8201( 7) - 04/22/99 11:23 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8201 Version: 7 Check-in Date: 22-Apr-1999 11:22:33 1.Proposal Title: The Ultraviolet Properties of Ultra- Luminous Infrared Galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Gerhardt Meurer The Johns Hopkins University CoI: Dr. Jeffrey D. Goldader The University of Pennsylvania N CoI: Prof. David Sanders IFA, University of Hawaii N CoI: Prof. Timothy M. Heckman The Johns Hopkins University N CoI: Dr. Charles C. Steidel The California Institute of Technology N CoI: Dr. Daniela Calzetti Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract Ultraluminous Infrared Galaxies (ULIRGs) are the most luminous galaxies known in the local universe, and are predominantly powered by massive star formation. ULIRGs are the only type of star forming galaxies in the local universe with bolometric luminosities approaching those of the Lyman-dropout systems and SCUBA sub-mm detections at z ~ 3. However, very few observations of ULIRGs exist at ultraviolet (UV) wavelengths to compare to these high-z detections. Here we propose imaging a modest size sample of ULIRGs in the UV with STIS. This will extend the observations of these objects into the wavelength range where massive stars dominate the intrinsic spectrum. We will then be better able to compare the rest- frame UV morphology and overall SEDs of ULIRGs to the high-z systems. We will test whether transmitted UV light traces star formation and whether the UV SED reddens with dust absorption as is the case for UV selected starbursts. We will assess what impact ULIRGs make o n rest-frame UV surveys of galaxies. Our images combined with archival optical to near IR images will build on the HST heritage allowing key issues concerning the physics of ULIRGs to be addressed. These include the relative importance of clustered versus diffuse star formation, the mechanism of star formation feedback, and whether and how UV light escapes these dusty systems. ------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 2] Observations Description ------------------------ We propose obtaining observations of seven ULIRGs in two ultraviolet bands using STIS. The sample galaxies are listed in Table 1. They were chosen from the ``IRAS Bright Galaxy Sample'' (Soifer et al.\ 1987) to have L_bol > 10^11.5 L_\odot, IRAS flux densities at 60 and 100 Mum >~ 5 Jy, and A_B( Gal) < 0.3 mag. The minimum L_bol is 0.5 dex lower than the standard ULIRG definition so as to better close the gap with the UV selected sample (see Fig. 1) and to better cover the L range of the HDF U-dropout sample. With the 4 galaxies of similar L_bol observed by T98 and M95 a total of 11 ULIRGs will have been imaged in the UV by HST. This is a modest size sample, comparable in size to the UV selected starburst sample of Meurer et al.\ (1995), and will be sufficient to determine mean properties and note gross trends. We have excluded galaxies with warm 25 to 60 micron flux ratios as the dust in these are likely to be strongly heated by AGN which is not that common in ULIRGs. H owever our sample does include galaxies spectroscopically classified as Seyfert 2 and/or LINER. Our primary goals for this sample are (1) extending the SEDs into the UV; (2) determining their reddening properties; and (3) determining the UV morphology. The Hubble Space Telescope is the only telescope that can be used to achieve these goals since the vacuum UV is inaccessible from the ground, and because of its high resolution imaging ability. The ULIRGs in our sample are thought to be powered predominantly by circumnuclear starbursts with <~ kiloparsec scale sizes that project to only a few arcseconds. Our experience is that starbursts contain numerous compact star clusters separated by tens of parsecs (M95). These structures can be discerned in ULIRGs over the z range of our sample (T98). We will use our images to identify clusters and nuclei and determine their combined contribution to the transmitted UV flux. Observations in two UV bands are necessary to determine the U V color of the galaxies which is required for determining t heir reddening properties. The detector plus filter combinations best suited for this project are: FUVMAMA + F25SRF2 [1457, 283], and NUVMAMA + F25QTZ [2330, 945] (pivot wavelength, Lambda_p and effective Gaussian FWHM in Angstroms as determined by SYNPHOT are given in brackets). This combination of filters was chosen to have maximum throughput and provide adequate Lambda baseline for measuring the UV color. It has the added benefit of corresponding to observed frame V, I observations of galaxies at z ~ 2.5. In addition, the Lambda_p of the NUV filter is similar to that of the FOC F220W filter, allowing direct comparison with many previous observations (e.g.