---
title: GLADE V2 Galaxy Catalogue
url: https://www.emergentmind.com/topics/glade-v2-galaxy-catalogue
type: topic
---

# GLADE V2 Galaxy Catalogue

The GLADE V2 Galaxy Catalogue (GLADE⁺) is a homogenized, nearly all-sky catalogue designed for multimessenger astronomy, particularly for targeted follow-up of gravitational-wave detections. GLADE⁺ compiles data from six major astronomical surveys, providing astrometric, photometric, redshift, stellar mass, and compact binary merger-rate information for over 22 million galaxies and approximately 750,000 quasars. Incorporating Bayesian corrections for peculiar velocities, standardized magnitudes across multiple bands, and astrophysical priors such as stellar mass and B-band luminosity, it delivers high completeness out to luminosity distances critical for gravitational-wave counterpart searches [2110.06184].

## 1. Catalogue Construction and Data Sources

GLADE⁺ is assembled by merging six large-scale astronomical catalogues, each offering distinctive contributions in terms of depth, wavelength coverage, or sky coverage:

- **GWGC** (Gravitational Wave Galaxy Catalogue)
- **2MPZ** (2MASS Photometric Redshift)
- **2MASS XSC** (Extended Source Catalogue)
- **HyperLEDA**
- **WISExSCOSPZ** (WISE×SuperCOSMOS Photometric Redshifts): ~20 million galaxies with W1, W2 mid-infrared photometry, SuperCOSMOS B_J and R_F optical magnitudes, and neural network photometric redshifts (σₙₙₙₙₙₙₙₙ/(1+z) ≃ 0.033)
- **SDSS-DR16Q**: ~750,000 spectroscopically confirmed quasars, replacing the earlier DR12Q sub-sample

Integration proceeds by spatial cross-matching with 2″ radius for WISExSCOSPZ/GLADE v2.4, and AllWISE data (3″) to fill W1, W2 gaps. Unmatched W1 are approximated using K_s→W1 color-redshift relations from 2MPZ. After all steps, the combined catalogue includes 22,431,348 galaxies and 750,410 quasars, for a total of 23,181,758 objects. More than 21 million galaxies carry W1 photometry, enabling further astrophysical parameter estimates.

## 2. Redshift Corrections with Bayesian Origin Reconstruction

Observed galaxy redshifts at low redshift ($z \lesssim 0.05$) are contaminated by peculiar velocities, $v_p$, due to local structure. GLADE⁺ compensates these using the BORG (Bayesian Origin Reconstruction from Galaxies) formalism. The method samples the posterior 
$$
p(\delta, \theta | \{ z_i, x_i \}) \propto p(\{ z_i \} | \delta, \theta) \, p(\delta) \, p(\theta),
$$
where $\delta$ is the 3D density field and $\theta$ encodes bias/evolution. For each posterior sample, a velocity field $v(x)$ is obtained through Lagrangian particle-mesh combined with the Simplex-in-Cell estimator, yielding a posterior for each galaxy’s radial peculiar velocity $p(v_{p,i}|\text{data})$. The catalogue records both mean and standard deviation of $v_p$ per object; these uncertainties propagate to errors in the CMB-frame redshift $z_{\rm CMB}$.

A small-scale virial component is added in quadrature, with the one-dimensional dispersion for halo of mass $M_h$ given by
$$
\sigma_{\rm vir} = 476\,g_v [\Delta_{\rm nl}(z) E(z)^2]^{1/6} \left( \frac{M_h}{10^{15} M_\odot/h} \right)^{1/3} ~[\mathrm{km/s}]
$$
where $g_v = 0.9$, $\Delta_{\rm nl}(z) = 18\pi^2 + 60x - 32x^2$, $x = \Omega_m(1+z)^3/E(z)^2 - 1$, and $E(z) = H(z)/H_0$. Halo masses are estimated from $B$-band luminosity $L_B$ via:
$$
L_B = A (M_h/M_r)^b / [c + (M_h/M_r)^{dk}]^{1/k}
$$
with $A = 5.7 \times 10^9\,L_\odot$, $M_r = 10^{11}\,M_\odot$, $b=4$, $c=0.57$, $d=3.72$, $k=0.23$. The total velocity error is:
$$
\sigma_{\rm tot}^2 = \sigma_{\rm BORG}^2 + \sigma_{\rm vir}^2
$$
This approach yields CMB-frame redshifts corrected for local structure, crucial for accurate distance estimates in the nearby Universe.

## 3. Completeness Assessment

GLADE⁺ completeness is quantified by cumulative B-band luminosity and inclusion of the most luminous galaxies, relevant for host targeting.

