46 research outputs found
The MUSE-Faint survey. IV. Dissecting Leo T, a gas-rich relic with recent star formation
Leo T () is both the faintest and the least massive galaxy known
to contain neutral gas and to display signs of recent star formation. We
analyse photometry and stellar spectra to identify member stars and to better
understand the overall dynamics and stellar content of the galaxy and to
compare the properties of its young and old stars. We use data from the Multi
Unit Spectroscopic Explorer (MUSE) on the VLT. We supplement this information
with spectroscopic data from the literature and with Hubble Space Telescope
(HST) photometry. Our analysis reveals two distinct populations of stars in Leo
T. The first population, with an age of , includes
three emission-line Be stars comprising 15% of the total number of young stars.
The second population of stars is much older, with ages ranging from
to as high as . We combine MUSE data with
literature data to obtain an overall velocity dispersion of for Leo T. When we divide the sample
of stars into young and old populations, we find that they have distinct
kinematics. Specifically, the young population has a velocity dispersion of
, contrasting with that of the old
population, of . The fact that the
kinematics of the cold neutral gas is in good agreement with the kinematics of
the young population suggests that the recent star formation in Leo T is linked
with the cold neutral gas. We assess the existence of extended emission-line
regions and find none to a surface brightness limit of~
which corresponds to an upper limit on star formation of , implying that the star formation in
Leo T has ended.Comment: Accepted for publication in A&A on 04-08-2023. 17 pages, 17 figures,
3 table
The MUSE-Faint survey. V. Constraining Scalar Field Dark Matter with Antlia B
Aims. We use stellar line-of-sight velocities of Antlia B, a faint dwarf
galaxy in the NGC 3109 association, to derive constraints on the fundamental
properties of scalar field dark matter originally proposed to solve the
small-scale problems faced by cold dark matter models. Methods. We use the
first spectroscopic observations of Antlia B, a distant (d 1.35 Mpc)
faint dwarf (, MM), from
MUSE-Faint - a survey of ultra-faint dwarfs with the Multi Unit Spectroscopic
Explorer. Through measurement of line-of-sight velocities for stars in the
field-of-view, we identify 127 stars as members of Antlia B,
allowing us to model its dark matter density profile with the Jeans modelling
code GravSphere. We implement a model for scalar field dark matter into
GravSphere and use this to place constraints on the self-coupling strength of
this model. Results. We find a virial mass of M and a concentration parameter of
for Antlia B. These results are
consistent with the mass-concentration relations in the literature. We
constrain the characteristic length scale of the repulsive self-interaction
of the scalar field dark matter model to pc (68% confidence level), which translates to a self-coupling
strength of eVcm. The
constraint on the characteristic length scale of the repulsive self-interaction
is inconsistent with the value required to match the observations of cores of
dwarf galaxies in the Local Group, suggesting that the cored density profiles
of those galaxies are not caused by scalar field dark matter.Comment: Accepted for publication in A&A on 21-07-2023. 17 pages, 22 figures,
4 table
A NOEMA molecular line scan of the Hubble Deep Field North: Improved constraints on the CO luminosity functions and cosmic density of molecular gas
We present measurements of the CO luminosity functions (LFs) and the
evolution of the cosmic molecular gas density out to z~6 based on an 8.5
arcmin^2 spectral scan survey at 3mm of the iconic Hubble Deep Field North
(HDF-N) observed with the NOrthern Extended Millimeter Array (NOEMA). We use
matched filtering to search for line emission from galaxies and determine their
redshift probability distributions exploiting the extensive multi-wavelength
data for the HDF-N. We identify the 7 highest-fidelity sources as CO emitters
at 1<z<6, including the well-known submillimeter galaxy HDF850.1 at z=5.18.
