Testing core creation in hydrodynamical simulations using the HI kinematics of field dwarfs

The majority of recent hydrodynamical simulations indicate the creation of central cores in the mass profiles of low-mass halos, a process that is attributed to star formation-related baryonic feedback. Core creation is regarded as one of the most promising solutions to potential issues faced by the lambda cold dark matter (LambdaCDM) cosmology on small scales. For example, the reduced dynamical mass enclosed by cores can explain the low rotational velocities measured for nearby dwarf galaxies, thus possibly lifting the seeming contradiction with the LambdaCDM expectations (the so-called "too big to fail" problem). Here we test core creation as a solution of cosmological issues by using a sample of dwarfs with measurements of their atomic hydrogen (HI) kinematics extending to large radii. Using the NIHAO hydrodynamical simulation as an example, we show that core creation can successfully reproduce the kinematics of dwarfs with small kinematic radii, R <~ 1.5 kpc. However, the agreement with observations becomes poor once galaxies with kinematic measurements extending beyond the core region, R ~ 1.5 - 4 kpc, are considered. This result illustrates the importance of testing the predictions of hydrodynamical simulations that are relevant for cosmology against a broad range of observational samples. We would like to stress that our result is valid only under the following set of assumptions: i) that our sample of dwarfs with HI kinematics is representative of the overall population of field dwarfs, ii) that there are no severe measurement biases in the observational parameters of our HI dwarfs (e.g., related to inclination estimates), and iii) that the HI velocity fields of dwarfs are regular enough to allow the recovery of the true enclosed dynamical mass.Comment: v2 matches version accepted by A&A. About 5 pages, 1 figur

The Multi-Wavelength Tully-Fisher relation with spatially resolved HI kinematics

In this paper we investigate the statistical properties of the Tully-Fisher relation for a sample of 32 galaxies with measured distances from the Cepheid period-luminosity relation and/or TRGB stars. We take advantage of panchromatic photometry in 12 bands (from FUV to 4.5 $\mu$m) and of spatially resolved HI kinematics. We use these data together with three kinematic measures ($W^{i}_{50}$, $V_{max}$ and $V_{flat}$) extracted from the global HI profiles or HI rotation curves, so as to construct 36 correlations allowing us to select the one with the least scatter. We introduce a tightness parameter $\sigma_{\perp}$ of the TFr, in order to obtain a slope-independent measure of the goodness of fit. We find that the tightest correlation occurs when we select the 3.6 $\mu$m photometric band together with the $V_{flat}$ parameter extracted from the HI rotation curve.Comment: 16 pages, 16 figures, accepted for publication in MNRAS, minor changes due to proof correction

A new astrophysical solution to the Too Big To Fail problem - Insights from the MoRIA simulations

We test whether advanced galaxy models and analysis techniques of simulations can alleviate the Too Big To Fail problem (TBTF) for late-type galaxies, which states that isolated dwarf galaxy kinematics imply that dwarfs live in lower-mass halos than is expected in a {\Lambda}CDM universe. Furthermore, we want to explain this apparent tension between theory and observations. To do this, we use the MoRIA suite of dwarf galaxy simulations to investigate whether observational effects are involved in TBTF for late-type field dwarf galaxies. To this end, we create synthetic radio data cubes of the simulated MoRIA galaxies and analyse their HI kinematics as if they were real, observed galaxies. We find that for low-mass galaxies, the circular velocity profile inferred from the HI kinematics often underestimates the true circular velocity profile, as derived directly from the enclosed mass. Fitting the HI kinematics of MoRIA dwarfs with a theoretical halo profile results in a systematic underestimate of the mass of their host halos. We attribute this effect to the fact that the interstellar medium of a low-mass late-type dwarf is continuously stirred by supernova explosions into a vertically puffed-up, turbulent state to the extent that the rotation velocity of the gas is simply no longer a good tracer of the underlying gravitational force field. If this holds true for real dwarf galaxies as well, it implies that they inhabit more massive dark matter halos than would be inferred from their kinematics, solving TBTF for late-type field dwarf galaxies.Comment: 21 pages, 21 figures. Accepted for publication in A&A. Corrected certain values in Table

EDGE -- Dark matter or astrophysics? Clear prospects to break dark matter heating degeneracies with HI rotation in faint dwarf galaxies

