We investigate the potential for the emission lines OV] $λλ$1213.8,1218.3 and HeII $λ$1215.1 to contaminate flux measurements of Ly$α$ $λ$1215.7 in the extended nebulae of quasars. We have computed a grid of photoionization models with a substantial range in the slope of the ionizing powerlaw (-1.5 $<$ $α$ $<$ -0.5), gas metallicity (0.01 $<$ $Z/Z_{\odot}$ $<$ 3.0), gas density (1 $<$ $n_H$ $<$ 10$^4$ cm$^{-3}$), and ionization parameter (10$^{-5}$ $<$ U $<$ 1.0). We find the contribution from HeII $λ$1215.1 to be negligible, i.e., $<$ 0.1 of Ly$α$ flux, across our entire model grid. The contribution from OV] $λλ$1213.8,1218.3 is generally negligible when U is low (<10$^{-3}$) and/or when the gas metallicity is low ($Z/Z_{\odot}$ < 0.1). However, at higher values of U and Z we find that OV] can significantly contaminate Ly$α$, in some circumstances accounting for more than half the total flux of the Ly$α$+HeII+OV] blend. We also provide means to estimate the fluxes of OV] $λλ$1213.8,1218.3 and HeII $λ$1215.1 by extrapolating from other lines. We estimate the fluxes of OV] and HeII for a sample of 107 Type 2 active galaxies at z$>$2, and find evidence for significant (>10\%) contamination of Ly$α$ fluxes in the majority of cases (84\%). We also discuss prospects for using OV] $λλ$1213.8,1218.3 as a diagnostic for the presence of AGN activity in high-z Ly$α$ emitters, and caution that the presence of significant OV] emission could impact the apparent kinematics of Ly$α$, potentially mimicking the presence of high-velocity gas outflows.
In this paper, we present a Ly$α$ halo extended to $\sim200$ kpc identified by stacking $\sim 3300$ Ly$α$ emitters at $z=2.2-2.3$. We carry out imaging observations and data reduction with Subaru/Hyper Suprime-Cam (HSC). Our total survey area is $\sim12$ deg$^2$ and imaging depths are $25.5-27.0$ mag. Using the imaging data, we select 1,240 and 2,101 LAE candidates at $z=2.2$ and 2.3, respectively. We carry out spectroscopic observations of our LAE candidates and data reduction with Magellan/IMACS to estimate the contamination rate of our LAE candidates. We find that the contamination rate of …
New results are presented, as part of the Hi-z Emission Line Survey (HiZELS), from the largest area survey to date (1.4 sq.deg) for Lyman-alpha emitters (LAEs) at z~9. The survey, which is primarily targeting H-alpha emitters at z<3, uses the Wide Field CAMera on the United Kingdom Infrared Telescope and a custom narrow-band filter in the J band and reaches a Lyman-alpha luminosity limit of ~10^43.8 erg/s over a co-moving volume of 1.12x10^6 Mpc^3 at z=8.96+-0.06. Only 2 candidates were found out of 1517 line emitters and those were rejected as LAEs after follow-up observations. The limit on t…
We report Atacama Large Millimetre/submillimeter Array (ALMA) Cycle-5 follow-up observations of two candidate [CII] emitters at z ~ 6 in the ALMA deep field in SSA22 (ADF22). The candidates were detected blindly in a Cycle-2 ALMA survey covering ~ 5 square arcmins, with a single tuning, along with two CO lines associated with galaxies at lower redshifts. Various tests suggested at least one of the two > 6-sigma [CII] candidates should be robust (Hayatsu et al. 2017). Nevertheless, our new, deeper observations recover neither candidate, demonstrating a higher contamination rate than expected. T…
Planetary nebulae (PNe) are strong H$α$ line-emitters and a lot of new PNe discoveries have been made by the SuperCOSMOS AAO/UKST H$α$ Survey (SHS) and the Isaac Newton Telescope Photometric H$α$ Survey (IPHAS). However, the list of auto-generated H$α$-excess candidates from these surveys as well as any photometric survey, prior to spectroscopic follow-up to confirm their nature, contains all varieties of H$α$-line emitters like young stellar objects (YSOs), H II regions, compact PNe and emission line stars of all kinds. The aim of this work is to find new infrared criteria that can better dis…
We present the results of an unbiased search for Lyα emission from continuum-selected 6 < z < 8 galaxies. Our dataset consists of 160 orbits of G102 slitless grism spectroscopy obtained with the Hubble Space Telescope (HST) Wide Field Camera 3 as part of the Faint Infrared Grism Survey (FIGS; PI: Malhotra), which obtains deep slitless spectra of all sources in four fields, and was designed to minimize contamination in observations of previously-identified high-redshift galaxy candidates. The FIGS data can potentially spectroscopically confirm the redshifts of galaxies, and as Lyα emission is r…
