publications

 Kleiner, Serra, Loni et al. (2025), A&A, in press

The amazing sensitivity of our MeerKAT data allowed us to study the HI mass function of galaxies in Fornax down to 1 million solar masses of HI. We detected for the first time a strong departure of the HI mass function from the standard low-mass power law. The image on the left shows that the HI mass function collapses -- the number of galaxies is 5-10 times smaller than expected -- for HI masses below 10 million solar masses. This is the first time such an HI mass function collapse is observed. We interpret it as a result of the fast removal of HI from low-mass galaxies in Fornax.

Kamphuis, Serra, Kleiner et al. (2025), A&A, 696, A138

The late-type dwarf galaxy ESO 358-60 is the only Fornax member where we detect a settled HI disc much larger than the stellar body. The lack of any signs of interaction with the cluster environment even in the outer HI disc of such a small galaxy made us suspect that ESO 358-60 is actually outside Fornax. In this paper we confirm this hypothesis through a detailed study of the HI kinematics, which allows us to place the galaxy on the baryonic Tully-Fisher and thus measure its redshift-independent distance. We find that ESO 358-60 is almost exactly half-way between us and Fornax and, indeed, well outside the cluster.

Loi, Serra, Murgia et al. (2025), A&A, 694, A125

This paper presents the initial results obtained from broadband spectro-polarimetry data between 900 MHz and 1.4 GHz. We successfully detected a large number of polarized sources (~80 sources/deg²), providing the first indications of their cosmological evolution. The analysis of the polarized signals enabled us to reconstruct the rotation measure (RM) grid, which serves as a tracer of the intracluster magnetic field. For the first time, we identified peculiar features in the RM grid, including a stripe of high RM values extending from north to south through the cluster center and an increase in the RM radial profile at approximately 300 kpc. These RM characteristics can potentially be explained by a combination of cluster physics and the large-scale structure filaments surrounding the Fornax cluster.

Zabel, Loni, Sarzi et al. (2024), MNRAS, 535, 2538

This paper presents a detailed analysis of the atomic, molecular, and ionised gas in six dwarf galaxies in the Fornax cluster. The interstellar medium of these dwarfs is highly disturbed, and the three gas phases are often decoupled both spatially and in velocity. The observed gas distributions and velocity fields are not consistent with ram pressure stripping alone. In line with with previous studies, this indicates that other mechanisms, such as mergers, tidal stripping and other forms of pre-processing, play a role.

Serra, Oosterloo, Kamphuis et al. (2024), A&A, 690, A4

A detailed analysis of the distribution and kinematics of HI in the LMC-like Fornax galaxy NGC 1427A. The properties of the long HI tail and the peculiar kinematics of HI in the outer region of the stellar body are caused by ram pressure. However, several properties cannot be explained solely by ram pressure, such as: the close match between dense HI and stars within the disturbed stellar body; the abundant kinematically-anomalous HI; and the inversion of the HI velocity gradient near the base of the HI tail. We rule out an interaction with the cluster tidal field, and conclude that NGC 1427A is the result of a high-speed galaxy encounter or of a merger started at least 300 Myr ago, where ram pressure shapes the distribution and kinematics of the HI in the perturbed outer stellar body and in the tidal tails.

Loubser, Mosia, Serra et al. (2024), MNRAS, 527, 7158

The star formation history of galaxies in the Fornax A group reconstructed based on SALT optical spectroscopy. We find the pre-processing stage defined by Kleiner et al. (2021, see below) to be related to the recent specific star formation rate of galaxies in the group, in particular when measured in the outer regions of the stellar disc.

Kleiner, Serra, Maccagni et al. (2023), A&A, 675, A108

A study of the HI content of dwarf galaxies in the MeerKAT Fornax Survey covering 50% of the survey footprint.  We show that the few HI-detected dwarfs have as much HI as similar galaxies in the field, and reveal a population of strongly HI-deficient blue dwarfs, candidates for very recent HI removal. The sample properties imply the rapid removal of HI from dwarf galaxies in Fornax.

