The Galactic center is the most active site of star formation in the Milky Way, where particularly high-mass stars have formed very recently and are still forming today. However, since we are looking ...at the Galactic center through the Galactic disk, knowledge of extinction is crucial when studying this region. The Arches cluster is a young, massive starburst cluster near the Galactic center. We observed the Arches cluster out to its tidal radius using Ks-band imaging obtained with NAOS/CONICA at the VLT combined with Subaru/CISCO J-band data to gain a full understanding of the cluster mass distribution. We show that the determination of the mass of the most massive star in the Arches cluster, which had been used in previous studies to establish an upper mass limit for the star formation process in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes of widely used infrared extinction laws, we show that the difference can reach up to 30% for individually derived stellar masses and ΔAKs ~ 1 magnitude in acquired Ks-band extinction, while the present-day mass function slope changes by ~ 0.17 dex. The present-day mass function slope derived assuming the more recent extinction law increases from a flat slope of αNishi = −1.50 ± 0.35 in the core (r < 0.2 pc) to αNishi = −2.21 ± 0.27 in the intermediate annulus (0.2 < r < 0.4 pc), where the Salpeter slope is –2.3. The mass function steepens to αNishi = −3.21 ± 0.30 in the outer annulus (0.4 < r < 1.5 pc), indicating that the outer cluster region is depleted of high-mass stars. This picture is consistent with mass segregation owing to the dynamical evolution of the cluster.
Submillimeter/millimeter observations of dusty star-forming galaxies with the Atacama Large Millimeter/submillimeter Array (ALMA) have shown that dust continuum emission generally occurs in compact ...regions smaller than the stellar distribution. However, it remains to be understood how systematic these findings are. Studies often lack homogeneity in the sample selection, target discontinuous areas with inhomogeneous sensitivities, and suffer from modest
u
v
coverage coming from single array configurations. GOODS-ALMA is a 1.1 mm galaxy survey over a continuous area of 72.42 arcmin
2
at a homogeneous sensitivity. In this version 2.0, we present a new low resolution dataset and its combination with the previous high resolution dataset from the survey, improving the
u
v
coverage and sensitivity reaching an average of
σ
= 68.4 μJy beam
−1
. A total of 88 galaxies are detected in a blind search (compared to 35 in the high resolution dataset alone), 50% at
S
/
N
peak
≥ 5 and 50% at 3.5 ≤
S
/
N
peak
≤ 5 aided by priors. Among them, 13 out of the 88 are optically dark or faint sources (
H
- or
K
-band dropouts). The sample dust continuum sizes at 1.1 mm are generally compact, with a median effective radius of
R
e
= 0
.
″
10 ± 0
.
″
05 (a physical size of
R
e
= 0.73 ± 0.29 kpc at the redshift of each source). Dust continuum sizes evolve with redshift and stellar mass resembling the trends of the stellar sizes measured at optical wavelengths, albeit a lower normalization compared to those of late-type galaxies. We conclude that for sources with flux densities
S
1.1 mm
> 1 mJy, compact dust continuum emission at 1.1 mm prevails, and sizes as extended as typical star-forming stellar disks are rare. The
S
1.1 mm
< 1 mJy sources appear slightly more extended at 1.1 mm, although they are still generally compact below the sizes of typical star-forming stellar disks.
We investigate the properties of a sample of 35 galaxies, detected with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 1.1 mm in the GOODS-ALMA field (area of 69 arcmin
2
, resolution = ...0.60″, rms ≃ 0.18 mJy beam
−1
). Using the ultraviolet-to-radio deep multiwavelength coverage of the GOODS–South field, we fit the spectral energy distributions of these galaxies to derive their key physical properties. The galaxies detected by ALMA are among the most massive at
z
= 2−4 (
M
⋆, med
= 8.5 × 10
10
M
⊙
) and they are either starburst or located in the upper part of the galaxy star-forming main sequence. A significant portion of our galaxy population (∼40%), located at
z
∼ 2.5 − 3, exhibits abnormally low gas fractions. The sizes of these galaxies, measured with ALMA, are compatible with the trend between the rest-frame 5000 Å size and stellar mass observed for
z
∼ 2 elliptical galaxies, suggesting that they are building compact bulges. We show that there is a strong link between star formation surface density (at 1.1 mm) and gas depletion time: The more compact a galaxy’s star-forming region is, the shorter its lifetime will be (without gas replenishment). The identified compact sources associated with relatively short depletion timescales (∼100 Myr) are the ideal candidates to be the progenitors of compact elliptical galaxies at
z
∼ 2.
