Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCharacterizing elusive, faint dusty star-forming galaxies: a lensed, optically undetected ALMA galaxy at z~3.3
92
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present the serendipitous ALMA detection of a faint submillimeter galaxy (SMG) lensed by a foreground z~1 galaxy. By optimizing the source detection to deblend the system, we accurately build the full spectral energy distribution of the distant galaxy from the I814 band to radio wavelengths. It is extremely red, with a I-K colour larger than 2.5. We estimate a photometric redshift of 3.28 and determine the physical parameters. The distant galaxy turns out to be magnified by the foreground lens by a factor of ~1.5, which implies an intrinsic Ks-band magnitude of ~24.5, a submillimeter flux at 870um of ~2.5 mJy and a SFR of ~150-300Msun/yr, depending on the adopted tracer. These values place our source towards the faint end of the distribution of observed SMGs, and in particular among the still few faint SMGs with a fully characterized spectral energy distribution, which allows us not only to accurately estimate its redshift but also to measure its stellar mass and other physical properties. The galaxy studied in this work is a representative of the population of faint SMGs, of which only few objects are known to date, that are undetected in optical and therefore are not typically accounted for when measuring the cosmic star formation history (SFH). This faint galaxy population thus likely represents an important and missing piece in our understanding of the cosmic SFH. Its observation and characterization is of major importance to achieve a solid picture of galaxy evolution.
rate research
Read More
We report the detection of a massive neutral gas outflow in the z=2.09 gravitationally lensed Dusty Star-Forming Galaxy HATLASJ085358.9+015537 (G09v1.40), seen in absorption with the OH+(1_1-1_0) transition using spatially resolved (0.5x0.4) Atacama Large Millimeter/submillimeter Array (ALMA) observations. The blueshifted OH+ line is observed simultaneously with the CO(9-8) emission line and underlying dust continuum. These data are complemented by high angular resolution (0.17x0.13) ALMA observations of CH+(1-0) and underlying dust continuum, and Keck 2.2 micron imaging tracing the stellar emission. The neutral outflow, dust, dense molecular gas and stars all show spatial offsets from each other. The total atomic gas mass of the observed outflow is 6.7x10^9 M_sun, >25% as massive as the gas mass of the galaxy. We find that a conical outflow geometry best describes the OH+ kinematics and morphology and derive deprojected outflow properties as functions of possible inclination (0.38 deg-64 deg). The neutral gas mass outflow rate is between 83-25400 M_sun/yr, exceeding the star formation rate (788+/-300 M_sun/yr) if the inclination is >3.6 deg (mass-loading factor = 0.3-4.7). Kinetic energy and momentum fluxes span 4.4-290x10^9 L_sun and 0.1-3.7x10^37 dyne, respectively (energy-loading factor = 0.013-16), indicating that the feedback mechanisms required to drive the outflow depend on the inclination assumed. We derive a gas depletion time between 29 and 1 Myr, but find that the neutral outflow is likely to remain bound to the galaxy, unless the inclination is small, and may be re-accreted if additional feedback processes do not occur.
We present ci,(2--1) and multi-transition $^{12}$CO observations of a dusty star-forming galaxy, ACT,J2029+0120, which we spectroscopically confirm to lie at $z$,=,2.64. We detect CO(3--2), CO(5--4), CO(7--6), CO(8--7), and ci,(2--1) at high significance, tentatively detect HCO$^{+}$(4--3), and place strong upper limits on the integrated strength of dense gas tracers (HCN(4--3) and CS(7--6)). Multi-transition CO observations and dense gas tracers can provide valuable constraints on the molecular gas content and excitation conditions in high-redshift galaxies. We therefore use this unique data set to construct a CO spectral line energy distribution (SLED) of the source, which is most consistent with that of a ULIRG/Seyfert or QSO host object in the taxonomy of the textit{Herschel} Comprehensive ULIRG Emission Survey. We employ RADEX models to fit the peak of the CO SLED, inferring a temperature of T$sim$117 K and $n_{text{H}_2}sim10^5$ cm$^{-3}$, most consistent with a ULIRG/QSO object and the presence of high density tracers. We also find that the velocity width of the ci line is potentially larger than seen in all CO transitions for this object, and that the $L_{rm C,I(2-1)}/L_{rm CO(3-2)}$ ratio is also larger than seen in other lensed and unlensed submillimeter galaxies and QSO hosts; if confirmed, this anomaly could be an effect of differential lensing of a shocked molecular outflow.