The derivation of abundances in gaseous nebulae ionised by massive stars using optical collisionally excited emission lines is studied in this work comparing the direct or $T_e$ method with updated grids of photoionisation models covering a wide range of input conditions of O/H and N/O abundances and ionisation parameter. The abundances in a large sample of compiled objects with at least one auroral line are re-derived and later compared with the $χ^2$ weighted-mean abundances from the models. The agreement between the abundances using the two methods both for O/H and N/O is excellent with no …
Context. Lyman Break Galaxies (LBG) and Narrow Band (NB) surveys have been successful at detecting large samples of high-redshift galaxies. Both methods are subject to contamination from low-redshift interlopers. Aims. In this paper, our aim is to investigate the nature of low-redshift interlopers in NB Lyman-$α$ emitters (LAE) searches. Methods. From previous HAWK-I NB imaging at z $\sim$7.7 we identify three objects that would have been selected as high-redshift LAEs had our optical data been one magnitude shallower (but still one to two magnitudes fainter than the near infrared data). We fo…
Mid-IR observations of planetary nebulae (PNe) have revealed diffuse emission associated to their main nebular shells and outer envelopes or haloes. The interpretation of this emission is uncertain because the broad-band mid-IR images may include contributions of different components. In particular, the Spitzer IRAC 8 μm images, that best reveal these nebular features, can include contributions not only of H2 lines, but also those of ionic species, PAH features, and thermal dust continuum emission. To investigate the nature of the emission detected in mid-IR observations of a sample of 10 PNe,…
The SMC harbours a class of hot nitrogen-sequence Wolf-Rayet stars (WNE) that display only relatively weak broad emission lines. This indicates low mass-loss rates and makes them also hard to detect. However, such stars are possible emitters of strong He+ Lyman continua that in turn could ionize observable HeIII regions, i.e. highly excited HII regions emitting nebular HeII4686 emission. We here report the discovery of a rare HeIII region in the SMC which is located in the OB association NGC249 around the weak-lined WN star SMC WR10. WR10 is particularly interesting since it is a single star s…
We introduce a method of subtracting geocoronal Halpha emissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae (LAMOST-MRS-N). The flux ratios of the Halpha sky line to the adjacent OH lambda6554 single line do not show a pattern or gradient distribution in a plate. More interestingly, the ratio is well correlated to solar altitude, which is the angle of the sun relative to the Earth's horizon. It is found that the ratio decreases from 0.8 to 0.2 with the decreasing solar altitude from -17 to -73 degree. Based on this relation, which is described by a linear …
We explore the so-called softness diagram -- whose main function is to provide the hardness of the ionizing radiation in star-forming regions -- in order to check whether hot and old low-mass evolved stars (HOLMES) are significant contributors to the ionization within star-forming regions, as suggested by previous MaNGA data analyses. We used the code HCm-Teff to derive both the ionization parameter and the equivalent effective temperature (T*), adopting models of massive stars and planetary nebulae (PNe), and exploring different sets of emission lines in the softness diagram to figure out the…
Extragalactic planetary nebulae (PNe) are detectable through relatively strong nebulous [OIII] emission and act as direct probes into the local stellar population. Because they have an apparently universal invariant magnitude cut-off, PNe are also considered to be a remarkable standard candle for distance estimation. Through detecting PNe within the galaxies, we aim to connect the relative abundances of PNe to the properties of their host galaxy stellar population. By removing the stellar background components from FCC 167 and FCC 219, we aim to produce PN luminosity functions (PNLF) of these …
We report the detection of diffuse Ly$α$ emission, or Ly$α$ halos (LAHs), around star-forming galaxies at $z\approx3.78$ and $2.66$ in the NOAO Deep Wide-Field Survey Boötes field. Our samples consist of a total of $\sim$1400 galaxies, within two separate regions containing spectroscopically confirmed galaxy overdensities. They provide a unique opportunity to investigate how the LAH characteristics vary with host galaxy large-scale environment and physical properties. We stack Ly$α$ images of different samples defined by these properties and measure their median LAH sizes by decomposing the st…
