# A Physical Properties Catalog for Low-redshift Galaxies from DESI Legacy Imaging Surveys DR10

## Overview

This dataset provides a catalog of galaxy physical properties for the DESI Legacy Imaging Surveys Data Release 10 (LS DR10).  
It contains estimates of star formation rate (SFR), stellar mass, and gas-phase oxygen abundance for approximately **547 million low-redshift galaxies (z ≤ 0.5)**.

The physical properties are derived using a **multimodal deep learning approach** that jointly incorporates optical imaging data and photometric catalog features.  

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## Data Contents

### 1. Galaxy Physical Properties Catalogs

The main physical properties catalogs are split into **360 CSV files**:

```
tractor-gal-000.csv
tractor-gal-001.csv
...
tractor-gal-359.csv

```

Each file corresponds to a subset of DESI LS DR10 galaxies and contains:
- Galaxy coordinates and identifiers
- Redshift information
- Estimated physical properties (SFR, stellar mass, metallicity)
- Quality flags related to photometry and image cutouts

#### Column Description 

Below is a description of the columns included in each `tractor-gal-XXX.csv` file.

| Name | Format | Unit | Description |
|-----|--------|------|-------------|
| desiid | string | -- | Unique DESI LS target identifier, constructed from `release-brickid-objid`. |
| RA | float | deg | Right ascension. |
| DEC | float | deg | Declination. |
| z_spec | float | -- | Spectroscopic redshift collected from multiple spectroscopic surveys. |
| z_phot | float | -- | Photometric redshift from Li et al. (2024). |
| maskbits | int | -- | LS photometric quality flag; `maskbits = 0` indicates uncontaminated photometry. |
| MAG_R | float | mag | r-band model magnitude from DESI LS DR10. |
| log(SFR) | float | log(M☉ yr⁻¹) | Logarithm of the star formation rate. |
| log(M*) | float | log(M☉) | Logarithm of the stellar mass. |
| 12+log(O/H) | float | -- | Gas-phase oxygen abundance. |
| Cat_FLAG | 8-bit int | -- | Photometric completeness flag across bands (1: valid; 0: filled value). |
| Image_FLAG | 4-bit int | -- | Image availability flag (1: complete cutout; 0: missing image; 2: incomplete cutout). |
| Image_Padded | float | -- | Fraction of padded pixels in the image cutout (0: no padding; 0 < value ≤ 1: partially padded; NaN: missing image). |

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### 2. Photometric Feature Files

In addition to the physical properties catalogs, **three auxiliary files** are provided.  
These files contain the **photometric features used as model inputs** for estimating each physical property:

- SFR_features.txt: **28** photometric features for **SFR estimation**
- stellar_mass_features.txt: **50** photometric features for **stellar mass estimation**
- oxygen_abundance_features.txt: **1626** photometric features for **metallicity estimation**

These features are constructed from DESI LS DR10 model magnitudes, aperture magnitudes, and their combinations (colors and aperture differences), and are provided for reference.

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