Thanks to its outstanding angular resolution, the Atacama Large Millimeter/submillimeter Array (ALMA) has recently unambiguously identified a population of optically dark galaxies with redshifts ...greater than
z
= 3, which play an important role in the cosmic star formation in massive galaxies. In this paper we study the properties of the six optically dark galaxies detected in the 69 arcmin
2
GOODS-ALMA 1.1 mm continuum survey. While none of them are listed in the deepest
H
-band based CANDELS catalog in the GOODS-South field down to
H
= 28.16 AB, we were able to de-blend two of them from their bright neighbor and measure an
H
-band flux for them. We present the spectroscopic scan follow-up of five of the six sources with ALMA band 4. All are detected in the 2 mm continuum with signal-to-noise ratios higher than eight. One emission line is detected in AGS4 (
ν
obs
= 151.44 GHz with an
S
/
N
= 8.58) and AGS17 (
ν
obs
= 154.78 GHz with an
S
/
N
= 10.23), which we interpret in both cases as being due to the CO(6–5) line at
z
spec
AGS4
= 3.556 and
z
spec
AGS17
= 3.467, respectively. These redshifts match both the probability distribution of the photometric redshifts derived from the UV to near-infrared spectral energy distributions (SEDs) and the far-infrared SEDs for typical dust temperatures of galaxies at these redshifts. We present evidence that nearly 70% (4/6 of galaxies) of the optically dark galaxies belong to the same overdensity of galaxies at
z
∼ 3.5. overdensity The most massive one, AGS24 (
M
⋆
= 10
11.32
−0.19
+0.02
M
⊙
), is the most massive galaxy without an active galactic nucleus at
z
> 3 in the GOODS-ALMA field. It falls in the very center of the peak of the galaxy surface density, which suggests that the surrounding overdensity is a proto-cluster in the process of virialization and that AGS24 is the candidate progenitor of the future brightest cluster galaxy.
Abstract
We present 0.97 × 0.53 arcsec2 (470 pc × 250 pc) resolution CO (J = 2–1) observations towards the nearby luminous merging galaxy NGC 6240 with the Atacama Large Millimeter/submillimeter ...Array. We confirmed a strong CO concentration within the central 700 pc, which peaks between the double nuclei, surrounded by extended CO features along the optical dust lanes (∼11 kpc). We found that the CO emission around the central, a few kpc, has extremely broad velocity wings with full width at zero intensity ∼ 2000 km s−1, suggesting a possible signature of molecular outflow(s). In order to extract and visualize the high-velocity components in NGC 6240, we performed a multiple Gaussian fit to the CO data cube. The distribution of the broad CO components shows four extremely large line width regions (∼1000 km s−1) located 1–2 kpc away from both nuclei. Spatial coincidence of the large line width regions with H α, near-IR H2, and X-ray suggests that the broad CO (2–1) components are associated with nuclear outflows launched from the double nuclei.
We present the results of new near-IR spectroscopic observations of passive galaxies at z > ~ 1.4 in a concentration of BzK-selected galaxies in the COSMOS field. The observations have been conducted ...with Subaru/MOIRCS, and have resulted in absorption lines and/or continuum detection for 18 out of 34 objects. This allows us to measure spectroscopic redshifts for a sample that is almost complete to K sub(AB) = 21. COSMOS photometric redshifts are found in fair agreement overall with the spectroscopic redshifts, with a standard deviation of ~0.05; however, ~30% of objects have photometric redshifts systematically underestimated by up to ~25%. We show that these systematic offsets in photometric redshifts can be removed by using these objects as a training set. All galaxies fall in four distinct redshift spikes at z = 1.43, 1.53, 1.67, and 1.82, with this latter one including seven galaxies. SED fits to broadband fluxes indicate stellar masses in the range of ~4-40 x 10 super(10) M sub(middot in circle) and that star formation was quenched ~1 Gyr before the cosmic epoch at which they are observed. The spectra of several individual galaxies have allowed us to measure their H delta sub(F) indices and the strengths of the 4000 Angstrom break, which confirms their identification as passive galaxies, as does a composite spectrum resulting from the co-addition of 17 individual spectra. The effective radii of the galaxies have been measured on the COSMOS HST/ACS i sub(F814W)-band image, confirming the coexistence at these redshifts of passive galaxies, which are substantially more compact than their local counterparts with others that follow the local effective radius-stellar mass relation. For the galaxy with the best signal-to-noise spectrum we were able to measure a velocity dispersion of 270 + or - 105 km s super(-1) (error bar including systematic errors), indicating that this galaxy lies closely on the virial relation given its stellar mass and effective radius.
