 %

 

The Centre de Données astronomiques de Strasbourg (CDS) proceeds with providing on-line access to the point source catalogues (so far, mostly coming from Leiden, but, soon to come, those extracted in Paris). A user friendly web server has been implemented (http://cdsweb.u-strasbg.fr/denis.html). A first data release occurred in December 1998. Magellanic Clouds data access has been opened to the public in January 2000, and another large public release is planned in December 2000. DENIS point source catalogues are incorporated in the CDS services, Vizier and ALADIN, thus allowing easy identification with other on-line catalogues.

 

Main scientific results of DENIS (1999-2000)

18 refereed articles based on DENIS observations have been published during the last 2 years, 78 publications with the word DENIS in their titles are reported in the ADS for the last 5 years (1996-2000) (to be compared to the 65 publications with the word 2MASS in the same period). Several groups have proceeded with the scientific analysis and exploitation of the data in the various fields of interest, as briefly summarised below.

Brown dwarfs and low mass stars

DENIS has discovered the first sample of free-floating brown dwarfs together with 2MASS, e.g. DENIS P-J 1228.2-1547 has become an archetypical example of this species of objects. The great advantage of DENIS vs. 2MASS is to provide the I band photometry together with the NIR magnitudes. The extraction of very faint and red sources is however challenging and extraction of bona fide samples of BDs and VLMs has been improved. Good collaboration with Keck telescope teams has allowed to increase the number of known BD and VLM stars (Martin et al., 1999a,b). The closest known dM9 star has been recently singled out (Delfosse et al., 2000, see also: recent observations at ESO, Nov. 20, 2000)

Galactic Bulge populations

Merging DENIS NIR data and ISOCAM data at 7 et 15 m on several fields that sample the galactic bulge and disk at various longitudes and latitudes - the ISOGAL program - has led to important results on the classification of the stellar populations of the bulge and the separation of young and old populations. For the first time, a large sample of RGB stars with weak mass loss has been singled out (Omont et al., 1999).

Repeated DENIS observations have been used to look for variable stars. 1000 probable variables in an area of ~ 4 deg2 of the inner galactic bulge have been detected. The first one contains ~ 720 variable star candidates which show variability in J and KS while the second consists of sources only observed to be variable in KS (~ 270 sources), mainly in regions with high interstellar extinction. Most of the variable stars are found to be above the RGB tip and thus belong to the AGB. The AGB variables can be distinguished from other M-type giants by their high 7m luminosities and redder K0-[7] colours. (Schultheis et al., 2000).

 

Galactic structure, stellar statistics and interstellar extinction

Following preliminary works published in the early years of DENIS (e.g., Ruphy PhD Paris, 1996), new studies are underway that make use of DENIS data to constrain models of stellar population synthesis in the Galaxy (Derriere, PhD, Strasbourg, 2000). DENIS observations in J and K together with isochrones calculated for the RGB and AGB phases have been used to draw an extinction map of the inner Galactic Bulge. The uncertainty in this method is mainly limited by the optical depth of the Bulge itself. A comparison with fields of known extinction shows a very good agreement. An extinction map for the inner Galactic Bulge has been drawn () (Schultheis et al., 1999)

 

Star formation in Giant Molecular Clouds

NIR surveys are essential tools to pick up young stellar objects embedded in dust clouds. A systematic investigation of the most nearby Southern GMCs is underway that includes the Cham, Oph, Lup, Orion, the Coal Sack etcA preliminary work was done by Cambrésy in 1998 (and PhD thesis, Paris 1999) in the Chamaeleon Cloud leading to the detection of about 50 new T Tau candidates and identifying a handful of young brown dwarfs. A wider field involving all components of the Cham. Complex is now investigated (thesis M. Vuong, Nice in progress)

 

Magellanic Clouds

The point source catalogues of the Large and Small Magellanic Clouds have been published and are now released for wide use (Cioni et al., 2000a; Cioni, PhD, Leiden, 2001). Public access is provided by the Centre de Données Astronomiques de Strasbourg (http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=DCMC). The LMC and SMC catalogues contain more than 1.3 million and more than 300 000 sources, respectively. Papers based on a preliminary analysis of this huge data base have been published, one deals with a new estimation of the distance of the MC's based on the estimation of the luminosity function of the RGB stars (Cioni et al., 2000b), the other on the different morphology of the MCs seen when one considers young or old populations. (Cioni et al., 2000c).