Loni, Serra, Sarzi et al. (2023), MNRAS, 523, 1140

A study of the outside-in transformation of the Fornax galaxy NGC 1436 from a spiral into a lenticular morphology. This galaxy hosts an inner, gas-rich, settled, star-forming disc and an outer, gas-poor, quiescent disc. Our deep HI data show no indications of recent interactions. Our stellar populations study reveals a starburst occurred ~ 5 Gyr ago, likely during the first infall of NGC 1436 into Fornax, followed by fast and slow quenching of the star formation activity in the outer and inner disc, respectively. This work is based on a combination of MeerKAT, ALMA and MUSE data, and includes a comparison to simulations.

Serra, Maccagni, Kleiner et al. (2023), A&A, 673, A146

This is the survey description paper, meant as a general reference for the survey, where we also present the first unambiguous evidence of ram pressure shaping the distribution of HI in the Fornax cluster: six galaxies with one-sided, star-less HI tails radially aligned within the cluster and with velocity gradients consistent with the direction of the ram-pressure wind given the galaxies' motion along the line of sight. The disturbed optical morphology of all host galaxies supports the idea that the tails consist of HI initially pulled out of the galaxies' stellar body by tidal forces. Ram pressure was then able to further displace the weakly bound HI and give the tails their present direction, length and velocity gradient. 

Loi, Serra, Murgia et al. (2022), A&A, 660, A48

First measurement of the magnetic field in an HI tidal tail formed during a galaxy merger. The tail is a remnant of the formation of NGC 1316 / Fornax A, and we could measure the magnetic field strength thanks to the tail's depolarizing effect on the western  radio lobe of Fornax A. This work is based on a combination of MeerKAT and ASKAP data.

Maccagni, Serra, Gaspari et al. (2021), A&A, 656, A45

A detailed study of the recurrent feeding/feedback cycle regulating the nuclear activity of Fornax A. This work is based on the analysis of the spatial distribution and kinematics of neutral atomic, molecular and ionised gas in Fornax A and combined observations from MeerKAT, MUSE and ALMA. The properties of the multi-phase interstellar medium are consistent with what is expected if the AGN activity is regulated by chaotic cold gas accretion.

Kleiner, Serra, Maccagni et al. (2021), A&A, 648, A32

Deepest HI image to date of the Fornax A group, showing diverse HI morphologies and plenty of HI clouds, tails and streams in the intra-group medium. We study the properties of galaxies in the group in the context of current ideas on pre-processing before in-fall into a cluster. We also show an extraordinarily extended, complex distribution of ionised gas in the intra-group medium, some of it associated with HI, which might be related to the recent AGN activity of NGC 1316 or to interactions within the group.

Maccagni, Murgia, Serra et al. (2020), A&A, 634, A9

A study of the SED of Fornax A from 80 MHz to 200 GHz, including new MeerKAT and SRT data, showing that its nuclear activity has been flickering during the last few tens of million years.

Serra, Maccagni, Kleiner et al. (2019), A&A, 628, A122

One of the first MeerKAT imaging papers, presenting the discovery of two long tails of hydrogen gas around NGC 1316 and discussing their implication for the merger history of this galaxy.

Serra et al. (2016), proceedings of MeerKAT Science: On the Pathway to the SKA, 25-27 May 2016, Stellenbosch, South Africa

Describes the survey science goals and design.

Chaturvedi, Tonnesen, Bryan et al. (2024), ApJ, 969, 28

Predictions on the presence of HI in the intra-cluster medium of Fornax-like galaxy clusters from the TNG50 cosmological simulations. According to the simulations, the typical covering fraction of HI outside galaxies is between a few and 10%, with significant cluster-to-cluster variations. Most of this intra-cluster HI seems to originate from galaxies based on its location and velocity.