Low-mass dwarf galaxies are expected to showcase pristine `cuspy' inner dark matter density profiles compared to their stellar sizes, as they form too few stars to significantly drive dark matter heating through supernovae-driven outflows. Here, we study such simulated faint systems ($10^4 \leq M_{\star} \leq 2\times 10^6 \, M_\mathrm{\odot}$) drawn from high-resolution (3 pc) cosmological simulations from the `Engineering Dwarf Galaxies at the Edge of galaxy formation' (EDGE) project. We confirm that these objects have steep and rising inner dark matter density profiles at $z=0$, little affected by galaxy formation effects. But five dwarf galaxies from the suite showcase a detectable HI reservoir ($M_{\mathrm{HI}}\approx 10^{5}-10^{6} \, M_\mathrm{\odot}$), analogous to the observed population of faint, HI-bearing dwarf galaxies. These reservoirs exhibit episodes of ordered rotation, opening windows for rotation curve analysis. Within actively star-forming dwarfs, stellar feedback easily disrupts the tenuous HI discs ($v_{\phi} \approx 10\, \mathrm{km} \, \mathrm{s}^{-1}$), making rotation short-lived ($\ll 150 \, \mathrm{Myr}$) and more challenging to interpret for dark matter inferences. Contrastingly, we highlight a long-lived ($\geq 500 \, \mathrm{Myr}$) and easy-to-interpret HI rotation curve extending to $\approx 2\, r_{1/2, \text{3D}}$ in a quiescent dwarf, that has not formed new stars since $z=4$. This stable gas disc is supported by an oblate dark matter halo shape that drives high angular momentum gas flows. Our results strongly motivate further searches for HI rotation curves in the observed population of HI-bearing low-mass dwarfs, that provide a key regime to disentangle the respective roles of dark matter microphysics and galaxy formation effects in driving dark matter heating.Comment: Main text 10 pages, submitted to MNRAS. Comments welcome

Regulation der Genexpression von MYCN in humanen Neuoblastomzellen durch Transkriptionsfaktoren der E2F-Familie

Seit fast 30 Jahren ist bekannt, dass die Amplifikation und Expression des Onkogens MYCN in Neuroblastomen mit einer sehr ungünstigen Prognose für die Patienten einhergeht. Dennoch liegen die Mechanismen der Genregulation von MYCN weiterhin größtenteils im Dunkeln. Die Präsenz potentieller Bindungsstellen für E2F-Proteine im Promotor des MYCN-Gens sowie Zellkulturexperimente lieferten Hinweise auf eine Rolle der Transkriptionsfaktoren der E2F-Familie in der Regulation der N-myc-Expression. Ziel dieser Arbeit war die Beantwortung der Frage, ob E2F-Proteine notwendig sind, um eine primär hohe Expression von N-myc in Neuroblastomzellen mit Amplifikation des Onkogens aufrechtzuerhalten, und ob sie hinreichend sind, um die Transkription von MYCN in Zellen ohne endogene Expression von N-myc einzuleiten. Durch Überexpression des Tumorsuppressorproteins p16, welches zu einer Inaktivierung endogener E2F-Proteine führt, konnte die MYCN-mRNA-Menge in Neuroblastomzellen deutlich gesenkt werden. Vergleichbare Resultate wurden durch Expression von dominant negativem E2F-1 erzielt. Da in einigen Studien gezeigt werden konnte, dass Myc-Proteine ihrerseits E2F-Gene aktivieren können, nehmen wir an, in aggressiven Neuroblastomen könnte eine positive Rückkopplungsschleife zwischen E2F-Transkriptionsfaktoren auf der einen und N-myc auf der anderen Seite existieren, die die gesteigerte Aktivität des MYCN-Onkogens aufrechterhält. Stabil transfizierte E2F-ER-Fusionsproteine waren jedoch nicht in der Lage, das endogene MYCN-Gen in Neuroblastomzellen ohne Expression von N-myc anzuschalten. E2F-Proteine werden folglich für das volle Ausmaß der starken Expression von N-myc in Neuroblastomen benötigt, sind aber nicht ausreichend, um das Onkogen MYCN in Zellen ohne endogenes N-myc zu aktivieren. In der Zukunft könnte durch Verhinderung der Bindung von E2F-Proteinen an den MYCN-Promotor oder durch gentherapeutische Ansätze, die z.B. mittels viraler Infektion den Signalweg zwischen p16 und E2F rekonstruieren, die Expression von N-myc in Neuroblastomen gesenkt werden, so dass die Aggressivität der Tumore reduziert und die individuelle Prognose der Patienten verbessert werden könnte

TephraKam: geochemical database of glass compositions in tephra and welded tuffs from the Kamchatka volcanic arc (northwestern Pacific)

Tephra layers produced by volcanic eruptions are widely used for correlation and dating of various deposits and landforms, for synchronization of disparate paleoenvironmental archives, and for reconstruction of magma origin. Here we present our original database TephraKam, which includes chemical compositions of volcanic glass in tephra and welded tuffs from the Kamchatka volcanic arc. The database contains 7049 major element analyses obtained by electron microprobe and 738 trace element analyses obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on 487 samples collected in proximity of their volcanic sources in all volcanic zones in Kamchatka. The samples characterize about 300 explosive eruptions, which occurred in Kamchatka from the Pliocene until historic times. Precise or estimated ages for all samples are based on published 39Ar/40Ar dates of rocks and 14C dates of host sediments, statistical age modelling and geologic relationships with dated units. All data in TephraKam is supported by information about source volcanoes and analytical details. Using the data, we present an overview of geochemical variations of Kamchatka volcanic glasses and discuss application of this data for precise identification of tephra layers, their source volcanoes, temporal and spatial geochemical variations of pyroclastic rocks in Kamchatka

