Fixing HCO+ baseline fits for TP data

[eacmills]

A description of identification and classification of HCO+ baseline fitting issues in the TP data (SPW 21)

Identification: Baseline issues can be identified in plots from the HSD_Baseline task (usually task number 11)

The first set of plots from this task (Spectral Data Before Baseline Subtraction) show spatially-averaged spectra across the observed region, with a red line indicating the baseline that is being fit and subtracted. Cyan windows show the regions that are masked as line emission in each fit:

This plot is usually sufficient for diagnosis, but you can also compare it to the averaged pre-subtraction spectra (which show the overall line profile more clearly:

And the post-subtraction spectra:

Classification:

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General failure—

Line masking is incomplete and patchy, up to the point that entire HCO+ profiles are sometimes being included as ‘line-free” regions in baseline fits Example (#252):

Issues: #32 #121 #167 #169 #170 #173 #177 #180 #183 #187 #190 #193 #197 #217 #223 #227 #233 #236 #246 #252 #284

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Edge cases

Line emission goes to the edge of the SPW, and the baseline selection includes some line emission right at the edge of the band in the fitting, biasing the baseline Example (#175):

Issues: #166 #172 #175 #221 #226 #262 #271 #278 #285

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Weird baseline shapes—

Limited line-free regions and incomplete masking of line emission combine with high-order polynomial fitting to make wonky baseline fits that distort the resulting spectra. Example (#184):

Issues: #25 #29 #164 #172 #183 #184 #190 #221 #224 #229 #239

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(Nearly) acceptable fits--

Almost everything appears affected to some degree. These are just the least so Issues: #215 #219 #245

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Velocity shift--

Should check if these windows appropriately match velocity range of the 12m data, as substantial line emission is outside of the band Issues: #32 #36 #221

While HCO+ seems to be the most affected, HNCO (SPW) should probably also be carefully inspected once a uniform approach to fixing HCO+ has been decided on.

[snlongmore]

I have submitted a Helpdesk ticket (#21166) for this requesting QA3 to fix this and cc'd @keflavich and @ashleythomasbarnes.

[snlongmore]

@eacmills @keflavich @ashleythomasbarnes : I've had a request from ALMA -- could you please provide a list of affected MOUSs so they can open a PRTSPR ticket for the QA3 request. Thanks!

[ashleythomasbarnes]

@snlongmore my understanding is that this was present in every dataset - @eacmills could you confirm?

[eacmills]

Yes

On Wed, Feb 22, 2023 at 12:47 PM Ashley Barnes @.***> wrote:

@snlongmore https://github.com/snlongmore my understanding is that this was present in every dataset - @eacmills https://github.com/eacmills could you confirm?

— Reply to this email directly, view it on GitHub https://github.com/ACES-CMZ/reduction_ACES/issues/319#issuecomment-1440611256, or unsubscribe https://github.com/notifications/unsubscribe-auth/AQEUMJRGGR54622C6FQECDLWYZNNHANCNFSM6AAAAAAUY4GTG4 . You are receiving this because you were mentioned.Message ID: @.***>

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Dr. Elisabeth A.C. Mills (She/Her/Hers) Assistant Professor KU Physics & Astronomy Malott Hall 2058B

[snlongmore]

Thanks @ashleythomasbarnes and @eacmills. I have passed that information on to ALMA through the helpdesk.

[snlongmore]

https://jira.alma.cl/browse/PRTSPR-63088 for QA3 opening is created.