Morokuma-Matsui, Bekki, Wang et al. (2022), ApJS, 263, 40

The most comprehensive study of the molecular gas content of Fornax galaxies to date, including a comparison with the atomic gas content as a function of stellar mass and star formation rate. It shows that the low star formation activity in Fornax results from a general lack of cold gas (primarily atomic, and to a less extent molecular) and not from a low star formation efficiency.

Loni, Serra, Kleiner et al. (2021), A&A, 648, A31

First interferometric blind HI survey of the Fornax cluster, revealing the diversity of HI morphologies of the gas-rich galaxies in the cluster and their likely transformation within and on their way to Fornax. We study the relation between HI properties, stellar mass, CO and star formation activity of these galaxies, and argue that HI removal proceeds faster than a cluster crossing time but at a sufficiently slow pace to keep the galaxies' star formation rate "in sync" with the overall HI content.

Zabel, Davis, Sarzi et al. (2020), MNRAS, 496, 2155

Spatially resolved star formation efficiency and molecular gas depletion time of galaxies in the Fornax cluster at 300 pc resolution.

Maddox, Serra, Venhola, Peletier, Loubser, Iodice (2019), MNRAS, 490, 1666

The most comprehensive compilation of spectroscopy to date, including published, unpublished and new observations, covering the Fornax area and background volume, providing redshifts for more than 1000 confirmed Fornax cluster objects (galaxies and GCs) and more than 6000 background galaxies.

Morokuma-Matsui, Serra, Maccagni et al. (2019), PASJ, 71, 85

Distribution and kinematics of CO within the stellar body of NGC 1316 at ~ kpc resolution.

Zabel, Davis, Smith et al. (2019), MNRAS, 483, 2251

Evidence of molecular gas stripping and deficiency in the Fornax cluster.

Lee-Waddell, Serra, Koribalski et al. (2018), MNRAS, 474, 1108

First result on Fornax from our data obtained with the ATCA telescope, showing that NGC 1427A is a remnant of a tidal interaction and not, as previously thought, a case of strong ram-pressure stripping.

Ramatsoku, Serra, Sun et al. (2025), A&A, 694, A159

ESO 137-1 is a quintessential jellyfish galaxy, and this paper presents its first ever HI detection and imaging. The galaxy has lost 90% of its original HI mass, and 2/3 of the surviving HI is found at larger distance from the stellar body than expected for a normal disc, forming a 40-kpc long HI tail largely coincident with the tail detected at other wavelengths.

Boselli, Serra, de Gasperin et al. (2023), A&A, 676, A92

Discovery of a tail of ram pressure-stripped HI and discussion on its origin in a galaxy in the Virgo cluster. This work is based on data from the new Virgo survey ViCTORIA.

Molnár, Serra, van der Hulst et al. (2022), A&A, 659, A94

We map the HI content in the inner ∼1 Mpc of the Coma cluster extending out to 1.5 Mpc towards the SW NGC 4839 group. We detect HI in 40 galaxies, of which 24 are new HI detections. We find that ∼75% of these galaxies have simultaneously enhanced SFR (by ∼0.2 dex) and are HI deficient (by ∼0.5 dex) compared to field galaxies. This could indicate either HI stripping of already highly star forming galaxies on a very short timescale, or to HI stripping coupled to a brief starburst phase triggered by ram pressure before eventually quenching the galaxy.

Müller, Poggianti, Pfrommer et al. (2020), Nature Astronomy, 5, 159

First ever measurement of the magnetic field strength and orientation in the gas disc and tail of a ram-pressure-stripped jellyfish galaxy.

Ramatsoku, Serra, Poggianti et al. (2020), A&A, 640, A22

Surprisingly similar effects of ram pressure stripping on two jellyfish galaxies living  in two extremely different clusters.

Ramatsoku, Serra, Poggianti et al. (2019), MNRAS, 487, 4580

Evidence of HI gas removal and enhanced star formation in the cluster jellyfish galaxy JO206, part of the GASP sample. Systems of this kind form a key comparison sample for the MeerKAT Fornax Survey.