\ M95; T98; Maoz et al.\ 1996). The FUVMAMA + F25SRF2 (hereafter FUV) combination has negligible redleak due to the solar-blind nature of the CsI detectors. The NUVMAMA + F25QTZ (hereafter NUV) observations will have some sensitivity for Lambda > 3000Angstrom. Filters with better redleak protection are available but wi ll result in much lower count rates of UV photons (e.g.\ a factor of ten lower for F25CN182). We will use available optical imaging data (ground based and HST) to assess the amount of redleak in our observations. In addition our models for comparison (e.g.\ Fig. 4) will be derived from spectra out to the infrared and the latest filter transmission curves. Hence, the redleak will be folded into the models. Figure 4 illustrates how we will determine the reddening properties of ULIRGs. It plots log(F_FIR/F_NUV) versus m_FUV - m_NUV (ABmag). We used SYNPHOT to determine that the photometric color can be directly transformed into UV spectral slope Beta (Beta ~ -2 + 1.96(m_FUV - m_nuv)) for both the local UV selected sample, and a wide range of star forming population models (Leitherer &\ Heckman 1995; Bruzual &\ Charlot 1993) convolved with starburst dust absorption models (Calzetti 1997; Kinney et al.\ 1994). Hence this figure is analogous to Fig. 2. The same UV selected sta rb urst sample is plotted with UV quantities measured from IUE spectra using SYNPHOT, and with F_FIR derived from IRAS fluxes. The lines show a variety of population plus dust absorption models. The solid line shows that a relatively grey reddening law may account for the reddening of ULIRGs like F12112+0305 (cf.\ Fig 2), within the present uncertainties. Our proposed observing strategy is to extract integrated fluxes from both the NUV and FUV images, thus producing the UV quantities required for the SED analysis and to construct Fig. 4. The NUV images are expected to have higher count-rates than the FUV images by a factor of a few, and will be obtained at a higher S/N for the morphological analysis. Our goals can be met using two orbits per galaxy, as illustrated in the following analysis. From the limited UV data on ULIRGs (i.e.\ Fig. 2) we expect typically Beta ~ 1 and F_FIR/F_220 ~ 400, while Table 1 shows that typically F_FIR ~ 2.5* 10^-10, erg cm^-2 s^- 1. (Note - here F_FIR is the FIR flux defined by Helou et al.\ (1988), w hi le the UV flux is a generalized flux of the form F_220 = Lambda f_Lambda = 2320 f_2320). Hence the flux densities of a typical ULIRG in our two bands will be f_FUV ~ 1.7 * 10^- 16, erg cm^-2 AA^-1 s^-1 arcsec^-2, f_NUV ~ 2.3 * 10^-16, erg cm^-2 AA^-1 s^-1. Following from Meurer et al.\ (1997) the median FIR effective surface brightness (that within the half light radius) of a starburst is S_e ~ 1.7 * 10^-11, erg cm^-2 s^-1, hence the area within half light radius is ~ 15, arcsec^2. Considering an average orbital visibility (54 min), and allowing for overheads we propose obtaining exposures of 1500s in the NUV and 3800s in the FUV. Employing these exposure times and integrating (half the flux) over the above effective area, we then calculate (with the exposure time calculator) S/N = 151 and 46 in the NUV and FUV respectively. The former is comparable to the image quality of the FOC images of Meurer et al.\ (1995). The need for two orbits per galaxy anticipates the most extr em ely reddened and extinguished objects. For the above expos ure times, half light radius, FIR surface brightness and F_FIR/F_220, then galaxies with Beta <~ 4.5 can be detected at S/N > 10 in the FUV. Similarly for the same NUV exposure time, half light radius and FIR surface brightness objects having F_FIR/F_220 <~ 10^4 can be detected to a S/N > 10 in the NUV. A S/N = 10 in each band results in an acceptable +/- 0.3 uncertainty in Beta. Since these are extended objects, the S/N per area estimate is not reduced for objects having higher FIR fluxes, hence the same number of orbits are requested for all objects. In Phase II we have