MIGHTEE-HI: the HI Size-Mass relation over the last billion years

We present the observed HI size-mass relation of $204$ galaxies from the MIGHTEE Survey Early Science data. The high sensitivity of MeerKAT allows us to detect galaxies spanning more than 4 orders of magnitude in HI mass, ranging from dwarf galaxies to massive spirals, and including all morphological types. This is the first time the relation has been explored on a blind homogeneous data set which extends over a previously unexplored redshift range of $0 < z < 0.084$, i.e. a period of around one billion years in cosmic time. The sample follows the same tight logarithmic relation derived from previous work, between the diameter ($D_{\rm HI}$) and the mass ($M_{\rm HI}$) of HI discs. We measure a slope of $0.501\pm 0.008$, an intercept of $-3.252^{+0.073}_{-0.074}$, and an observed scatter of $0.057$ dex. For the first time, we quantify the intrinsic scatter of $0.054 \pm 0.003$ dex (${\sim} 10 \%$), which provides a constraint for cosmological simulations of galaxy formation and evolution. We derive the relation as a function of galaxy type and find that their intrinsic scatters and slopes are consistent within the errors. We also calculate the $D_{\rm HI} - M_{\rm HI}$ relation for two redshift bins and do not find any evidence for evolution with redshift. These results suggest that over a period of one billion years in lookback time, galaxy discs have not undergone significant evolution in their gas distribution and mean surface mass density, indicating a lack of dependence on both morphological type and redshift.Comment: 10 pages, 5 figures, accepted for publication in MNRA

MIGHTEE-HI: The first MeerKAT HI mass function from an untargeted interferometric survey

We present the first measurement of the HI mass function (HIMF) using data from MeerKAT, based on 276 direct detections from the MIGHTEE Survey Early Science data covering a period of approximately a billion years ($0 \leq z \leq 0.084$). This is the first HIMF measured using interferometric data over non-group or cluster field, i.e. a deep blank field. We constrain the parameters of the Schechter function which describes the HIMF with two different methods: $1/\rm V_{\rm max}$ and Modified Maximum Likelihood (MML). We find a low-mass slope $\alpha=-1.29^{+0.37}_{-0.26}$, `knee' mass $\log_{10}(M_{*}/{\rm M_{\odot}}) = 10.07^{+0.24}_{-0.24}$ and normalisation $\log_{10}(\phi_{*}/\rm Mpc^{-3})=-2.34^{+0.32}_{-0.36}$ ($H_0 = 67.4$ kms$^{-1}$ Mpc$^{-1}$) for $1/\rm V_{\rm max}$ and $\alpha=-1.44^{+0.13}_{-0.10}$, `knee' mass $\log_{10}(M_{*}/{\rm M_{\odot}}) = 10.22^{+0.10}_{-0.13}$ and normalisation $\log_{10}(\phi_{*}/\rm Mpc^{-3})=-2.52^{+0.19}_{-0.14}$ for MML. When using $1/\rm V_{\rm max}$ we find both the low-mass slope and `knee' mass to be consistent within $1\sigma$ with previous studies based on single-dish surveys. The cosmological mass density of HI is found to be slightly larger than previously reported: $\Omega_{\rm HI}=5.46^{+0.94}_{-0.99} \times 10^{-4}h^{-1}_{67.4}$ from $1/\rm V_{\rm max}$ and $\Omega_{\rm HI}=6.31^{+0.31}_{-0.31} \times 10^{-4}h^{-1}_{67.4}$ from MML but consistent within the uncertainties. We find no evidence for evolution of the HIMF over the last billion years.Comment: 13 pages, 9 figures, accepted for publication in MNRA

MIGHTEE-HI : discovery of an H I-rich galaxy group at z = 0.044 with MeerKAT

We present the serendipitous discovery of a galaxy group in the XMM-LSS field with MIGHTEE Early Science observations. 20 galaxies are detected in H I in this z ∼ 0.044 group, with a 3σ column density sensitivity of NH I = 1.6 × 1020 cm−2. This group has not been previously identified, despite residing in a well-studied extragalactic legacy field. We present spatially resolved H I total intensity and velocity maps for each of the objects which reveal environmental influence through disturbed morphologies. The group has a dynamical mass of log10(Mdyn/M) = 12.32, and is unusually gas-rich, with an H I-to-stellar mass ratio of log10(f ∗ H I ) = −0.2, which is 0.7 dex greater than expected. The group’s high H I content, spatial, velocity, and identified galaxy type distributions strongly suggest that it is in the early stages of its assembly. The discovery of this galaxy group is an example of the importance of mapping spatially resolved H I in a wide range of environments, including galaxy groups. This scientific goal has been dramatically enhanced by the high sensitivity, large field-of-view, and wide instantaneous bandwidth of the MeerKAT telescope.http://mnras.oxfordjournals.orgpm2021Physic