Ly$α$ $λ$1216 (Ly$α$) emission extending over $\gtrsim\,\rm 10\,kiloparsec\,(kpc)$ around dusty, massive starbursts at $z\gtrsim3$ might represent a short-lived phase in the evolution of present-day, massive quiescent galaxies. To obtain empirical constraints on this emerging scenario, we present Ly$α$, CIV $λ$1550 (CIV), and HeII $λ$1640 (HeII) observations taken with the Multi Unit Spectroscopic Explorer towards J1000$+$0234: a galaxy pair at $z=4.5$ composed of a low-mass starburst (J1000$+$0234$-$South) neighboring a massive Submillimeter Galaxy (SMG; J1000$+$0234$-$North) that harbors a r…
We present an investigation on escape fractions of UV photons from a unique sample of lensed low-mass emission line selected galaxies at z < 3.5 found in the SHARDS Hubble Frontier Fields medium-band survey. We have used this deep imaging survey to locate 42 relatively low-mass galaxies, down to $log(M_{*}/M_{\odot}) = 7$, between redshifts 2.4 < z < 3.5 which are candidate line emitters. Using deep multi-band Hubble UVIS imaging we investigate the flux of escaping ionizing photons from these systems, obtaining 1$σ$ upper limits of $f^{rel}_{esc}$ ~7% for individual galaxies, and < 2% for stac…
We present new diagnostic tools for distinguishing supernova remnants (SNRs) from HII regions. Up to now, sources with flux ratio [S II]/H$\rmα$ higher than 0.4 have been considered as SNRs. Here, we present the combinations of three or two line ratios as more effective tools for the separation of these two kinds of nebulae, depicting them as 3D surfaces or 2D lines. The diagnostics are based on photoionization and shock excitation models (MAPPINGS III) analysed with Support Vector Machine (SVM) models for classification. The line-ratio combination that gives the most efficient diagnostic is: …
We present basic properties of $\sim$3,300 emission line galaxies detected by the FastSound survey, which are mostly H$α$ emitters at $z \sim$ 1.2-1.5 in the total area of about 20 deg$^2$, with the H$α$ flux sensitivity limit of $\sim 1.6 \times 10^{-16} \rm erg \ cm^{-2} s^{-1}$ at 4.5 sigma. This paper presents the catalogs of the FastSound emission lines and galaxies, which will be open to the public in the near future. We also present basic properties of typical FastSound H$α$ emitters, which have H$α$ luminosities of $10^{41.8}$-$10^{43.3}$ erg/s, SFRs of 20--500 $M_\odot$/yr, and stella…
ODIN: Using multiplicity of Lyman-Alpha Emitters to assess star formation activity in dark matter halos
Instituto de Astronomía Teórica y Experimental (IATE), CONICET-UNC（理论与实验天体物理学研究所）；Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba（科尔多瓦国立大学数学、天文学、物理与计算学院）；Observatorio Astronómico de Córdoba, Universidad Nacional de Córdoba（科尔多瓦天文台）；Rutgers, the State University of New Jersey（新泽西州立罗格斯大学）；Universidad Andres Bello（安德斯·贝略大学）；Purdue University（普渡大学）；Korea Institute for Advanced Study（韩国高等研究院）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；The Pennsylvania State University（宾夕法尼亚州立大学）；Millennium Nucleus for Galaxies (MINGAL)（星系千年核心研究组）；Seoul National University（首尔大学）；Australian Astronomical Optics - Macquarie University（澳大利亚天文光学-麦考瑞大学）；Universidad Central de Chile（智利中央大学）；University of Arizona（亚利桑那大学）
A Single Line-Emitter Identified in an Unbiased Search with JWST/NIRSpec: Multi-Object Coronagraphy for Slitless Spectroscopy
University of Minnesota（明尼苏达大学）；Stockholm University（斯德哥尔摩大学）；Space Telescope Science Institute（太空望远镜科学研究所）；University of Texas at Austin（德克萨斯大学奥斯汀分校）；University of Modena & Reggio Emilia（摩德纳与雷焦艾米利亚大学）；University College London（伦敦大学学院）；Williams College（威廉姆斯学院）
NGC 6946, known as the Fireworks galaxy because of its high supernova rate and high star formation, is embedded in a very extended HI halo. Its northern spiral arm is well detached from the galactic main body. We found that this arm contains a large (~300 pc in size) Red Ellipse, named according to a strong contamination of the H-alpha emission line on its optical images. The ellipse is accompanied by a short parallel arc and a few others still smaller and less regular; a bright star cluster is seen inside these features. The complicated combination of arcs seems to be unique, it is only a bit…
We present a narrow-band imaging survey of the Large Magellanic Cloud, designed to isolate the C II $λλ$7231, 7236 emission lines in objects as faint as $m_{\lambda7400}\sim18$. The work is motivated by the recent serendipitous discovery in the LMC of the first confirmed extragalactic [WC11] star, whose spectrum is dominated by C II emission, and the realization that the number of such objects is currently largely unconstrained. The survey, which imaged $\sim$50$~$deg$^2$ using on-band and off-band filters, will significantly increase the total census of these rare stars. In addition, each new…
