Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we conducted a program to measure redshifts for 13 bright galaxies detected in the
Herschel
Astrophysical Large Area Survey with
S
500
μ
m
...≥ 80 mJy. We report reliable spectroscopic redshifts for 12 individual sources, which are derived from scans of the 3 and 2 mm bands, covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. The spectroscopic redshifts are in the range 2.08 <
z
< 4.05 with a median value of
z
= 2.9 ± 0.6. The sources are unresolved or barely resolved on scales of 10 kpc. In one field, two galaxies with different redshifts were detected. In two cases the sources are found to be binary galaxies with projected distances of ∼140 kpc. The linewidths of the sources are large, with a mean value for the full width at half maximum of 700 ± 300 km s
−1
and a median of 800 km s
−1
. We analyze the nature of the sources with currently available ancillary data to determine if they are lensed or hyper-luminous (
L
FIR
> 10
13
L
⊙
) galaxies. We also present a reanalysis of the spectral energy distributions including the continuum flux densities measured at 3 and 2 mm to derive the overall properties of the sources. Future prospects based on these efficient measurements of redshifts of high-
z
galaxies using NOEMA are outlined, including a comprehensive survey of all the brightest
Herschel
galaxies.
We combine new Herschel/SPIRE sub-millimeter observations with existing multiwavelength data to investigate the dust scaling relations of the Herschel Reference Survey, a magnitude-, volume-limited ...sample of ~300 nearby galaxies in different environments. We show that the dust-to-stellar mass ratio anti-correlates with stellar mass, stellar mass surface density and NUV − r colour across the whole range of parameters covered by our sample. Moreover, the dust-to-stellar mass ratio decreases significantly when moving from late- to early-type galaxies. These scaling relations are similar to those observed for the Hi gas-fraction, supporting the idea that the cold dust is tightly coupled to the cold atomic gas component in the interstellar medium. We also find a weak increase of the dust-to-Hi mass ratio with stellar mass and colour but no trend is seen with stellar mass surface density. By comparing galaxies in different environments we show that, although these scaling relations are followed by both cluster and field galaxies, Hi-deficient systems have, at fixed stellar mass, stellar mass surface density and morphological type systematically lower dust-to-stellar mass and higher dust-to-Hi mass ratios than Hi-normal/field galaxies. This provides clear evidence that dust is removed from the star-forming disk of cluster galaxies but the effect of the environment is less strong than what is observed in the case of the Hi disk. Such effects naturally arise if the dust disk is less extended than the Hi and follows more closely the distribution of the molecular gas phase, i.e., if the dust-to-atomic gas ratio monotonically decreases with distance from the galactic center.
Aims. Cool, evolved stars have copious, enriched winds. Observations have so far not fully constrained models for the shaping and acceleration of these winds. We need to understand the dynamics ...better, from the pulsating stellar surface to ~10 stellar radii, where radiation pressure on dust is fully effective. Asymmetric nebulae around some red supergiants imply the action of additional forces. Methods. We retrieved ALMA Science Verification data providing images of sub-mm line and continuum emission from VY CMa. This enables us to locate water masers with milli-arcsec accuracy and to resolve the dusty continuum. Results. The 658, 321, and 325 GHz masers lie in irregular, thick shells at increasing distances from the centre of expansion. For the first time this is confirmed as the stellar position, coinciding with a compact peak offset to the NW of the brightest continuum emission. The maser shells overlap but avoid each other on scales of up to 10 au. Their distribution is broadly consistent with excitation models but the conditions and kinematics are complicated by wind collisions, clumping, and asymmetries.