specified ORIENT so that the ability to see extended structure is maximized. We dither the images so as to minimize the amount of light lost under the repeller wire (for the FUV MAMA observations) and to minimize the effects of flat-field blemishes. Since the sky background is likely to be highly variable during an orbit, we have limited the exposures to about 700s duration in order to allow us to isolate l ow background exposures. Real Time Justification ----------------------- There are no special requirements. Calibration Justification ------------------------- Additional Comments ------------------- As noted above, our target sample has extensive previous imaging at optical to near IR wavelengths both from the ground and with HST. Much of this data is already directly available to us, including some U band imaging. We plan more U band imaging with the Apache Point Observatory 3.5m and the CTIO 0.9m to obtain U images of all galaxies in our sample. The U band imaging will be used to asses whether any of the target galaxies, or nearby stars, are likely to exceed the STIS bright object limits. The U images will also give an indication of how much UV light may be falling outside the area of our STIS images. The optical- NIR data will be used to asses the amount of red leak in NUV mama observations, and to provide matched aperture SEDs of our sample (e.g.\ T98). As noted in the justification the multi-wavelength HST imaging data will allow us to map dust absorption and the ages of knots within the ULIRGs. ------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 3] Data Distribution Paper Products: YES Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS15327+23 GALAXY, ULTRALUMINOUS RA=15H 34M 57.23S +/- 1.0", J2000 V=+5434 V = 13.4+/-0.2 40 IR GAL, STARBURST, DEC=23D 30' 12.1" +/- 1.0" B = 14.00+/-0.1 NUCLEUS 2 IRAS01053- GALAXY, ULTRALUMINOUS RA=01H 7M 46.96S +/- 1.0", DEC=- J2000 V=+6016 V = 13.8+/-0.5 1746 IR GAL, STARBURST, 17D 30' 24.2" +/- 1.0" NUCLEUS 3 IRAS13428+56 GALAXY, ULTRALUMINOUS RA=13H 44M 42.09S +/- 1.0", J2000 V=+11272 V = 14.0+/-0.2 08 IR GAL, STARBURST, DEC=55D 53' 12.7" +/- 1.0" U = 15.12+/-0.15 NUCLEUS B = 14.69+/-0.1 4 IRAS13183+34 GALAXY, ULTRALUMINOUS RA=13H 20M 35.31S +/- 1.0", J2000 V=+7000 V = 13.9+/-0.5 23 IR GAL, STARBURST, DEC=34D 8' 27.3" +/- 1.0" NUCLEUS 5 IRAS08572+39 GALAXY, ULTRALUMINOUS RA=09H 0M 25.50S +/- 1.0", J2000 V=+17450 V = 14.4+/-0.5 15 IR GAL, STARBURST, DEC=39D 3' 52.6" +/- 1.0" U = 16.68+/-0.15 NUCLEUS B = 14.82+/-0.1 6 IRAS15250+36 GALAXY, ULTRALUMINOUS RA=15H 26M 59.43S +/- 1.0", J2000 V=+16602 V = 15.6+/-0.2 09 IR GAL, STARBURST, DEC=35D 58' 37.6" +/- 1.0" U = 16.21+/-0.15 NUCLEUS B = 16.17+/-0.1 7 IRAS19254- GALAXY, ULTRALUMINOUS RA=19H 31M 21.27S +/- 1.0", DEC= J2000 V=+18500 V = 15.7+/-0.5 7245 IR GAL, STARBURST, -72D 39' 16.8" +/- 1.0" NUCLEUS 8201( 7) - 04/22/99 11:23 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 170D TO 210D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS15327+2 STIS/N ACCUM F25QTZ MIRROR 1 750 S 340 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS15327+2 STIS/N ACCUM F25QTZ MIRROR 1 750 S POS TARG 0.24, 0.24 340 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS15327+2 STIS/F ACCUM F25SRF2 MIRROR 2 450 S POS TARG -0.24,-0.24 340 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS15327+2 STIS/F ACCUM F25SRF2 MIRROR 2 690 S POS TARG 0, 0 340 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 IRAS15327+2 STIS/F ACCUM F25SRF2 MIRROR 2 690 S POS TARG 0.24, 0.24 340 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 6] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS01053-1 STIS/N ACCUM F25QTZ MIRROR 1 750 S 746 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS01053-1 STIS/N ACCUM F25QTZ MIRROR 1 750 S POS TARG 0.24, 0.24 746 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS01053-1 STIS/F ACCUM F25SRF2 MIRROR 2 420 S POS TARG -0.24,-0.24 746 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS01053-1 STIS/F ACCUM F25SRF2 MIRROR 2 680 S POS TARG 0, 0 746 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 IRAS01053-1 STIS/F ACCUM F25SRF2 MIRROR 2 680 S POS TARG 0.24, 0.24 746 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 7] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS13428+5 STIS/N ACCUM F25QTZ MIRROR 1 750 S 608 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS13428+5 STIS/N