7 research outputs found
MIGHTEE-HI: the HI Size-Mass relation over the last billion years
We present the observed HI size-mass relation of 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 , 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 () and the mass () of HI discs. We measure
a slope of , an intercept of , and an
observed scatter of dex. For the first time, we quantify the intrinsic
scatter of dex (), 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 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 (). 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: and Modified Maximum Likelihood (MML).
We find a low-mass slope , `knee' mass
and normalisation
(
kms Mpc) for and
, `knee' mass and normalisation for MML. When using we
find both the low-mass slope and `knee' mass to be consistent within
with previous studies based on single-dish surveys. The cosmological mass
density of HI is found to be slightly larger than previously reported:
from and 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: HI galaxy properties in the large scale structure environment at z~0.37 from a stacking experiment
We present the first measurement of HI mass of star-forming galaxies in
different large scale structure environments from a blind survey at . In particular, we carry out a spectral line stacking analysis
considering spectra of colour-selected star-forming galaxies undetected
in HI at in the COSMOS field, extracted from the MIGHTEE-HI
Early Science datacubes, acquired with the MeerKAT radio telescope. We stack
galaxies belonging to different subsamples depending on three different
definitions of large scale structure environment: local galaxy overdensity,
position inside the host dark matter halo (central, satellite, or isolated),
and cosmic web type (field, filament, or knot). We first stack the full
star-forming galaxy sample and find a robust HI detection yielding an average
galaxy HI mass of at
. Next, we investigate the different subsamples finding a
negligible difference in as a function of the galaxy overdensity.
We report an HI excess compared to the full sample in satellite galaxies
(, at ) and in
filaments (. Conversely, we report
non-detections for the central and knot galaxies subsamples, which appear to be
HI-deficient. We find the same qualitative results also when stacking in units
of HI fraction (). We conclude that the HI amount in star-forming
galaxies at the studied redshifts correlates with the large scale structure
environment.Comment: Accepted for publication in MNRAS. 15 figures, 3 table
MIGHTEE-\HI: Possible interactions with the galaxy NGC~895
The transformation and evolution of a galaxy is strongly influenced by
interactions with its environment. Neutral hydrogen (\HI) is an excellent way
to trace these interactions. Here, we present \HI\ observations of the spiral
galaxy NGC~895, which was previously thought to be isolated. High-sensitivity
\HI\ observations from the MeerKAT large survey project MIGHTEE reveal possible
interaction features, such as extended spiral arms, and the two newly
discovered \HI\ companions, that drive us to change the narrative that it is an
isolated galaxy. We combine these observations with deep optical images from
the Hyper Suprime Camera to show an absence of tidal debris between NGC 895 and
its companions. We do find an excess of light in the outer parts of the
companion galaxy MGTHJ022138.1-052631 which could be an indication of
external perturbation and thus possible sign of interactions. Our analysis
shows that NGC~895 is an actively star-forming galaxy with a SFR of
, a value typical for high stellar mass
galaxies on the star forming main sequence. It is reasonable to state that
different mechanisms may have contributed to the observed features in NGC~895
and this emphasizes the need to revisit the target with more detailed
observations. Our work shows the high potential and synergy of using
state-of-the-art data in both \HI\ and optical to reveal a more complete
picture of galaxy environments.Comment: 14 pages, 10 figures. Accepted for publication in MNRA
MIGHTEE-Hi: Evolution of Hi Scaling Relations of Star-forming Galaxies at z < 0.5*
We present the first measurements of H I galaxy scaling relations from a blind survey at z > 0.15. We perform spectral stacking of 9023 spectra of star-forming galaxies undetected in H I at 0.23 < z < 0.49, extracted from MIGHTEE-H I Early Science data cubes, acquired with the MeerKAT radio telescope. We stack galaxies in bins of galaxy properties (stellar mass M *, star formation rateSFR, and specific star formation rate sSFR, with sSFR ≡ M */SFR), obtaining ≳5σ detections in most cases, the strongest H I-stacking detections to date in this redshift range. With these detections, we are able to measure scaling relations in the probed redshift interval, finding evidence for a moderate evolution from the median redshift of our sample z med ~ 0.37 to z ~ 0. In particular, low-M * galaxies ( {\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })\sim 9 )experienceastrongHIdepletion( 0.5dexinlog10(MHI/M⊙)
), while massive galaxies ( {\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })\sim 11$ ) keep their H I mass nearly unchanged. When looking at the star formation activity, highly star-forming galaxies evolve significantly in M H I (f H I, where f H I ≡ M H I/M *) at fixed SFR (sSFR), while at the lowest probed SFR (sSFR) the scaling relations show no evolution. These findings suggest a scenario in which low-M * galaxies have experienced a strong H I depletion during the last ~5 Gyr, while massive galaxies have undergone a significant H I replenishment through some accretion mechanism, possibly minor mergers. Interestingly, our results are in good agreement with the predictions of the SIMBA simulation. We conclude that this work sets novel important observational constraints on galaxy scaling relations
MIGHTEE-H\u2009i: the baryonic Tully\u2013Fisher relation over the last billion years
Using a sample of 67 galaxies from the MeerKAT International GigaHertz Tiered Extragalactic Exploration Survey Early Science data, we study the H\u2009i-based baryonic Tully\u2013Fisher relation (bTFr), covering a period of 3c1 billion years (0 64 z 64 0.081). We consider the bTFr based on two different rotational velocity measures: the width of the global H\u2009i profile and Vout, measured as the outermost rotational velocity from the resolved H\u2009i rotation curves. Both relations exhibit very low intrinsic scatter orthogonal to the best-fitting relation (\u3c3 a5 = 0.07 \ub1 0.01), comparable to the SPARC sample at z 43 0. The slopes of the relations are similar and consistent with the z 43 0 studies (\u20603.66+0.35 120.29 for W50 and 3.47+0.37 120.30 for Vout). We find no evidence that the bTFr has evolved over the last billion years, and all galaxies in our sample are consistent with the same relation independent of redshift and the rotational velocity measure. Our results set-up a reference for all future studies of the H\u2009i-based bTFr as a function of redshift that will be conducted with the ongoing deep SKA pathfinders surveys
MIGHTEE-HI: The relation over the last billion years
We measure the relation over the last billion years
down to using the MIGHTEE Early Science data
with a Bayesian technique. This technique is applied to the HI detections,
without binning the datasets, while taking account of the intrinsic scatter in
the relation. We divide the full sample of 249 galaxies
into 161 spirals, 64 irregulars, 15 mergers, and 9 elliptical galaxies to
measure their relations. We fit this relation with both
linear and non-linear models, and find that the non-linear model is preferred
over the linear one for the full HI-selected sample with a measured transition
stellar mass of / = ,
beyond which the measured slope flattens. This finding supports the view that
the lack of HI gas is ultimately responsible for the decreasing star formation
rate observed in the massive main sequence galaxies. For the spiral galaxies
alone, which are biased towards those galaxies with the highest stellar masses
in our sample, the slope beyond the transition mass is shallower than for the
full sample, indicative of distinct gas processes ongoing for the
spirals/high-mass galaxies from other types of galaxies with lower stellar
masses. We also observe a moderate evolution of the
relation when splitting our samples into two redshift bins over the last
billion years, which can largely be attributed to the effect of sample
selection and hence highlights the potential of the full MIGHTEE survey.Comment: 14 pages, submitted to MNRA