Alexei Kniazev

(SDSS projects in collaboration with Grebel, E.K., Zucker, D.B., Bell, E.F., Rix, H.-W., Holtzman, J., D. Martinez-Delgado)

We developed a method to identify planetary nebula (PN) candidates in imaging data of the Sloan Digital Sky Survey (SDSS). This method exploits the SDSS' five-band sampling of emission lines in PN spectra, which results in a color signature distinct from that of other sources and can be applied to galaxies where PNe appear as point sources. We tested this method with SDSS data of M31. In areas searched by previous authors, we were able to recover about 6/7 of the earlier known PNe. We are continuing our work on M31, and are in the process of extending it to other nearby galaxies to the extent possible. The ultimate goals of this work are to use PNe as tracers of kinematics in large galaxies where they are sufficiently numerous (e.g., in M31) and of chemical evolution (feasible even in low-mass galaxies where only 1-2 PNe are detected).

M31 Stellar Substructure in the SDSS Data: The spatial distribution of all stars with 21 < i < 22, with an inset optical image of M31 to scale. The arrows indicate major halo substructures: the northern spur (NS), the giant stream (GS) and the G1 clump (G1C). Anromeda NE's center is located at about (3,0.5) (From Zucker, D.B., Kniazev, A.Y. et al., New Giant Stellar Structure Near the Outer Halo of M31: Satellite or Stream?, 2004, ApJ, 612, 117L).

The spatial distribution of all selected PNe candidates from M31 SDSS data. The figure coordinates are the same as for Figure above. X and Y are in arcdegrees from the center of M31, along the major and minor axes, respectively. With blue triangles all stellar PNe candidates of the first priority are shown. With red filled circles all stellar PNe candidates of the first priority that were identified from the earliest works are shown. With pink triangles all stellar PNe candidates of the second priority are shown. With yellow diamonds all extended PNe candidates of the second priority are shown. With green diamonds all extended PNe candidates of the first priority are shown.

Last News (14.10.2004): For follow up spectroscopy of selected PNe candidates from M31 SDSS data we had requested and had got 4+4 nights of Service Mode Rank A observations with CAFOS instrument is installed at the 2.2m telescope at Calar Allto Observatory (Spain). After 8 nights of observations with poor weather (average seeing from 2.0 to 2.5 arcsec) 86 candidates were observed: 9 are well-known PNe to calibrate our data, 52 of stellar PNe candidates of the first priority, 14 of stellar PNe candidates of the second priority, and 17 of extended candidates of the first and the second priority that were located at the largest distances from the center of M31. The observations have finished. We have currently the next results: 86 of our candidates were observed in total; 77 of them are really new candidates (not from well-known list); 45 of stellar PNe candidates of the first priority from 52 newly observed candidates are real PNe and our selection rate for such kind of objects is 87% 11 of stellar PNe candidates of the second priority from 11 newly observed candidates are real PNe and our selection rate for such kind of objects is 79% 5 of extended PNe candidates of the first priority from 8 newly observed candidates are real PNe and our selection rate for such kind of objects is 63% Our method of PNe selection from SDSS-data really works! We have found two PNe in the area of Andromeda NE! These PNe are located at the projected distances ~48 Kpc and ~41 Kpc from the center of M31. We have also found one more distant PN at the SW part of M31 with projected distance ~37.5 Kpc from the center.

Figure: The spatial distribution of observed PNe candidates from SDSS M31 data. The figure coordinated are the same as for Figures above.š The black ellipse indicates the extend and inclination of M31's disc, and the location of NGC205, M32 and Andromeda NE are also marked with big black circles. The blue ellipse indicates the area of location of PNe from the disc of M31 that were found with Planetary Nebula Spectrograph (was calculated from Figure 1 of Merrett et al., MNRAS, 2003,346,L62). With small circles all our stellar PNe candidates of the first priority are shown. With filled small circles all known PNe from the our sample are shown (all of them are from the first priority candidates). With black crosses all stellar PNe candidates of the second priority are shown. With triangles and squares all extended PNe candidates of the first and the second priority are shown. PNe candidates that after observations appeared as real PNe are shown with red crosses. PNe candidates that after observations did not appeared as any emission-line objects are shown with blue crosses. PNe candidates that after observations appeared as emission-line galaxies are shown with green crosses (PS-version of this Figure).

(In collaboration with Grebel, E.K., Pustilnik, S.A., Pramsky, A.G.)

We present the first results of NTT spectroscopy of HII regions and PNe in three dwarf galaxies in the nearby Antlia-Sextans poor group of galaxies: Sextans A, Sextans B and NGC 3109. For the most PNe and HII regions in these galaxies O,N,Ne,S,Ar and He abundances have been obtained with the classic Te-method after the detection of the [OIII] 4364 A line.