We present a study of the environment of 27 z=3-4.5 bright quasars from the MUSE Analysis of Gas around Galaxies (MAGG) survey. With medium-depth MUSE observations (4 hours on target per field), we characterise the effects of quasars on their surroundings by studying simultaneously the properties of extended gas nebulae and Lyalpha emitters (LAEs) in the quasar host haloes. We detect extended (up to ~ 100 kpc) Lyalpha emission around all MAGG quasars, finding a very weak redshift evolution between z=3 and z=6. By stacking the MUSE datacubes, we confidently detect extended emission of CIV and o…
This paper presents a detailed analysis of two giant Lyman-alpha (Lya) arcs detected near known galaxies at z=3.038 and z=3.754 lensed by the massive cluster MACS 1206 (z=0.44). The Lya nebulae revealed in deep MUSE observations exhibit a double-peak profile with a dominant red peak that indicates expansion/outflowing motions. One of the arcs stretches over 1' around the Einstein radius of the cluster, resolving the velocity field of the line-emitting gas on kpc scales around a group of three star-forming galaxies of 0.3-1.6L* at z=3.038. The second arc spans 15'' in size, roughly centered aro…
We report the detection of extended warm ionized gas in two powerful high-redshift radio galaxies, NVSS J210626-314003 at z=2.10 and TXS 2353-003 at z=1.49, that does not appear to be associated with the radio jets. This is contrary to what would be expected from the alignment effect, a characteristic feature of distant, powerful radio galaxies at z> 0.6. The gas also has smaller velocity gradients and line widths than most other high-z radio galaxies with similar data. Both galaxies are part of a systematic study of 50 high-redshift radio galaxies with SINFONI, and are the only two that are c…
Water fountain stars represent a stage between the asymptotic giant branch (AGB) and planetary nebulae phases, when the mass loss changes from spherical to bipolar. These types of evolved objects are characterized by high-velocity jets in the 22 GHz water maser emission. We surveyed the CO and 13CO line emission towards a sample of ten water fountain stars through observing the J=1-0 and 2-1 lines of CO and 13CO, using the 30m IRAM radio telescope at Pico Veleta. All the water fountains visible from the observatory were surveyed. Most of the line emission arises from foreground or background G…
The Lya emission line of HI is intrinsically the brightest feature in the spectrum of astrophysical nebulae, making it a very attractive observational tool with which to survey galaxies. Moreover as a UV resonance line, Lya possesses several unique characteristics that make it useful to study the ISM and ionizing stellar population at all cosmic epochs. In this review I present a summary of Lya observations of galaxies in the nearby universe. At UV magnitudes reachable with current facilities, only ~5% of the local galaxy population shows a Lya equivalent width (EW_Lya) that exceeds 20Å. This …
The systematic targeting of extended Ly$α$ emission around high-redshift quasars resulted in the discovery of rare and bright Enormous Ly$α$ Nebulae (ELANe) associated with multiple active galactic nuclei (AGN). We here initiate "a multiwavelength study of ELAN environments" (AMUSE$^2$) focusing on the ELAN around the $z\sim3$ quasar SDSS J1040+1020, a.k.a. the Fabulous ELAN. We report on VLT/HAWK-I, APEX/LABOCA, JCMT/SCUBA-2, SMA/850$μ$m, ALMA/CO(5-4) and 2mm observations and compare them to previously published VLT/MUSE data. The continuum and line detections enable a first estimate of the s…
We present a Bayesian approach to the redshift classification of emission-line galaxies when only a single emission line is detected spectroscopically. We consider the case of surveys for high-redshift Lyman-alpha-emitting galaxies (LAEs), which have traditionally been classified via an inferred rest-frame equivalent width (EW) greater than 20 angstrom. Our Bayesian method relies on known prior probabilities in measured emission-line luminosity functions and equivalent width distributions for the galaxy populations, and returns the probability that an object in question is an LAE given the cha…
The mutually complementary Euclid and Roman galaxy redshift surveys will use Halpha- and [OIII]-selected emission line galaxies as tracers of the large scale structure at $0.9 \lesssim z \lesssim 1.9$ (Halpha) and $1.5 \lesssim z \lesssim 2.7$ ([OIII]). It is essential to have a reliable and sufficiently precise knowledge of the expected numbers of Halpha-emitting galaxies in the survey volume in order to optimize these redshift surveys for the study of dark energy. Additionally, these future samples of emission-line galaxies will, like all slitless spectroscopy surveys, be affected by a compl…