Four high-fidelity 3mm continuum sources are all found to be radio galaxies at
z<=1, plus HDF850.1. We constrain the CO LFs in the HDF-N out to z~6, including
a first measurement of the CO(5-4) LF at =5.0. The relatively large area and
depth of the NOEMA HDF-N survey extends the existing luminosity functions at
1<z<4 above the knee, yielding a somewhat lower density by 0.15-0.4 dex at the
overlap region for the CO(2-1) and CO(3-2) transitions, attributed to cosmic
variance. We perform a joint analysis of the CO LFs in the HDF-N and Hubble
Ultra Deep Field from ASPECS, finding that they can be well described by a
single Schechter function. The evolution of the cosmic molecular gas density
from a joint analysis is in good agreement with earlier determinations. This
implies that the impact of cosmic field-to-field variance on the measurements
is consistent with previous estimates, adding to the challenges for simulations
that model galaxies from first principles.Comment: 19 pages, 13 figures, 7 tables. Accepted for publication in the
Astrophysical Journal (ApJ
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: CO Excitation and Atomic Carbon in Star-forming Galaxies at z = 1–3
We investigate the CO excitation and interstellar medium (ISM) conditions in a cold gas mass-selected sample of 22 star-forming galaxies at z = 0.46–3.60, observed as part of the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). Combined with Very Large Array follow-up observations, we detect a total of 34 CO transitions with J = 1 up to 8 (and an additional 21 upper limits, up to J = 10) and 6 and transitions (and 12 upper limits). The CO(2–1) and CO(3–2)-selected galaxies, at and 2.5, respectively, exhibit a range in excitation in their mid-J = 4, 5 and high-J = 7, 8 lines, on average lower than (-brighter) BzK-color- and submillimeter-selected galaxies at similar redshifts. The former implies that a warm ISM component is not necessarily prevalent in gas mass-selected galaxies at . We use stacking and Large Velocity Gradient models to measure and predict the average CO ladders at z < 2 and z ≥ 2, finding and , respectively. From the models, we infer that the galaxies at z ≥ 2 have intrinsically higher excitation than those at z < 2. This fits a picture in which the global excitation is driven by an increase in the star formation rate surface density of galaxies with redshift. We derive a neutral atomic carbon abundance of , comparable to the Milky Way and main-sequence galaxies at similar redshifts, and fairly high densities (≥104 cm−3), consistent with the low-J CO excitation. Our results imply a decrease in the cosmic molecular gas mass density at z ≥ 2 compared to previous ASPECS measurements
Dual constraints with ALMA: new [O III] 88 m and dust-continuum observations reveal the ISM conditions of luminous LBGs at
We present new [O III] 88 m observations of five bright
Lyman-break galaxies spectroscopically confirmed by ALMA through the [C II] 158
m line, unlike recent [O III] detections where Lyman-
was used. This nearly doubles the sample of Epoch of Reionisation galaxies with
robust () detections of [C II] and [O III]. We perform a
multi-wavelength comparison with new deep HST images of the rest-frame UV,
whose compact morphology aligns well with [O III] tracing ionised gas. By
contrast, we find more spatially extended [C II] emission likely produced in
neutral gas, as indicated by a [N II] 205 m non-detection in one
source. We find a positive correlation between the equivalent width of the
optical [O III] and H lines and the [O III]/[C II] ratio, as seen
in local metal-poor dwarf galaxies. Cloudy models of a nebula of typical
density harbouring a young stellar population with a high ionisation parameter
appear to adequately reproduce the far-infrared lines. Surprisingly, however,
our models fail to reproduce the strength of [O III] 88 m, unless we
assume an /Fe enhancement and a near-solar nebular oxygen
abundance. On spatially resolved scales, we find [O III]/[C II] shows a
tentative anti-correlation with infrared excess, , also
seen on global scales in the local Universe. Finally, we introduce the
far-infrared spectral energy distribution fitting code MERCURIUS to show that
dust-continuum measurements of one source appear to favour a low dust
temperature coupled with a high dust mass. This implies a high stellar
metallicity yield and may point towards the need of dust production or
grain-growth mechanisms beyond supernovae.Comment: 23 pages, 11 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