ACCUM F25QTZ MIRROR 1 750 S POS TARG 0.24, 0.24 608 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS13428+5 STIS/F ACCUM F25SRF2 MIRROR 2 550 S POS TARG -0.24,-0.24 608 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS13428+5 STIS/F ACCUM F25SRF2 MIRROR 2 740 S POS TARG 0, 0 608 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 IRAS13428+5 STIS/F ACCUM F25SRF2 MIRROR 2 740 S POS TARG 0.24, 0.24 608 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 8] Visit: 04 Visit Priority: Visit Requirements: ORIENT 210D TO 230D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS13183+3 STIS/N ACCUM F25QTZ MIRROR 1 750 S 423 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS13183+3 STIS/N ACCUM F25QTZ MIRROR 1 750 S POS TARG 0.24, 0.24 423 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS13183+3 STIS/F ACCUM F25SRF2 MIRROR 2 450 S POS TARG -0.24,-0.24 423 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS13183+3 STIS/F ACCUM F25SRF2 MIRROR 2 700 S POS TARG 0, 0 423 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 IRAS13183+3 STIS/F ACCUM F25SRF2 MIRROR 2 700 S POS TARG 0.24, 0.24 423 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 9] Visit: 05 Visit Priority: Visit Requirements: ORIENT 150D TO 210D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS08572+3 STIS/N ACCUM F25QTZ MIRROR 1 750 S 915 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS08572+3 STIS/N ACCUM F25QTZ MIRROR 1 750 S POS TARG 0.24, 0.24 915 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS08572+3 STIS/F ACCUM F25SRF2 MIRROR 2 480 S POS TARG -0.24,-0.24 915 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS08572+3 STIS/F ACCUM F25SRF2 MIRROR 2 710 S POS TARG 0, 0 915 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 IRAS08572+3 STIS/F ACCUM F25SRF2 MIRROR 2 710 S POS TARG 0.24, 0.24 915 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 10] Visit: 06 Visit Priority: Visit Requirements: ORIENT 160D TO 180D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS15250+3 STIS/N ACCUM F25QTZ MIRROR 1 750 S 609 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS15250+3 STIS/N ACCUM F25QTZ MIRROR 1 750 S POS TARG 0.24, 0.24 609 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS15250+3 STIS/F ACCUM F25SRF2 MIRROR 2 480 S POS TARG -0.24,-0.24 609 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS15250+3 STIS/F ACCUM F25SRF2 MIRROR 2 710 S POS TARG 0, 0 609 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 IRAS15250+3 STIS/F ACCUM F25SRF2 MIRROR 2 710 S POS TARG 0.24, 0.24 609 UV-MAM EXPAND A ------------------------------------------------------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 11] Visit: 07 Visit Priority: Visit Requirements: ORIENT 30D TO 40D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS19254-7 STIS/N ACCUM F25QTZ MIRROR 1 750 S 245 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS19254-7 STIS/N ACCUM F25QTZ MIRROR 1 750 S POS TARG 0.24, 0.24 245 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS19254-7 STIS/F ACCUM F25SRF2 MIRROR 2 600 S POS TARG -0.24,-0.24 245 UV-MAM EXPAND END ORBIT A ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS19254-7 STIS/F ACCUM F25SRF2 MIRROR 2 500 S POS TARG -0.24,-0.24 245 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 IRAS19254-7 STIS/F ACCUM F25SRF2 MIRROR 2 510 S POS TARG 0, 0 EXPAND 245 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9 IRAS19254-7 STIS/F ACCUM F25SRF2 MIRROR 2 500 S POS TARG 0.24, 0.24 END 245 UV-MAM ORBIT A ------------------------------------------------------------------------------------------------------------------------------------ 8201( 7) - 04/22/99 11:23 - [ 12] Summary Form for Proposal 8201 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25QTZ F25SRF2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 170D TO 210D POS TARG 0.24, 0.24 POS TARG -0.24,-0.24 EXPAND POS TARG 0, 0 POS TARG 0.24, 0.24 EXPAND ORIENT 210D TO 230D ORIENT 150D TO 210D ORIENT 160D TO 180D ORIENT 30D TO 40D POS TARG -0.24,-0.24 EXPAND END ORBIT POS TARG -0.24,-0.24 POS TARG 0, 0 EXPAND POS TARG 0.24, 0.24 END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names IRAS15327+2340 IRAS01053-1746 IRAS13428+5608 IRAS13183+3423 IRAS08572+3915 IRAS15250+3609 IRAS19254-7245 ------------------------------------------------------------------------------------------------------------------------------------