 

Extragalactic

The NIR surveys, and DENIS in particular, are very important for cosmology because the galaxies selected in this spectral domain allow to probe the mass distribution in the local Universe (low dust extinction in our Galaxy and in the galaxies, less sensitivity to recent star formation compared to optical or FIR). Effort has been put on the implementation of a reliable extraction pipeline at PDAC and first publication of some 300,000 galaxies is expected in January 2001 (Mamon et al., in preparation).

Visual identification of galaxies in the zone of avoidance is still in progress in Nice and Lyon (Schroeder et al., 1999, Rousseau et al., 2000). An HI follow up survey of the DENIS galaxies is also underway at Nançay radiotelescope and a merged catalogue of DENIS and 2MASS galaxies will serve as input catalogue for the Australian 6dF project .

Needs for completing the DENIS survey

DENIS, together with 2MASS, is the reference near IR sky survey in the Southern hemisphere. Apart from the science that they have and will achieve, they provide also extremely useful tools for the preparation of future space or ground based observations (VLT,VLTI) as the Schmidt plates did in the past. 2MASS and DENIS complement each other in their overlapping areas, observations have been done at different epochs, and can be compared to pick up variable objects, and most importantly DENIS provides the only comprehensive survey in the I band with a spatial resolution of one arsecond, while 2MASS has a resolution of only 2 arsec in the 3 bands JHK.

2MASS will be complete and reliable up to about 99 % and it is important that DENIS be completed also up to a comparable level (at least complete and reliable up to more than 95%). Considering that the completion will be about 92 % at the end of December 2000 and that a number of strips must be redone because of bad observing conditions, an extension of the observations for a period of about 6 months, spread over the year is highly desirable.

Refereed Publications (1999-2000)

Cioni, M.-R.; Loup, C.; Habing, H. J.; Fouqué, P.; Bertin, E.; Deul, E.; Egret, D.; Alard, C.; de Batz, B.; Borsenberger, J.; Dennefeld, M.; Epchtein, N.; Forveille, T.; Garzón, F.; Hron, J.; Kimeswenger, S.; Lacombe, F.; Le Bertre, T.; Mamon, G. A.; Omont, A.; Paturel, G.; Persi, P.; Robin, A.; Rouan, D.; Simon, G.; Tiphène, D.; Vauglin, I.; Wagner, S., 2000a, The DENIS Point Source Catalogue towards the Magellanic Clouds, 2000A&AS..144..235C

Cioni, M.-R. L.; van der Marel, R. P.; Loup, C.; Habing, H. J, 2000b, The tip of the red giant branch and distance of the Magellanic Clouds: results from the DENIS survey, 2000A&A...359..601C

Cioni, M.-R. L.; Habing, H. J.; Israel, F. P, 2000c, The morphology of the Magellanic Clouds revealed by stars of different age: results from the DENIS survey, 2000A&A...358L...9C

Delfosse, X.; Tinney, C. G.; Forveille, T.; Epchtein, N.; Borsenberger, J.; Fouqué, P.; Kimeswenger, S.; Tiphène, D.--Searching for very low-mass stars and brown dwarfs with DENIS 1999A&AS..135...41D-

Delfosse, X., Forveille T., Martin E., Guibert J., Borsenberger J., Crifo F., Alard C., Epchtein N., Fouqué P., Simon G., 2000, New Neighbours: II a M9 dwarf at d = 3.35 pc, DENIS-PJ 104814.7- 395606.1 - A&AL. in press

 

Epchtein, N.; Deul, E.; Derriere, S.; Borsenberger, J.; Egret, D.; Simon, G.; Alard, C.; Balázs, L. G.; de Batz, B.; Cioni, M.-R.; Copet, E.; Dennefeld, M.; Forveille, T.; Fouqué, P.; Garzón, F.; Habing, H. J.; Holl, A.; Hron, J.; Kimeswenger, S.; Lacombe, F.; Le Bertre, T.; Loup, C.; Mamon, G. A.; Omont, A.; Paturel, G.; Persi, P.; Robin, A. C.; Rouan, D.; Tiphène, D.; Vauglin, I.; Wagner, S. J.--A preliminary database of DENIS point sources, 1999A&A...349..236E