The ALMA Spectroscopic Survey in the HUDF: Deep 1.2 mm Continuum Number Counts
We present the results from the 1.2 mm continuum image obtained as part of the Atacama Large Millimeter/submillimeter Array Spectroscopic Survey in the Hubble Ultra Deep Field. The 1.2 mm continuum image has a size of 2.9 (4.2) arcmin2 within a primary beam response of 50% (10%) and an rms value of . We detect 35 sources at high significance (Fidelity ≥0.5); 32 have well-characterized near-infrared Hubble Space Telescope counterparts. We estimate the 1.2 mm number counts to flux levels of in two different ways: we first use the detected sources to constrain the number counts and find a significant flattening of the counts below S ν ~ 0.1 mJy. In a second approach, we constrain the number counts using a probability of deflection statistics (P(D)) analysis. For this latter approach, we describe new methods to accurately measure the noise in interferometric imaging (employing jackknifing in the cube and in the visibility plane). This independent measurement confirms the flattening of the number counts. Our analysis of the differential number counts shows that we are detecting ~93% (~100% if we include the lower fidelity detections) of the total continuum dust emission associated with galaxies in the Hubble Ultra Deep Field. The ancillary data allow us to study the dependence of the 1.2 mm number counts on redshift (z = 0−4), galaxy dust mass ({M}_{\mathrm{dust}}={10}^{7}\mbox{--}{10}^{9}{M}_{\odot }), stellar mass ({M}_{* }={10}^{9}\mbox{--}{10}^{12}{M}_{\odot }), and star formation rate (). In an accompanying paper we show that the number counts are crucial to constrain galaxy evolution models and the understanding of star-forming galaxies at high redshift.M.N. and F.W. acknowledge support
from ERC Advanced grant 740246 (Cosmic Gas). D.R.
acknowledges support from the National Science Foundation
under grant no. AST-1614213 and from the Alexander von
Humboldt Foundation through a Humboldt Research Fellowship for Experienced Researchers. R.J.A. was supported by
FONDECYT grant number 1191124. I.R.S. acknowledges
support from STFC (ST/P000541/1). B.M. acknowledge
support from the Collaborative Research Centre 956, subproject A1, funded by the Deutsche Forschungsgemeinschaft
(DFG)—project ID 184018867. We acknowledge support from
CONICYT grants CATA-Basal AFB-170002 (FEB); FONDECYT Regular 1190818 (FEB); Chile’s Ministry of Economy,
Development, and Tourism’s Millennium Science. Initiative
through grant IC120009, awarded to The Millennium Institute
of Astrophysics, MAS (FEB). Este trabajo cont ó con el apoyo
de CONICYT + PCI + INSTITUTO MAX PLANCK DE
ASTRONOMIA MPG190030 (M.A.)
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: The Nature of the Faintest Dusty Star-forming Galaxies
We present a characterization of the physical properties of a sample of 35 securely detected, dusty galaxies in the deep ALMA 1.2 mm image obtained as part of the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) Large Program. This sample is complemented by 26 additional sources identified via an optical/infrared source positional prior. Using their well-characterized spectral energy distributions, we derive median stellar masses and star formation rates (SFR) of and 30 M ☉ yr−1, respectively, and interquartile ranges of (2.4-11.7) x 1010 M ☉ and 20-50 M ☉ yr−1. We derive a median spectroscopic redshift of 1.8 with an interquartile range 1.1-2.6, significantly lower than submillimeter galaxies detected in shallower, wide-field surveys. We find that 59% +- 13%, 6% +- 4%, and 34% +- 9% of our sources are within, above, and below+-0.4 dex from the SFR-stellar-mass relation or main sequence (MS), respectively. The ASPECS galaxies closely follow the SFR-molecular gas mass relation and other previously established scaling relations, confirming a factor of five increase of the gas-to-stellar-mass ratio from z = 0.5 to 2.5 and a mild evolution of the gas depletion timescales with a typical value of 0.7 Gyr at z = 1-3. ASPECS galaxies located significantly below the MS, a poorly exploited parameter space, have low gas-to-stellar-mass ratios of ~0.1-0.2 and long depletion timescales >1 Gyr. Galaxies along the MS dominate the cosmic density of molecular gas at all redshifts. Systems above the MS have an increasing contribution to the total gas reservoirs from z < 1 to z = 2.5, while the opposite is found for galaxies below the MS.M.A. has been supported by the grant “CONICYT + PCI +
INSTITUTO MAX PLANCK DE ASTRONOMIA
MPG190030” and “CONICYT+PCI+REDES 190194.”
