---
license: cc-by-4.0
task_categories:
- other
language:
- en
tags:
- astronomy
- spectroscopy
- galaxies
- desi
- cosmology
size_categories:
- n<1K
---

# DESI DR1 ELG Galaxy Spectra Dataset

This dataset contains 999 Emission Line Galaxy (ELG) spectra from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1, along with associated metadata. This is a curated sample of high-quality galaxy spectra suitable for research and educational purposes in astronomy and cosmology.

## Dataset Summary

- **Total galaxies**: 999 Emission Line Galaxies (ELGs)
- **Data source**: DESI Data Release 1 
- **Redshift range**: 0.600 - 0.948
- **Spectral coverage**: 3600 - 9824 Å (7781 wavelength points per spectrum)
- **Survey**: DESI Main Survey (dark time program)

## Dataset Structure

### Files

- `metadata.csv` - Galaxy properties and catalog information (999 galaxies + header)
- `spectrum_GALAXY_*.json` - Individual spectrum files (999 files)
- `README.md` - Detailed documentation and usage examples

### Metadata Columns

| Column | Description |
|--------|-------------|
| `targetid` | DESI target identifier |
| `galaxy_type` | Galaxy type classification (ELG) |
| `spectype` | Spectroscopic type (GALAXY) |
| `ra`, `dec` | Right ascension and declination (degrees) |
| `redshift` | Spectroscopic redshift |
| `z_bin` | Redshift bin (0.6-0.8, 0.8-1.0) |
| `survey` | DESI survey (main) |
| `program` | Observing program (dark) |
| `healpix` | HEALPix pixel ID |
| `desi_target`, `bgs_target`, `mws_target`, `scnd_target` | DESI targeting bitmasks |

### Spectrum File Format

Each spectrum file contains:
- **Metadata**: Object properties (redshift, coordinates, survey info)
- **Spectral data**: Wavelength array, observed flux, model fit, and inverse variance

## Usage

```python
import pandas as pd
import json
import numpy as np

# Load metadata
metadata = pd.read_csv('metadata.csv')
print(f"Dataset contains {len(metadata)} ELG galaxies")

# Load a spectrum
with open('spectrum_GALAXY_0.6004_7006c68c_20250811_152534.json', 'r') as f:
    spectrum = json.load(f)

wavelength = np.array(spectrum['data']['wavelength'])
flux = np.array(spectrum['data']['flux'])
redshift = spectrum['metadata']['redshift']
```

## Data Source and Citation

This dataset is derived from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1. 

**DESI Collaboration**: Please cite the appropriate DESI DR1 papers when using this dataset:
- DESI Collaboration et al. (2024). "The Dark Energy Spectroscopic Instrument (DESI) Data Release 1"

## License

This dataset is released under the Creative Commons Attribution 4.0 International License (CC BY 4.0).

## Applications

This dataset is suitable for:
- Galaxy spectroscopy research
- Redshift analysis and cosmology studies
- Machine learning applications in astronomy
- Educational purposes in astrophysics courses
- Spectral analysis method development

## Technical Details

- **Wavelength coverage**: 3600-9824 Å
- **Spectral resolution**: ~7781 points per spectrum
- **Flux units**: 10⁻¹⁷ erg/s/cm²/Å
- **File format**: JSON for spectra, CSV for metadata
- **Total size**: ~2.5 GB (including all spectrum files)