We present Herschel observations of 62 early-type galaxies (ETGs), including 39 galaxies morphologically classified as S0+S0a and 23 galaxies classified as ellipticals using SPIRE at 250, 350, and ...500 mu m as part of the volume-limited Herschel Reference Survey (HRS). We detect dust emission in 24% of the ellipticals and 62% of the S0s. The mean temperature of the dust is left angle bracketT sub(d)right angle bracket = 23.9 + or - 0.8 K, warmer than that found for late-type galaxies in the Virgo Cluster. The mean dust mass for the entire detected early-type sample is logM sub(d) = 6.1 + or - 0.1 M with a mean dust-to-stellar-mass ratio of log(M sub(d)/Ml ow *) = -4.3 + or - 0.1. Including the non-detections, these parameters are logM sub(d) = 5.6 + or - 0.1 and log(M sub(d)/Ml ow *) = -5.1 + or - 0.1, respectively. The average dust-to-stellar-mass ratio for the early-type sample is fifty times lower, with larger dispersion, than the spiral galaxies observed as part of the HRS, and there is an order-of-magnitude decline in M sub(d)/Mlow * between the S0s and ellipticals. We use UV and optical photometry to show that virtually all the galaxies lie close to the red sequence yet the large number of detections of cool dust, the gas-to-dust ratios, and the ratios of far-infrared to radio emission all suggest that many ETGs contain a cool interstellar medium similar to that in late-type galaxies. We show that the sizes of the dust sources in S0s are much smaller than those in early-type spirals and the decrease in the dust-to-stellar-mass ratio from early-type spirals to S0s cannot simply be explained by an increase in the bulge-to-disk ratio. These results suggest that the disks in S0s contain much less dust (and presumably gas) than the disks of early-type spirals and this cannot be explained simply by current environmental effects, such as ram-pressure stripping. The wide range in the dust-to-stellar-mass ratio for ETGs and the lack of a correlation between dust mass and optical luminosity suggest that much of the dust in the ETGs detected by Herschel has been acquired as the result of interactions, although we show these are unlikely to have had a major effect on the stellar masses of the ETGs. The Herschel observations tentatively suggest that in the most massive systems, the mass of interstellar medium is unconnected to the evolution of the stellar populations in these galaxies.
We present Herschel/PACS 100 and 160 μm integrated photometry for the 323 galaxies in the Herschel Reference Survey (HRS), a K-band, volume-limited sample of galaxies in the local Universe. Once ...combined with the Herschel/SPIRE observations already available, these data make the HRS the largest representative sample of nearby galaxies with homogeneous coverage across the 100-500 μm wavelength range. In this paper, we take advantage of this unique data set to investigate the properties and shape of the far-infrared/submillimetre spectral energy distribution in nearby galaxies. We show that, in the stellar mass range covered by the HRS (8 log (M
*/M) 12), the far-infrared/submillimetre colours are inconsistent with a single modified blackbody having the same dust emissivity index β for all galaxies. In particular, either β decreases or multiple temperature components are needed, when moving from metal-rich/gas-poor to metal-poor/gas-rich galaxies. We thus investigate how the dust temperature and mass obtained from a single modified blackbody depend on the assumptions made on β. We show that, while the correlations between dust temperature, galaxy structure and star formation rate are strongly model dependent, the dust mass scaling relations are much more reliable, and variations of β only change the strength of the observed trends.
The Herschel Virgo Cluster Survey (HeViCS) is the deepest, confusion-limited survey of the Virgo Cluster at far-infrared (FIR) wavelengths. The entire survey at full depth covers ∼55 deg2 in five ...bands (100-500 μm), encompassing the areas around the central dominant elliptical galaxies (M87, M86 and M49) and extends as far as the NW cloud, the W cloud and the Southern extension. The survey extends beyond this region with lower sensitivity so that the total area covered is 84 deg2. In this paper we describe the data, the data acquisition techniques and present the detection rates of the optically selected Virgo Cluster Catalogue (VCC). We detect 254 (34 per cent) of 750 VCC galaxies found within the survey boundary in at least one band and 171 galaxies are detected in all five bands. For the remainder of the galaxies we have measured strict upper limits for their FIR emission. The population of detected galaxies contains early as well as late types although the latter dominate the detection statistics. We have modelled 168 galaxies, showing no evidence of a strong synchrotron component in their FIR spectra, using a single-temperature modified blackbody spectrum with a fixed emissivity index (β = 2). A study of the χ2 distribution indicates that this model is not appropriate in all cases, and this is supported by the FIR colours which indicate a spread in β = 1-2. Statistical comparison of the dust mass and temperature distributions from 140 galaxies with χ2
d.o.f. = 3 < 7.8 (95 per cent confidence level) shows that late types have typically colder, more massive dust reservoirs; the early-type dust masses have a mean of log〈M〉/M = 6.3 ± 0.3, while for late types log〈M〉/M = 7.1 ± 0.1. The late-type dust temperatures have a mean of 〈T〉 = 19.4 ± 0.2 K, while for the early types, 〈T〉 = 21.1 ± 0.8 K. Late-type galaxies in the cluster exhibit slightly lower dust masses than those in the field, but the cluster environment seems to have little effect on the bulk dust properties of early types. In future papers we will focus more on the scientific analysis of the catalogue (e.g. measuring FIR luminosity functions, dust mass functions and resolved gas and dust properties).