J.G.-L. acknowledges partial support from ALMA-CONICYT
project 31160033. F.W. and M.N. acknowledge funding from
the ERC Advanced Grant “Cosmic Gas.” F.E.B. acknowledges
support from CONICYT grants CATA-Basal AFB-170002
(FEB), FONDECYT Regular 1190818 (FEB), 1200495 (FEB),
and Chile’s Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009,
awarded to The Millennium Institute of Astrophysics, MAS
(FEB). T.D.-S. acknowledges support from ALMA-CONICYT
project 31130005 and FONDECYT project 1151239. D.R.
acknowledges support from the National Science Foundation
under grant Nos. AST-1614213 and AST-1910107 and from
the Alexander von Humboldt Foundation through a Humboldt
Research Fellowship for Experienced Researchers. I.R.S.
acknowledges support from STFC (ST/P000541/1). L.H.I.
acknowledges support from JSPS KAKENHI grant No.
JP19K23462. The National Radio Astronomy Observatory is
a facility of the National Science Foundation operated under
cooperative agreement by Associated Universities, Inc. This
paper makes use of the following ALMA data: 2016.1.00324.
ALMA is a partnership of ESO (representing its member
states), NSF (USA), and NINS (Japan), together with NRC
(Canada), NSC and ASIAA (Taiwan), and KASI (Republic
of Korea), in cooperation with the Republic of Chile. The
Joint ALMA Observatory is operated by ESO, AUI/NRAO,
and NAOJ
MIDIS: JWST/MIRI reveals the Stellar Structure of ALMA-selected Galaxies in the Hubble-UDF at Cosmic Noon
We present deep James Webb Space Telescope (JWST)/MIRI F560W observations of
a flux-limited, ALMA-selected sample of 28 galaxies at z=0.5-3.6 in the Hubble
Ultra Deep Field (HUDF). The data from the MIRI Deep Imaging Survey (MIDIS)
reveal the stellar structure of the HUDF galaxies at rest-wavelengths of >1
micron for the first time. We revise the stellar mass estimates using new JWST
photometry and find good agreement with pre-JWST analysis; the few
discrepancies can be explained by blending issues in the earlier
lower-resolution Spitzer data. At z~2.5, the resolved rest-frame near-infrared
(1.6 micron) structure of the galaxies is significantly more smooth and
centrally concentrated than seen by HST at rest-frame 450 nm (F160W), with
effective radii of Re(F560W)=1-5 kpc and S\'ersic indices mostly close to an
exponential (disk-like) profile (n~1), up to n~5 (excluding AGN). We find an
average size ratio of Re(F560W)/Re(F160W)~0.7 that decreases with stellar mass.
The stellar structure of the ALMA-selected galaxies is indistinguishable from a
HUDF reference sample of galaxies with comparable MIRI flux density. We
supplement our analysis with custom-made, position-dependent, empirical PSF
models for the F560W observations. The results imply that an older and smoother
stellar structure is in place in massive gas-rich, star-forming galaxies at
Cosmic Noon, despite a more clumpy rest-frame optical appearance, placing
additional constraints on galaxy formation simulations. As a next step,
matched-resolution, resolved ALMA observations will be crucial to further link
the mass- and light-weighted galaxy structures to the dusty interstellar
medium.Comment: 19 pages, 10 figures, 1 table, submitted to Ap