Context.
A rich population of low-mass brown dwarfs and isolated planetary mass objects has been reported in the Upper Scorpius and Ophiuchus star-forming complex.
Aims.
We investigate the ...membership, nature, and properties of 17 of these isolated planetary mass candidates using low-resolution near-infrared spectra.
Methods.
We investigated the membership by looking for evidence of their youth using four diagnostics: the slope of the continuum between the
J
and
Ks
band, the
H
cont
, and the TLI-g gravity-sensitive indices. In addition, we compared the spectra to young and field (old) M and L-dwarf standards.
Results.
All the targets but one are confirmed as young ultracool objects, with spectral types between L0 and L6 and masses in the range 0.004–0.013
M
⊙
, according to evolutionary models. The status of the last target is unclear at this point.
Conclusions.
Only one possible contaminant has been identified among the 17 targets, suggesting that the contamination level of the original sample must be low (≲6%).
The spectral signatures of asymmetry in Type Ia Supernova (SN Ia) explosions are investigated, using a sample of late-time nebular spectra. First, a kinematical model is constructed for SN Ia 2003hv, ...which can account for the main features in its optical, Near-Infrared (NIR), and Mid-Infrared (Mid-IR) late-time spectra. It is found that an asymmetric off-center model can explain the observed characteristics of SN 2003hv. This model includes a relatively high-density, Fe-rich region which displays a large velocity off-set, and a relatively low density, extended 56Ni-rich region which is more spherically distributed. The high-density region consists of the inner stable Fe-Ni region and outer 56Ni-rich region. Such a distribution may be the result of a delayed-detonation explosion, in which the first deflagration produces the global asymmetry in the innermost ejecta, while the subsequent detonation can lead to the bulk spherical symmetry. This configuration, if viewed from the direction of the off-set, can consistently explain the blueshift in some of the emission lines and virtually no observed shift in other lines in SN 2003hv. For this model, we then explore the effects of different viewing angles and the implications for SNe Ia in general. The model predicts that a variation of the central wavelength, depending on the viewing angle, should be seen in some lines (e.g., Ni II Delta *l7378), while the strongest lines (e.g., Fe III blend at ~4700 A) will not show this effect. By examining optical nebular spectra of 12 SNe Ia, we have found that such a variation indeed exists. We suggest that the global asymmetry in the innermost ejecta, as likely imprint of the deflagration flame propagation, is a generic feature of SNe Ia. It is also shown that various forbidden lines in the NIR and Mid-IR regimes provide strong diagnostics to further constrain the explosion geometry and thus the explosion mechanism.
In this paper, we extend the source detection in the GOODS-ALMA field (69 arcmin
2
, 1
σ
≃ 0.18 mJy beam
−1
) to deeper levels than presented in our previous work. Using positional information at 3.6 ...and 4.5
μ
m (from
Spitzer
-IRAC) as well as the Very Large Array (VLA) at 3 GHz, we explore the presence of galaxies detected at 1.1 mm with ALMA below our original blind detection limit of 4.8-
σ
, at which the number of spurious sources starts to dominate over that of real sources. In order to ensure the most reliable counterpart association possible, we have investigated the astrometry differences between different instruments in the GOODS–South field. In addition to a global offset between the Atacama Large Millimeter/submillimeter Array (ALMA) and the
Hubble
Space Telescope (HST) already discussed in previous studies, we have highlighted a local offset between ALMA and the HST that was artificially introduced in the process of building the mosaic of the GOODS–South image. We created a distortion map that can be used to correct for these astrometric issues. In this Supplementary Catalog, we find a total of 16 galaxies, including two galaxies with no counterpart in HST images (also known as optically dark galaxies), down to a 5
σ
limiting depth of
H
= 28.2 AB (HST/WFC3
F
160
W
). This brings the total sample of GOODS-ALMA 1.1 mm sources to 35 galaxies. Galaxies in the new sample cover a wider dynamic range in redshift (
z
= 0.65−4.73), are on average twice as large (1.3 vs 0.65 kpc), and have lower stellar masses (
M
⋆
SC
= 7.6 × 10
10
M
⊙
vs
M
⋆
MC
= 1.2 × 10
11
M
⊙
). Although exhibiting larger physical sizes, these galaxies still have far-infrared sizes that are significantly more compact than inferred from their optical emission.
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