ABSTRACT
We present observations of the pulsar-wind nebula (PWN) region of SNR 0540-69.3. The observations were made with the Atacama Compact Array (ACA) in Bands 4 and 6. We also add radio ...observations from the Australia Compact Array at 3 cm. For 1.449–233.50 GHz, we obtain a synchrotron spectrum $F_{\nu } \propto \nu ^{-\alpha _{\nu }}$, with the spectral index αν = 0.17 ± 0.02. To conclude how this joins the synchrotron spectrum at higher frequencies, we include hitherto unpublished AKARI mid-infrared data, and evaluate published data in the ultraviolet (UV), optical, and infrared (IR). In particular, some broad-band filter data in the optical must be discarded from our analysis due to contamination by spectral line emission. For the UV/IR part of the synchrotron spectrum, we arrive at $\alpha _{\nu } = 0.87^{+0.08}_{-0.10}$. There is room for 2.5 × 10−3 M⊙ of dust with a temperature of ∼55 K if there are dual breaks in the synchrotron spectrum, one around ∼9 × 1010 Hz and another at ∼2 × 1013 Hz. The spectral index then changes at ∼9 × 1010 Hz from αν = 0.14 ± 0.07 in the radio to $\alpha _{\nu } = 0.35^{-0.07}_{+0.05}$ in the millimetre-to-far-IR range. The ACA Band 6 data marginally resolve the PWN. In particular, the strong emission $\text{$\sim$} 1\hbox{$.\!\!^{\prime \prime }$}5$ south-west of the pulsar, seen at other wavelengths, and resolved in the 3 cm data with its 0.″8 spatial resolution, is also strong in the millimetre range. The ACA data clearly reveal the supernova remnant shell ∼20–35 arcsec west of the pulsar, and for the shell we derive αν = 0.64 ± 0.05 for the range 8.6–145 GHz.
We describe the Herschel Virgo Cluster Survey and the first data that cover the complete survey area (four 4 × 4 deg2 regions). We use these data to measure and compare the global far-infrared ...properties of 78 optically bright galaxies that are selected at 500 μm and detected in all five far-infrared bands. We show that our measurements and calibration are broadly consistent with previous data obtained by the IRAS, ISO, Spitzer and Planck. We use SPIRE and PACS photometry data to produce 100-, 160-, 250-, 350- and 500-μm cluster luminosity distributions. These luminosity distributions are not power laws, but 'peaked', with small numbers of both faint and bright galaxies. We measure a cluster 100-500 μm far-infrared luminosity density of 1.6(7.0) ± 0.2 × 109 L⊙ Mpc−3. This compares to a cluster 0.4-2.5 μm optical luminosity density of 5.0(20.0) × 109 L⊙ Mpc−3, some 3.2(2.9) times larger than the far-infrared. A 'typical' photon originates from an optical depth of 0.4 ± 0.1. Most of our sample galaxies are well fitted by a single modified blackbody (β= 2), leading to a mean dust mass of log M
Dust= 7.31 M⊙ and temperature of 20.0 K. We also derive both stellar and atomic hydrogen masses from which we calculate mean values for the star-to-gas (atomic) and gas (atomic)-to-dust mass ratios of 15.1 and 58.2, respectively. Using our derived dust, atomic gas and stellar masses, we estimate cluster mass densities of 8.6(27.8) × 106, 4.6(13.9) × 108 and 7.8(29.7) × 109 M⊙ Mpc−3 for dust, atomic gas and stars, respectively. These values are higher than those derived for field galaxies by factors of 39(126), 6(18) and 34(129), respectively. In the above, the luminosity/mass densities are given using the whole sample with the values in brackets using just those galaxies that lie between 17 and 23 Mpc. We provide a data table of flux densities in all the Herschel bands for all 78 bright Virgo Cluster galaxies.
