An Atlas of PHT 2.5-12 micron spectra of Normal Galaxies

M. Hur and N. Lu

Infrared Processing and Analysis Center MC 100-22
California Institute of Technology
Pasadena, CA 91125. USA

Introduction

ISOPHOT (PHT) was the imaging photo-polarimeter on-board the Infrared Space Observatory ISO.  The PHT-S was one of three subsystems which consisted of a dual grating spectrometer with resolving power of order 90 in two wavelength bands. Band SS covered the wavelength range 2.5-4.8 um and band SL covered the range 5.8-11.8 um. Each spectrometer used a linear array of 64 element Si:Ga, and PHT-S had one square entrance aperture with dimensions 24" x 24".

The resolution was about 85 for PHT-SS and about 95 for PHT-SL, respectively. The spectra could be fully sampled at half of the resolution, i.e. with 0.089 um (PHT-SS) and 0.1898 um (PHT-SL). PHT-S could be used with the chopper.  These and more detailed information can be found in ISO Handbook, Volume V: PHT--The Imaging Photo-Polarimeter (15/Feb/2000)

Sample Selection

All the data was retrieved using the ISO Archive.  There are total of 1509 entries for P40 (PHT-S), and all of these measurements RA and Dec were searched in the NED to find all galaxy observations.  After several iterations of elimination, 87 normal galaxies were hand selected. These are relatively nearby galaxies without signs of being in strong galaxy interaction.  In the end, there were at least several galaxies per each morphology group.

General Data Reduction

Most of the data reduction took place during the second half of the year 1999 using PIA (versions 7.3.2 and 8.1) with deglitching by hand as noted in the log files.  The data was obtained using the ISO Archive; (OLP system versions OLP_701 and OLP_70).

The steps noted in the P40 data reduction recipe given below were followed. Specific information and special reduction steps for each measurement were recorded in individual log files as shown at the end of this report.

Each spectrum represents the integrated flux within a 24"x24" aperture centered on a galaxy.

Data Presentation

The data are tables of values which consist on five columns for Wavelength in um, F(lambda) and its uncertainty in W/m^2/um, and Flux Density and its uncertainty in Jy. The atlas contains the 6 groups of normal galaxies as shown below. Each page of the atlas contains a postcard showing the spectra of the galaxies and their properties such as TDT number, RA, Dec, morphology type, optical magnitude, optical size (a*b), heliocentric velocity, and IRAS fluxes.

Supporting references are: Lu & Hur 2000, AAS, 196, 2702 and Lu et al. 2003, ApJ 588, 199.


Processing P40 data with PIA - staring or chopping mode

(PIA 7.3.2, March 1999)


This is a step-by-step guide illustrating how to reduce a P40 data (staring or chopping mode) from ERD to AAP (equivalent to the AAR, Auto Analysis Result, from the pipeline) with the PIA.  The default PIA parameter setting and default flux calibration table are used.  If you need more details, please refer to the PIA manual and the IDUM, ISOPHOT Data Users Manual, or contact ISO helpdesk at IPAC.

Select and read Data

Make sure the PIA paths are set up correctly.
    [ ]  (Top Window) Customize  ->  PIA paths

Select the P40 ERD file and read it into the PIA buffer.  The P40 ERD files have PSER prefix (both PHT-SS and SL measurements are together in one file).
    [ ]  (Top Window) Files  ->  Files Manager
    [ ]  Select File Type: ERD and Detectors: SS/SL using the two filter windows.
    [ ]  The P40 ERD file name(s) should appear in the "Files" subwindow.  If not,
         you can click on one of the subdirectory names shown in the
         "Subdirectories" subwindow to see if you can navigate to the desired file.
         Once you have located the correct file in the "Files" subwindow, click on
         the file name.
    [ ]  Click on "Read File" button to read the selected file into the PIA buffer.
    [ ]  Option: Click on "Show Header" button to view or to print the ERD FITS
         header.

Select an ERD measurement for processing.
    [ ]  (Top Window) Buffers  ->  Buffers Manager
    [ ]  Select Data Type: ERD and Detectors: SL/SS.  All the measurements in the
         selected category should show up in the "measurement" window.  Usually,
         there are 2 measurements: the first one is a "pseudo" dark measurement
         and the 2nd one is the real observation.  Hence, click on the 2nd
         measurement.
    [ ]  Click on the "Plot & Reduce Data" button to bring up the PIA ERD window.
    [ ]  Option: Click on the "Show..." button in the Buffers Manager window to
         view FITS header, Compact Status or even the data values themselves.