Fouqué, P.; Chevallier, L.; Cohen, M.; Galliano, E.; Loup, C.; Alard, C.; de Batz, B.; Bertin, E.; Borsenberger, J.; Cioni, M. R.; Copet, E.; Dennefeld, M.; Derriere, S.; Deul, E.; Duc, P.-A.; Egret, D.; Epchtein, N.; Forveille, T.; Garzón, F.; Habing, H. J.; Hron, J.; Kimeswenger, S.; Lacombe, F.; Le Bertre, T.; Mamon, G. A.; Omont, A.; Paturel, G.; Pau, S.; Persi, P.; Robin, A. C.; Rouan, D.; Schultheis, M.; Simon, G.; Tiphène, D.; Vauglin, I.; Wagner, S. J., 2000, An absolute calibration of DENIS (deep near infrared southern sky survey), 2000A&AS..141..313F

Kimeswenger, S.; Koller, J.; Schmeja, S., 2000, New identification of the near infrared source in the "born-again" planetary nebula A58 (=V605 Aql), 2000A&A...360..699K

Martín, Eduardo L.; Delfosse, Xavier; Basri, Gibor; Goldman, Bertrand; Forveille, Thierry; Zapatero Osorio, Maria Rosa, 1999a, Spectroscopic Classification of Late-M and L Field Dwarfs, 1999AJ....118.2466M

Martin, E. L.; Brandner, W.; Basri, G., 1999b, A Search for Companions to Nearby Brown Dwarfs: The Binary DENIS-P J1228.2-1547, 1999Sci...283.1718M--

Omont, A.; Ganesh, S.; Alard, C.; Blommaert, J. A. D. L.; Caillaud, B.; Copet, E.; Fouqué, P.; Gilmore, G.; Ojha, D.; Schultheis, M.; Simon, G.; Bertou, X.; Borsenberger, J.; Epchtein, N.; Glass, I.; Guglielmo, F.; Groenewegen, M. A. T.; Habing, H. J.; Kimeswenger, S.; Morris, M.; Price, S. D.; Robin, A.; Unavane, M.; Wyse, R.--ISOGAL-DENIS detection of red giants with weak mass loss in the Galactic bulge, 1999A&A...348..755O

Rousseau J., Paturel G., Vauglin I., Schroeder A., de Batz B., Borsenberger J., Epchtein N., Fouqué P., Kimeswenger S., Lacombe F., Le Bertre T., Mamon G., Rouan D., Simon G., Tiphène D., 2000, Some noteworthy DENIS galaxies near the galactic plane, A&A, in press

Schroeder, A.; Kraan-Korteweg, R. C.; Mamon, G. A., DENIS observations of multibeam galaxies in the Zone of Avoidance 1999PASA...16...42S-

Schultheis, M.; Ganesh, S.; Simon, G.; Omont, A.; Alard, C.; Borsenberger, J.; Copet, E.; Epchtein, N.; Fouqué, P.; Habing, H.--Interstellar extinction towards the inner Galactic Bulge, 1999A&A...349L..69S--

Schultheis, M.; Ganesh, S.; Glass, I. S.; Omont, A.; Ortiz, R.; Simon, G.; van Loon, J. Th.; Alard, C.; Blommaert, J. A. D. L.; Borsenberger, J.; Fouqué, P.; Habing, H. J., DENIS and ISOGAL properties of variable star candidates in the Galactic Bulge, 2000A&A...362..215S

Vauglin, I.; Paturel, G.; Borsenberger, J.; Fouqué, P.; Epchtein, N.; Kimeswenger, S.; Tiphène, D.; Lanoix, P.; Courtois, H., First DENIS I-band extragalactic catalog,  1999A&AS..135..133V-

Vavrek, R., Balazs, L., Epchtein N., 2000, Multifractal extinction filtering: application to the DENIS data in the Chamaeleon I cloud (A&A, in press)