We examined variations in the 160/250 and 250/350 μm surface brightness ratios within 24 nearby (<30 Mpc) face-on spiral galaxies
observed with the Herschel Space Observatory to identify the heating ...mechanisms for dust emitting at these wavelengths. The analysis consisted of both qualitative and quantitative comparisons of the 160/250 and 250/350 μm ratios to Hα and 24 μm emission, which trace the light from star-forming regions, and 3.6 μm emission, which traces the light from the older stellar populations of the galaxies. We find broad variations in the heating mechanisms for the dust. In one subset of galaxies, we found evidence that emission at ≤160 μm (and in rare cases potentially at ≤350 μm) originates from dust heated by star-forming regions. In another subset, we found that the emission at ≥250 μm (and sometimes at ≥160 μm) originates from dust heated by the older stellar population. In the rest of the sample, either the results are indeterminate or both of these stellar populations may contribute equally to the global dust heating. The observed variations in dust heating mechanisms do not necessarily match what has been predicted by dust emission and radiative transfer models, which could lead to overestimated dust temperatures, underestimated dust masses, false detections of variability in dust emissivity, and inaccurate star formation rate measurements.
Using the IRAM NOrthern Extended Millimetre Array (NOEMA), we conducted a Large Programme (z-GAL) to measure redshifts for 126 bright galaxies detected in the Herschel Astrophysical Large Area Survey ...(H-ATLAS), the HerMES Large Mode Survey (HeLMS), and the Herschel Stripe 82 (HerS) Survey. We report reliable spectroscopic redshifts for a total of 124 of the Herschel-selected galaxies. The redshifts are estimated from scans of the 3 and 2-mm bands (and, for one source, the 1-mm band), covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. Together with the Pilot Programme, where 11 sources had their spectroscopic redshifts measured, our survey has derived precise redshifts for 135 bright Herschel-selected galaxies, making it the largest sample of high-z galaxies with robust redshifts to date. Most emission lines detected are from 12 CO (mainly from J = 2-1 to 5-4), with some sources seen in CI and H 2 O emission lines. The spectroscopic redshifts are in the range 0.8 < z < 6.55 with a median value of z = 2.56 ± 0.10, centred on the peak epoch of galaxy formation. The linewidths of the sources are large, with a mean value for the full width at half maximum ∆V of 590 ± 25 km s −1 and with 35% of the sources having widths of 700 km s −1 < ∆V < 1800 km s −1. Most of the sources are unresolved or barely resolved on scales of ∼2 to 3 (or linear sizes of ∼15−25 kpc, unlensed). Some fields reveal double or multiple sources in line emission and the underlying dust continuum and, in some cases, sources at different redshifts. Taking these sources into account, there are, in total, 165 individual sources with robust spectroscopic redshifts, including lensed galaxies, binary systems, and over-densities. This paper presents an overview of the z-GAL survey and provides the observed properties of the emission lines, the derived spectroscopic redshifts, and a catalogue of the entire sample. The catalogue includes, for each source, the combined continuum and emission lines' maps together with the spectra for each of the detected emission lines. The data presented here will serve as a foundation for the other z-GAL papers in this series reporting on the dust emission, the molecular and atomic gas properties, and a detailed analysis of the nature of the sources. Comparisons are made with other spectroscopic surveys of high-z galaxies and future prospects, including dedicated follow-up observations based on these redshift measurements, are outlined.
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