- **Cumulative B-band luminosity**: Comparing observed $L_B$ within a sphere of given luminosity distance $d_L$ to expected total from the cosmic luminosity density $\rho_L=1.98\times10^{-2} (10^{10}L_{B,\odot})~{\rm Mpc}^{-3}$, 100% completeness is achieved at
  $d_L = 47^{+4}_{-2}$ Mpc.
- **Bright-galaxy completeness**: Galaxies contributing the top 90% of total $B$- or $K$-band luminosity are included out to $d_L \simeq 130$ Mpc.

| Completeness Metric      | Distance Scale (Mpc) | Details                                         |
|-------------------------|---------------------|-------------------------------------------------|
| 100% $L_B$ (all galaxies) | $47^{+4}_{-2}$       | Total expected B-band luminosity covered         |
| 90% $L_B$, $K$-band      | $\simeq 130$         | Brightest galaxies within the luminosity budget  |

This level of completeness is essential for connecting galaxy populations with gravitational-wave event localizations out to relevant distances.

## 4. Stellar Mass and Compact Binary Merger Rate Estimates

WISE W1 mid-infrared photometry allows GLADE⁺ to estimate stellar masses ($M_\star$) and galaxy-specific BNS merger rates.

- **Stellar mass estimation**: Galaxies are "passive" if $W2-W3 \leq 1.5$, otherwise "active." Adopted mass-to-light ratios (from Kettlety et al.) are:
  $$
  M_\star/L_{W1} = 0.65 \pm 0.07\ \text{(passive)},\qquad \log_{10}(M_\star/L_{W1}) = -0.4 \pm 0.2\ \text{(active)}
  $$
  with 
  $$
  L_{W1} = 10^{-0.4\,[M_{W1} - M_{\odot, W1}]},\quad M_{\odot, W1}=3.24\ \text{mag}
  $$
  $$
  M_{W1} = m_{W1} + 5 - 5\log_{10}(d_L/{\rm pc}) - K(z),\quad K(z) = -7.1\log_{10}(1+z)
  $$
  Only galaxies with $M_\star \geq 10^5\,M_\odot$ are retained ($\sim97\%$ completeness).

- **Binary neutron star (BNS) merger rates**:
  For $z \leq 0.1$ and $M_\star > 10^7\,M_\odot$, the rate (from Artale et al.) is:
  $$
  \log_{10}\left( N_{\rm BNS}/{\rm Gyr} \right) = 1.15\,\log_{10}(M_\star/M_\odot) - 7.22
  $$
  Rates (with uncertainties) are provided for 3.16 million galaxies.

| Parameter           | Estimate Method         | Coverage/Completeness                  |
|---------------------|------------------------|----------------------------------------|
| Stellar Mass ($M_\star$) | WISE W1 mass-to-light ratio | $M_\star \geq 10^5\,M_\odot$, $\sim$97%|
| BNS rate            | Artale et al. scaling  | For $z \leq 0.1$, $M_\star > 10^7\,M_\odot$ |

Uncertainties on stellar mass are typically in the range 30–70%, depending on galaxy type.

## 5. Ranking and Identification in Gravitational-Wave Follow-Up

GLADE⁺ enables optimized prioritization of host-galaxy candidates for gravitational-wave counterpart searches by associating astrophysical priors with localization volumes. For each candidate, a generic ranking statistic can be constructed:
$$
P_{\rm host} \propto p_{\rm GW}(\alpha, \delta, d_L) \times w_{\rm gal}
$$
where $p_{\rm GW}$ is LIGO/Virgo sky localization probability and $w_{\rm gal}$ is an astrophysical weighting, e.g., proportional to $L_B$, $M_\star$, or $N_{\rm BNS}$. This ranking allows observers to select the most probable galaxies to observe first. Empirical and simulation results indicate that this approach enables recovery of 50–90% of total host probability with substantially fewer telescope pointings than tiling, thus reducing required integration times and increasing rapid counterpart identification probability.

## 6. Catalogue Content and Distribution

GLADE⁺ provides a unified set of parameters for >22 million galaxies and ~750,000 quasars:

- Coordinates (RA, Dec)
- Redshifts (corrected for peculiar motion, plus errors)
- Magnitudes: $B, J, H, K_s, W1, W2$
- Stellar masses $M_\star$
- Binary neutron star merger rates $N_{\rm BNS}$
- Posterior means and variances of peculiar velocities

This homogenization and broad parameter space make it a powerful resource for multimessenger observational campaigns, especially for gravitational-wave counterpart searches in volumes probed by advanced interferometer networks [2110.06184].

Source: https://www.emergentmind.com/topics/glade-v2-galaxy-catalogue