Outer Halos of Early-Type Galaxies and Intracluster Light

Galaxies in a hierarchical universe are growing through accreting smaller systems. We study particularly the outer halos of massive galaxies to find signatures of this process, but also to characterize the kinematics, angular momentum, and dark matter in these halos, and to determine how they blend into their surroundings, the intracluster or intragroup light. We also host the website of the Planetary Nebula Spectrograph (PN.S) project; planetary nebulae are some of the best tracers to study the outermost regions of galaxies which are too faint for conventional spectroscopy.

Main topics

The Photometric and Kinematic Diversity of Galaxies at Large Radii

Stellar Halos: Accretion, Merger History, and Dark Halo Connection

The extended PN.S Early-Type galaxy project: Probing halo kinematics with Planetary Nebulae

The ePN.S early-type galaxy survey: Probing stellar halo transition Scale

Stellar populations and accretion in the outermost halos of bright cluster galaxies

Intracluster light

Dark matter in elliptical galaxies

Planetary nebulae in Andromeda (M31): Imaging the disk and halo

Key publications

Bhattacharya, S., Arnaboldi, M., Caldwell, N., Gerhard, O., Kobayashi, C., Hartke, J., Freeman, K. C., McConnachie, A. W., Guhathakurta, P., arXiv:2203.06428,
Radial oxygen and argon abundance gradients of the thin and thicker disc of Andromeda from planetary nebulae . 2022arXiv220306428

Hartke, J., Arnaboldi, M., Gerhard, O., Coccato, L., Merrifield, M., Kuijken, K., Pulsoni, C., Agnello, A., Bhattacharya, S., Spiniello, C., Cortesi, A., Freeman, K. C., Napolitano, N. R., Romanowsky, A. J., arXiv:2201.08710,
The halo of M105 and its group environment as traced by planetary nebula populations: II. Using kinematics of single stars to unveil the presence of intragroup light around the Leo I galaxies NGC 3384 and M105 . 2022arXiv220108710

Bhattacharya, S., Arnaboldi, M., Gerhard, O., McConnachie, A., Caldwell, N., Hartke, J., Freeman, K. C., 2021, A&A, 647,A130,
The survey of planetary nebulae in Andromeda (M 31). III. Constraints from deep planetary nebula luminosity functions on the origin of the inner halo substructures in M 31. 2021A&A...647A.130B

Pulsoni, C., Gerhard, O., Arnaboldi, M., Pillepich, A., Rodriguez-Gomez, V., Nelson, D., Hernquist, L., Springel, V., 2021, A&A, 647,A95,
The stellar halos of ETGs in the IllustrisTNG simulations. II. Accretion, merger history, and dark halo connection. 2021A&A...647A..95P

Hartke, J., Arnaboldi, M., Gerhard, O., Coccato, L., Pulsoni, C., Freeman, K. C., Merrifield, M., Cortesi, A., Kuijken, K., 2020, A&A, 642, A46,
The halo of M105 and its group environment as traced by planetary nebula populations. I. Wide-field photometric survey of planetary nebula in the Leo I group . 2020A&A...642A..46H

Pulsoni, C., Gerhard, O., Arnaboldi, M., Pillepich, A., Nelson, D., Hernquist, L., Springel, V., 2020, A&A, 641, A60
The Stellar Halos of ETGs in the IllustrisTNG Simulations; The photometric and kinematic diversity of galaxies at large radii . 2020A&A...641A..60P

Bhattacharya, S., Arnaboldi, M., Caldwell, N., Gerhard, O., Blaña Díaz, M., McConnachie, A., et al., 2019, A&A, 631, A56
The survey of planetary nebulae in Andromeda (M 31). II. Age-velocity dispersion relation in the disc from planetary nebulae. 2019A&A...631A..56B

Bhattacharya, S., Arnaboldi, M., Hartke, J., Gerhard, O., Comte, V., McConnachie, A., et al., 2019, A&A, 624, A132
The survey of planetary nebulae in Andromeda (M 31). I. Imaging the disc and halo with MegaCam at the CFHT. 2019A&A...624...A132

Longobardi, A., Arnaboldi, M., Gerhard, O., Pulsoni, C., Söldner-Rembold, I., 2018, A&A, 620, A111,
Kinematics of the outer halo of M 87 as mapped by planetary nebulae. 2018A&A...620A.111L

Pulsoni, C., Gerhard, O., Arnaboldi, M., Coccato, L., Longobardi, A., Napolitano, N. R., et al., 2018, A&A, 618, A94,
The extended Planetary Nebula Spectrograph (ePN.S) early-type galaxy survey: The kinematic diversity of stellar halos and the relation between halo transition scale and stellar mass. 2018A&A...618A..94P

Hartke, J., Arnaboldi, M., Gerhard, O., Agnello, A., Longobardi, A., Coccato, L., et al. 2018, A&A, 616, A123.
Three dynamically distinct stellar populations in the halo of M49. 2018A&A..616..A123

Hartke, J., Arnaboldi, M., Longobardi, A., Gerhard, O., Freeman, K. C., Okamura, S., et al., 2017, A&A, 603, A104,
The halo of M 49 and its environment as traced by planetary nebulae populations. 2017A&A..603..A104

Longobardi, A., Arnaboldi, M., Gerhard, O., Mihos, J. C., 2015, A&A, 579, L3,
The build-up of the cD halo of M 87: evidence for accretion in the last Gyr. 2015A&A...579L...3L

Longobardi, A., Arnaboldi, M., Gerhard, O., Hanuschik, R., 2015, A&A, 579, A135,
The outer regions of the giant Virgo galaxy M 87 Kinematic separation of stellar halo and intracluster light. 2015A&A...579A.135L

Morganti, L., Gerhard, O., Coccato, L., Martinez-Valpuesta, I., Arnaboldi, M., 2013, MNRAS, 431, 3570,
Elliptical galaxies with rapidly decreasing velocity dispersion profiles: NMAGIC models and dark halo parameter estimates for NGC 4494. 2013MNRAS.431.3570M

Arnaboldi, M., Ventimiglia, G., Iodice, E., Gerhard, O., Coccato, L., 2012, A&A, 545, A37,
A tale of two tails and an off-centered envelope: diffuse light around the cD galaxy NGC 3311 in the Hydra I cluster. 2012A&A...545A..37A

de Lorenzi, F., Gerhard, O., Coccato, L., Arnaboldi, M., Capaccioli, M., Douglas, N. G., et al., 2009, MNRAS, 395, 76,
Dearth of dark matter or massive dark halo? Mass-shape-anisotropy degeneracies revealed by NMAGIC dynamical models of the elliptical galaxy NGC
3379. 2009MNRAS.395...76D

Coccato, L., Gerhard, O., Arnaboldi, M., Das, P., Douglas, N. G., Kuijken, K., et al., 2009, MNRAS, 394, 1249,
Kinematic properties of early-type galaxy haloes using planetary nebulae. 2009MNRAS.394.1249C

de Lorenzi, F., Gerhard, O., Saglia, R. P., Sambhus, N., Debattista, V. P., Pannella, M., et al., 2008, MNRAS, 385, 1729,
Dark matter content and internal dynamics of NGC 4697: NMAGIC particle models from slit data and planetary nebula velocities. 2008MNRAS.385.1729D