meeting 2025 12 17 gw - JacobPilawa/TriaxSchwarzschild_wiki_6 GitHub Wiki

Context

• Following up on some of the things we discussed in the meeting yesterday with the Vaderbilt folks. Mostly testing the alterate J23 approach to the mass estimation, as well as trying to track down what's going on with the "straggler" low stellar mass sources.
• I have some diagnositcs on the J23 (simple, L_W1) mass prescription, as well as tracking down the stragglers with low M*. Going to now to turn to comparing some individual sources that have dynamical Mbh to comapre the inferred values vs. true values.

Diagnostics

Simpler J23 Stellar Mass Prescription

• First, here's a quick comparison of the M* obtained from the "simple" J23 prescription which uses W1 luminosity alone, compared with the prescription which takes the W1-W2 color into account.

• For clarifying, here are the two most relevant expressions for calculating the masses:

• Getting the luminosity:

L(band)/L_\odot = 10^{-0.4(M(band) - M_\odot(band))}

• Getting M/L from the J23 prescription:

\log(M/L) = -0.030 - 1.960\,(W1 - W2)

• Getting stellar mass with L and M/L

M^{*} = L_{W1} \times \frac{M}{L_{W1}}

• Getting stellar mass from L alone:

\log_{10} M_\star = -12.62185 + 5.00155\,\log_{10}(L_{W1})
- 0.43857\,\left[\log_{10}(L_{W1})\right]^2
+ 0.01593\,\left[\log_{10}(L_{W1})\right]^3

• And if I apply these prescriptions to our data, I get the following:
  • I included a version where the y-axis is logged so you can better see the wings of the residual distribution.

One-to-One	Residuals	Residuals (log y scale)
[images/251218/one_to_one.png]]](/JacobPilawa/TriaxSchwarzschild_wiki_6/wiki/[[images/251218/residuals.png)	images/251218/residuals_log_scale.png

Tracking down the Low M* Tail of Sources

• We also have been curious about the low-lying tail of sources in this plot:

images/251218/stragglers.png

• I've tried a few different ways of visualizing the data so we can narrow down what these sources are. It seems like they're in large part some of the FAINTEST sources in the data (with M_{W1}>=-16 or so), and they are all preferentially W1-W2<0 (restframe) colors.

  • This is noteworthy because WSCOS cuts out W1-W2<0 from their data (though it seems they do these cuts in the observed frame and not the rest frame).

• The two most relevant plots showing this are here:

  • I think the Mass differences vs. Color plot is the most telling -- seems pretty clear that the majority of the low mass sources (and, in turn, the most discrepant from the K-band measurements), are located at or below W1-W2=0
  • The other plot confirms that we're looking at the faintest (absolute) sources. Going to look to see if the redshifts for these sources are particular.

Mass differences vs. Color	Mass differences vs. Absolute W1 Magnitude
[images/251218/plot1.png]]](/JacobPilawa/TriaxSchwarzschild_wiki_6/wiki/[[images/251218/plot2.png)

• Maybe a path forward is to first apply the same W1-W2<0 cut to the 2MPZ data and see how things are cleaned up. Alternatively, we can also do the cut in the rest-frame, but that probably requires us to look a bit into the general population of W1-W2 colors for the galaxies we expect in our sample.

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