Reduction of the ERD (to SRD)

The PIA ERD window shows the read-out ramps as a function of time for 4 out of the 128 detector pixels.  Some readouts are masked out (shown as red x's) by default.
    [ ]  Option: Use the "Zoom & Print" button to blow up the displayed pixel in
         order to see individual ramps more clearly or to print the display on the
         laser printer.  This option is available on all reduction levels.
    [ ]  Option: Use the "Selection" button to change the read-out discarding
         scheme from the default.
    [ ]  (ERD Window) Correction  ->  Read-out simple deglitching
         (Non-linearity correction is not available for PHT-S at this time, but it
         is small.)
    [ ]  (ERD Window) Correction  ->  2 Threshold deglitching
    [ ]  (ERD Window) Process Meas.  ->  Fit Ramps (1st order polynomial)
         This fits a slope to each integration ramp and brings up the SRD window.
         You also have the option of dividing the ramp into a desired number of
         subdivided ramps using the fourth choice of the Process Meas.

Reduction of the SRD (to SCP)

The PIA SRD window displays the time series of the ramp slopes for 4 out of the 128 detector pixels.  Again, the masked out slopes by default are shown in red color.
    [ ]  (SRD Window) Correction  ->  Reset interval correction
    [ ]  (SRD Window) Correction  ->  Deglitching
         This is to filter out badly deviated slopes.
    [ ]  (SRD Window) Correction  ->  Dark Current Subtraction
         This is to subtract out the default orbital position dependent dark
         current.
    [ ]  Option: (SRD Window) Selection -> Discard Signals
         Use this to change the discarding scheme from the default.  If changes
         are made, do apply the deglitching correction again.
    [ ]  Option: (SRD Window) Data -> Save (to PIA internal file)
         This is to save the SRD result into a disk file.
    [ ]  (SRD Window) Process  ->  no drift handling (Option: with drift handling)
         This will bring up the SCP window.

Reduction of the SCP (to AAP)

The PIA SCP window shows the average slopes per chopper plateau as a function of time.   This data reduction step depends on whether your observation is chopped or staring.

In the case of a chopped observation:

    [ ]  (SCP Window) Process  ->  Background Subtraction (within measurement)
         This brings up two windows: PIA Background Subtraction Menu and a graphic
         window displaying the "grand average signal" per chopper step.
    [ ]  Usually, one needs only to click on the "OK" button in the Menu window.
    [ ]  Click on the "Subtracted meas -> buffer" button to write the
         sky-subtracted spectrum to the SCP buffer.
    [ ]  Now let's display the sky-subtracted spectrum. Exit out of all the Data
         Display windows, then go to the Buffer Control Panel and select SCP and
         SL/SS for the Data Type and Detectors respectively.  Select the
         background subtracted data and click on the "Plot & Reduce Data" button
         to bring up the PIA SCP window.
         Caution: avoid using the Load button to display the subtracted data
         because this makes the appropriate Process option (Chopped SPRF)
         unavailable.
    [ ]  (SCP Window) Process -> Power Calibration --> Chopped SPRF (only for SL)
         This will bring up the AAP window.
    [ ]  Option: you can save the SCP result of sky-subtracted spectrum by clicking
         in the SCP window "Data --> Save --> To a PIA Internal File."

In the case of a staring observation:

    [ ]  (SCP Window) Process -> Power Calibration --> Default Responses (orbital
         dep.) --> Perform it. This will bring up the AAP window.
    [ ]  Option: you can save the SCP result of sky-subtracted spectrum by clicking
         in the SCP window "Data --> Save --> To a PIA Internal File."

    Hint: if you have a sky measurement from another observation, you can do a
    sky subtraction from the spectrum of the current staring observation at
    the AAP level by click there "Process --> Background Subtraction --> another
    measurement." Make sure that you loaded the AAP result of the sky measurement.

Note: This data reduction of SCP to AAP actually produces the intermediate SPD result which is not displayed automatically. You can however display the SPD result using the buffer manager in the conventional way.