Water ($rm H_{2}O$), one of the most ubiquitous molecules in the universe, has bright millimeter-wave emission lines easily observed at high-redshift with the current generation of instruments. The low excitation transition of $rm H_{2}O$, p$-$$rm H_{2}O$(202 $-$ 111) ($ u_{rest}$ = 987.927 GHz) is known to trace the far-infrared (FIR) radiation field independent of the presence of active galactic nuclei (AGN) over many orders-of-magnitude in FIR luminosity (L$_{rm FIR}$). This indicates that this transition arises mainly due to star formation. In this paper, we present spatially ($sim$0.5 arcsec corresponding to $sim$1 kiloparsec) and spectrally resolved ($sim$100 kms$^{-1}$) observations of p$-$$rm H_{2}O$(202 $-$ 111) in a sample of four strong gravitationally lensed high-redshift galaxies with the Atacama Large Millimeter/submillimeter Array (ALMA). In addition to increasing the sample of luminous ($ > $ $10^{12}$L$_{odot}$) galaxies observed with $rm H_{2}O$, this paper examines the L$_{rm H_{2}O}$/L$_{rm FIR}$ relation on resolved scales for the first time at high-redshift. We find that L$_{rm H_{2}O}$ is correlated with L$_{rm FIR}$ on both global and resolved kiloparsec scales within the galaxy in starbursts and AGN with average L$_{rm H_{2}O}$/L$_{rm FIR}$ =$2.76^{+2.15}_{-1.21}times10^{-5}$. We find that the scatter in the observed L$_{rm H_{2}O}$/L$_{rm FIR}$ relation does not obviously correlate with the effective temperature of the dust spectral energy distribution (SED) or the molecular gas surface density. This is a first step in developing p$-$$rm H_{2}O$(202 $-$ 111) as a resolved star formation rate (SFR) calibrator.
We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 micrometer imaging of four high-redshift (z=2.8-5.7) dusty sources that were detected using the South Pole Telescope (SPT) at 1.4 mm and are not seen in existing radio to far-infrared catalogs. At 1.5 arcsec resolution, the ALMA data reveal multiple images of each submillimeter source, separated by 1-3 arcsec, consistent with strong lensing by intervening galaxies visible in near-IR imaging of these sources. We describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self-calibration-like antenna phase corrections as part of the model optimization, which we use to interpret the source structure. Lens models indicate that SPT0346-52, located at z=5.7, is one of the most luminous and intensely star-forming sources in the universe with a lensing corrected FIR luminosity of 3.7 X 10^13 L_sun and star formation surface density of 4200 M_sun yr^-1 kpc^-2. We find magnification factors of 5 to 22, with lens Einstein radii of 1.1-2.0 arcsec and Einstein enclosed masses of 1.6-7.2x10^11 M_sun. These observations confirm the lensing origin of these objects, allow us to measure the their intrinsic sizes and luminosities, and demonstrate the important role that ALMA will play in the interpretation of lensed submillimeter sources.
We present first results from the SXDF-ALMA 1.5 arcmin^2 deep survey at 1.1 mm using Atacama Large Millimeter Array (ALMA). The map reaches a 1sigma depth of 55 uJy/beam and covers 12 Halpha-selected star-forming galaxies at z = 2.19 or z=2.53. We have detected continuum emission from three of our Halpha-selected sample, including one compact star-forming galaxy with high stellar surface density, NB2315-07. They are all red in the rest-frame optical and have stellar masses of log (M*/Msun)>10.9 whereas the other blue, main-sequence galaxies with log(M*/Msun)=10.0-10.8 are exceedingly faint, <290 uJy (2sigma upper limit). We also find the 1.1 mm-brightest galaxy, NB2315-02, to be associated with a compact (R_e=0.7+-0.1 kpc), dusty star-forming component. Given high gas fraction (44^{+20}_{-8}% or 37^{+25}_{-3}%) and high star formation rate surface density (126^{+27}_{-30} Msun yr^{-1}kpc^{-2}), the concentrated starburst can within less than 50^{+12}_{-11} Myr build up a stellar surface density matching that of massive compact galaxies at z~2, provided at least 19+-3% of the total gas is converted into stars in the galaxy centre. On the other hand, NB2315-07, which already has such a high stellar surface density core, shows a gas fraction (23+-8%) and is located in the lower envelope of the star formation main-sequence. This compact less star-forming galaxy is likely to be in an intermediate phase between compact dusty star-forming and quiescent galaxies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