Examine the AAP result with Astrophysical Applications

The AAP (Astrophysical Applications product) result is comparable to the pipeline AAR (Automatic Analysis Result data).  The AAP result  is displayed in two windows, one for the SS part (2.5 to 5 microns) and one for the SL part (6 to 11.6microns) of the spectrum.   These spectra can be best examined using  "Astrophysical Work" available in the PIA top window.

    [ ]  Option: If you have not save the SPD result, you may want to save the
         AAP result now.  To do so, click "Data --> Save --> PIA Internal File"
         in each of the AAP windows displayed.
    [ ]  (Top Window) Buffers  ->  Astrophysical Work
         An Astrophysical Applications Menu window appears on your screen.
    [ ]  Select the "Spectro-Photometry" function.
         This brings up a window called PIA Spectro-photometry.
    [ ]  (Spectro-photometry window) Click on the "File" button and then
         "Select measurement."  Choose the measurement to be loaded.
    [ ]  (Spectro-photometry window) Click on the "Plot" button to plot the
         spectrum in a number of different ways.  Use the "new" option for
         the spectrum plot.

    Hint: To display the SS and SL parts of the spectrum together, first plot
    one as described above and leave the plot on. Then read the other part into
    Astrophysical Work, but choose "Overplot --> Synchronized" (instead of "New")
    to display the two parts together.

Data Reduction Log for Normal Galaxy Observations


NGC 5253 (09000876)

MESSIER 083  (09001367)

NGC 6000  (10201252)

NGC 6215  (10800963)

ESO 272- G 023  (10801350)

NGC 5915  (10802256)

NGC 6156  (10903051)

NGC 3705  (18400677)

IC 3600  (18401960)

NGC 3683  (19401040)

NGC 4194  (19401376)

NGC 3583  (19500259)

NGC 3949  (19500332)

NGC 4102  (19500586)

IC 1459  (20001975)

NGC 4490  (20501580)

NGC 6286  (20700516)

IC 0883  (21501377)

NGC 3379  (22201025)

NGC 4365  (22802240)

NGC 4691  (23101069)

NGC 4374  (23502642)

NGC 4621  (23502755)

NGC 4519  (23600331)

NGC 4418  (24100408)

NGC 4027  (24200368)

ESO 317- G 023  (25200171)

NGC 3250  (25200622)

NGC 3885  (25200727)

IC 3908  (25202254)

NGC 5866  (26902854)

NGC 3620  (27600983)

IC 4595  (27601375)

NGC 5962  (27800783)

NGC 1266  (28302701)

NGC 5713  (28400959)

NGC 5786  (29900767)

NGC 6753  (29901232)

NGC 7592  (36500795)

NGC 7218  (36902415)

NGC 7418  (36902723)

IC 5325  (36902824)

NGC 7552  (36903288)

NGC 7591  (38200567)

MRK 0789  (39600513)

NGC 5653  (40201037)

CGCG 049-057  (41801043)

UGC 12914  (43200817)

UGC 12915  (43200818)

NGC 0891  (43602845)

NGC 0023  (43801001)

UGC 02369  (46501643)

NGC 5430  (51400313)

NGC 7715  (55501402)

NGC 7714  (55501701)

NGC 4670  (56400857)

NGC 7771  (56500779)

NGC 5433  (57100315)

NGC 5258  (58300928)

NGC 0232  (59301307)

NGC 0693  (59502319)

NGC 0278  (59702263)

NGC 0828  (60202547)

IC 0860  (61800104)

UGC 02855  (62902698)

NGC 0695  (63300751)

UGC 02238  (63301036)

NGC 1741 NED03  (68801908)

NGC 6753  (68900230)

NGC 1546  (68900662)

IC 0342  (69802398)

IRAS 19420+4556  (70000997)

NGC 2415  (71704078)

NGC 1317  (75001077)

NGC 1326  (75001158)

NGC 0701  (76301124)

NGC 1125  (78000838)

NGC 1022  (78401024)

NGC 1385  (79600846)

NGC 1482  (79600986)

NGC 0838  (80600208)

UGC 02982  (80901443)

NGC 1377  (81201754)

IRAS 02530+0211  (82101050)

NGC 1222  (82400843)

UGCA 073  (82400989)

NGC 6946  (84001892)